INTERNATIONAL COURT OF JUSTICEDISPUTE OVER THE STATUS AND USE OF THE WATERS OF THE SILALA(CHILE v. BOLIVIA)MEMORIAL OF THEREPUBLIC OF CHILEANNEXES I-IIITO THE EXPERT REPORTS VOLUME 4OF 63 JULY 2017
ANNEX NO.TITLEPAGE NO.VOLUME 4ANNEXES TO THE EXPERT REPORTS (ANNEXES I-III)Annex IAlcayaga, H., 2017. Characterization of the Drainage Patterns and River Network of the SilalaRiver and Preliminary Assessment of Vegetation Dynamics Using Remote Sensing1Annex IIArcadis, 2017. Detailed Hydrogeological Study of the Silala River91Annex IIIHerrera, C. and Aravena, R., 2017. Chemical and Isotopic Characterization of Surface Water and Groundwater of the Silala Transboundary Basin, Second Region, Chile487
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Alcayaga, H., 2017. Characterization of the Drainage Patterns and River Network of the Silala River and Preliminary Assessment of Vegetation Dynamics Using Remote Sensing
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ANNEX I
CHARACTERIZATION OF THE DRAINAGE PATTERNS AND RIVER
NETWORK OF THE SILALA RIVER AND PRELIMINARY ASSESSMENT
OF VEGETATION DYNAMICS USING REMOTE SENSING
Hernán Alcayaga S. (PhD)
Assistant Professor, Universidad Diego Portales
May, 2017
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Glossary Aquifer Recharge: syn. Groundwater recharge or recharge. Natural or artificial introduction of water into the saturated zone of an aquifer. Catchment Area: see Watershed. Drainage Network: see Drainage Pattern. Drainage Pattern: syn. Channel network, see also hydrographical network. Layout of natural and/or man-made drainage channels within an area. Dryland Vegetation: Is the vegetation present in drylands. In dryland or arid ecosystems the annual rainfall is less than 200 mm/yr. (McGinnies et al., 1968). Ephemeral Gullying Potential: The potential water erosion due to gully formation by runoff and/or during the melting of snow concentration. Ephemeral Stream: An ephemeral stream is one that remains dry during some of the year. Flow can result from a rising water table intersecting the stream-bed or from periods of surface flow. Exorheic Watershed: Watershed which is externally drained, having one or more outlets. Green Biomass: The total amount of living plants and algae of the type Viridiplantae (green) in a given area. Green Leaf Area Index or “Leaf Area Index” (LAI): Is an index to express the area of leaf surface (one surface only) in a stand covering a unit area of land surface (Watson, 1947). Headwater Streams: A tributary stream of a river, close to or forming part of its source. Nickpoint: Abrupt change of gradient in the profile of a stream or river, typically due to a change in the rate of erosion. Overland Flow: syn. Hortonian flow see also surface flow. Flow of water over the ground surface before it enters a defined channel. Perennial Stream: Stream which flows continuously all through the year. Perennial Vegetation: Is vegetation with a life span extending over more than two growing seasons. cf. annual, biennial. River Basin: see Watershed. 4
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River Discharge: syn. Rate of flow in a river. Volume of water flowing through a river
(or channel) cross-section per unit time.
River Network: syn. Hydrographical network. Aggregate of rivers and other permanent
or temporary watercourses, and also lakes and reservoirs, over any given area.
Water Erosion: Wearing away and transport of soil and rock by running water.
Watershed: Basin syn. drainage basin, catchment, river basin. Area having a common
outlet for its surface runoff.
Wetland: Area of marsh, fen, peatland or water – whether natural or artificial,
permanent or temporary – with water that is static or flowing, fresh, brackish or salt,
including areas of marine water the depth of which does not exceed six meters at low
tide.
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TABLE OF CONTENTS 1.INTRODUCTION ..................................................................................................... 11.1. Presentation ........................................................................................................ 1 1.2. Location of the investigated area........................................................................ 2 1.3. Objectives ........................................................................................................... 4 1.4. Summary of the methodology ............................................................................ 4 1.5. Structure of the report......................................................................................... 5 2.SUMMARY AND CONCLUSIONS ........................................................................ 53.BACKGROUND AND INFORMATION SOURCES ............................................. 64.METHODOLOGY .................................................................................................. 105.RESULTS ................................................................................................................ 125.1. Watershed delineation and drainage network extraction ................................. 12 5.2. Comparison between the channel network extracted from GIS methods and the Chilean and Bolivian official cartography .................................................................. 16 5.3. Comparison between the river networks extracted from GIS methods and aerial photographs ................................................................................................................. 20 5.4. The Compound Topographic Index ................................................................. 27 5.5. Analysis of the evolution of the spatial extent of the Silala highland Andean wetlands ...................................................................................................................... 30 6.CONCLUSIONS AND REMARKS ....................................................................... 337.REFERENCES ........................................................................................................ 35APPENDIX A ................................................................................................................. 39 APPENDIX B ................................................................................................................. 45 APPENDIX C ................................................................................................................. 75 6
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1. INTRODUCTION
1.1. Presentation
This report was requested by the Dirección Nacional de Fronteras y Límites del Estado
(DIFROL) of the Ministry of Foreign Affairs of Chile and was undertaken by Professor
Hernán Alcayaga Saldías (Civil engineer and Docteur en Sciences de la Terre,
l’Univers et l’Environnement, with an academic specialization in hydrology). This work
was developed under the advice and supervision of Professors Howard Wheater and
Denis Peach.
This report is divided into two main parts which are defined as follows:
i. Drainage patterns and river network
The main force responsible for surface water motion (rivers, streams and surface runoff)
is the force of gravity. Basically, the runoff in streams and on hill-slopes occurs when
the force associated with the gravitational field exceeds the total external force due to
frictional resistance, acting along the contact surface between the water and the
boundary (Chow, 1959; Dey et al., 2014). Consequently, an important characteristic of a
river system is its topographic catchment area. The United States Geological Survey
(USGS) defined a watershed as “the area of land where all of the water that falls in it
and drains off of it goes to a common outlet” (USGS, 2016). However, this surface
water catchment area is not necessarily the same as the area contributing groundwater to
the river system. The first part of this report is related to the surface water catchment
area of the Silala River.
In the case of the Silala, the outlet point for delineation of watershed is located close to
the Inacaliri Police Station in the area called Inacaliri. This point was selected as a
suitable location to capture cross-border topographic flow paths, and also because all of
the hydraulic works associated with the historical and current water withdrawals
(aqueducts, canals, water intakes and reservoirs) are located upstream of this point.
For the delineation of the Silala River at Inacaliri, different sources of information give
different interpretations of the catchment area. These sources include historical Chilean
and Bolivian mapping, aerial photography, as well as remote sensing derived Digital
Elevation Models (DEM). This report reviews these differences and uses new,
independent, remote sensing sources to provide a high resolution DEM and the best
current estimate of the topographic catchment area with quantified uncertainty.
A high resolution DEM provides the data needed to define topographic gradients and to
quantify various features of the landscape, including drainage networks and topographic
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2 convergence. This report defines the drainage network for the watershed and shows that the natural gradients of the main channels are such that water flows naturally from Bolivia to Chile in the Silala River system. Other landscape features of relevance to hydrology include measures of topographic convergence, which are indicative of areas where hillslope runoff processes converge to produce stream flow and hence water source areas. This report uses one such index to show that this hillslope runoff convergence is consistent with the location of the Bolivian wetlands. ii.Wetland vegetation dynamicsThe second part of this report is an analysis of the wetland vegetation. An important part of the Silala River system is its water sources, located in two wetland areas in the Bolivian territory. An assessment of the temporal variability of the wetland vegetation areas is relevant in order to understand the behavior of the water sources of this fluvial system. The available satellite imagery is used to define the temporal dynamics of the wetland vegetation. These wetlands correspond to the areas called Cajones and Orientales. 1.2. Location of the investigated area The area investigated corresponds to the Silala River watershed, which is presented in Figure 1. This fluvial system is located in the Bolivian and Chilean territories, between Latitude 21.94° and 22.07° South and Longitude 68.08° and 67.94° West. This drainage area is a sub-basin of the Loa River basin. 8
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Figure 1. Silala watershed location in the international context and as part of the Loa River
network.
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4 1.3. Objectives This Report has two main objectives: i.To show, through a high-resolution digital terrain model analysis, whether theSilala River flows from its source in Bolivia to the Chilean territory to form anexoreic drainage watershed.ii.To analyze the temporal variability of the wetland vegetation areas located in theBolivian territory.In order to achieve these two main objectives, we must first meet the following specific objectives: •To identify all surface flow directions (overland flow) based on a high-resolution digital terrain model.•To delineate the Silala watershed at Inacaliri, considering the surface flowdirections.•To obtain a topographic-based estimate of surface flow accumulation related tothe channel formation, and to extract the river network of the watershed, basedon the criterion of the threshold of flow accumulation.•To verify the consistency of the results (river network extracted from the digitalterrain model), comparing them with official cartography maps, aerialphotography and other relevant hydrological indices.•To collect aerial images of the wetlands areas for different dates, classify themaccording to the vegetation characteristics and determine the correspondingareas of this classification.1.4. Summary of the methodology For a correct delineation of the Silala River watershed a DEM of 5m resolution (DEM-5m) was used and analyzed with a Geographic Information System (GIS) platform. The surface flow patterns were identified (the paths of the overland flow and streamflow), through the use of standardized tools, approved by the professional and scientific community in the water resources field and specifically in the hydrology field. The river network extracted from the DEM-5m was compared against the Bolivian and Chilean official maps and aerial photography. Additionally, the Compound Topographic Index (CTI) was calculated in order to quantify the potential for channel formation and validate the river network. 10
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Finally, for the study of the evolution of the surface extent of the highland Andean
wetlands, the Normalized Difference Vegetation Index (NDVI) was used. The NDVI
was obtained from Landsat satellite images for the period 1987 to 2016.
1.5. Structure of the report
This report is organized in the following sections: Chapter 2 contains an abstract of the
most relevant results including its conclusions, followed by the background and
information sources described in Chapter 3. Chapter 4 presents the methodology used
and Chapter 5 the results obtained. Chapter 6 contains conclusions and remarks. In
Chapter 7 of this report the bibliography and appendices are presented.
2. SUMMARY AND CONCLUSIONS
A DEM-5m resolution analysis was used to delineate the watershed of the Silala River.
This watershed has an area of 95,53 km2 at the Inacaliri Police Station. In this
watershed, the surface hydrological processes occur as an integral system, with a
continuum of topographically-determined flow paths, and its boundaries are well
defined by the topography. The watershed of the Silala River has an important part of its
surface area in Bolivian territory. In this part of the watershed are located the headwater
streams or sources, including the “Cajones” and “Orientales” wetlands (bofedales).
The river network obtained digitally was consistent with the river network that appears
in the Chilean and Bolivian official cartographies and through the overlain historical
aerial photographs. Additionally, the longitudinal profile and the slopes were calculated
from the DEM-5m and it was shown that both perennial water sources of the Silala
fluvial system, “Cajones” and “Orientales”, flow from Bolivia to Chile. The lowest
elevation of the wetlands is 4323 m.a.s.l. and the river elevation at the border is
approximately 4277 m.a.s.l.
Using the watershed definitions and the river network extracted from the DEM-5m it
was possible to demonstrate clearly and in a simple way that the Silala and its
tributaries, as a whole, define an integral river system, from their sources in Bolivia to
Chile, therefore this means that it is a transnational watercourse.
The NDVI analyses over 29 years (1987 - 2016) showed that the wetlands’ surfaces
(Cajones and Orientales located in Bolivia) did not show any significant long-term
change. However, the wetland vegetation dynamics vary seasonally, particularly during
the rainy season (January –March), and there is also significant inter-annual variability.
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6 3.BACKGROUND AND INFORMATION SOURCESIn order to delineate the Silala watershed, the fundamental data correspond to the relief of the terrain. Initially, two information sources were available: i) The Global Digital Elevation Model, GDEM V2 (Tachikawa et al., 2011) from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) at 30 m resolution provided by The Ministry of Economy, Trade, and Industry (METI) of Japan and the United States National Aeronautics and Space Administration (NASA) called DEM-30m; and ii) a Digital Elevation Model DEM-15m resolution elaborated by and received from DIFROL. Figure 2 shows the watershed delineation using DEM-30m and DEM-15m. Figure 2. Delineation of the Silala River watershed at Inacaliri. The pink polygon and the green polygon correspond to the watershed delineation using the DEM-15m resolution and the DEM-30m, respectively. 12
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From Figure 2, it is clear that there are two areas where the borders do not match;
therefore it was necessary to use another DEM. Due to the nature of this project, the
new DEM should meet two characteristics; it should have a high resolution, and the
information should preferably not come from Chilean or Bolivian sources (i.e., the
information should ideally come from a neutral source).
A DEM that fits these characteristics was acquired from the Advanced Land Observing
Satellite (ALOS) Word 3D Digital Terrain Model (AW3DTM, for more details please
see the product characteristics available here: http://aw3d.jp/en/). This DEM is built
using data acquired by the Advanced Land Observing Satellite “Daichi” (ALOS) of the
Japan Aerospace Exploration Agency (JAXA), and high-resolution satellite images. The
DEM has 5-m resolution and a low Root Mean Square Error (RMSE) for the vertical
values, with an error of less than 5m (Tadono, 2014; Takaku et al., 2016). The DEM-5m
resolution as acquired is presented in Figure 3, and Figure 4 presents a 3D topographic
map with contours, main channels and the location of the points of the most relevant
geographic features.
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8 Figure 3. Digital Elevation Model (DEM), 5 m resolution purchased from the Japanese enterprise NTT data Co. 14
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Figure 4. Three dimensional representation of the relief from DEM-30m (top) and DEM-5m
(bottom).
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10 Other relevant sources of information include: a)Cartography from both the Chilean Military Geographical Institute (“ChileanIGM”) and the Bolivian Military Geographical Institute (“Bolivian IGM”), scale1:50.000.Three Chilean IGM maps, provided by DIFROL, these are: Inacaliri (IGM code 5-04-02-044-00).Cerro Inacaliri o del Cajón (IGM code 5-04-02-035-00).Línzor (IGM code 5-04-02-045-00).The Bolivian IGM maps were downloaded from the Bolivian IGM web page (http://www.igmbolivia.gob.bo/). These correspond to the following IGM maps: Cerro Silala Chico (code 5927-I H731 edition 1-IGM).Cerro Inacaliri (code 5928-II H731 edition 1-IGM).Volcán Chico (code 6027-IV H731 edition 1-IGM).Laguna Khara (code 6028-III H731 edition 1-IGM).b)Aerial photography and satellite images provided by the Chilean National Air Force(“Fuerza Aérea de Chile, Estado Mayor General”), through its PhotogrammetricService “Servicio Aerofotogramétrico-SAF”, and by DIFROL. These data setscorrespond to:Photo set flight Hycon 1:70.000, year 1956.Photo set AEROSERVICE 1:70.000, year 1961.Photo set SAF-GEOTEC 1:50.000, year 1997.Satellite image from the Chilean satellite Fasat-Charlie, year 2016.c)The Landsat satellite images to obtain the Normalized Difference Vegetation Index(NDVI) were downloaded from the USGS website https://earthexplorer.usgs.gov/Period 1987 – 1999 - Mission Landsat 5.Period 2002 – 2010 - Mission Landsat.Period 2014 – 2016 - Mission Landsat 8.4.METHODOLOGYFor a correct delineation of the river watershed, it is essential to identify the surface flow patterns (the paths of the overland flow and streams flow). To achieve this, we use 16
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standardized tools, approved by the professional and scientific community in the water
resources field and specifically in the hydrology field.
There are several algorithms to establish flow direction that have been validated and
published in the specialized scientific literature (Marthews et al., 2015). These
algorithms can be aggregated into the following two groups: the non-dispersive or
Single Flow Directions (SFD) algorithms, also the oldest, and the Multiple Flow
Direction (MFD) algorithms. While the MFD algorithms show improvements in the
routing flow for hydrological modelling, SFD algorithms (e.g. D8, Rho8, Orlandini’s
method known as D8-LTD, among others) are more robust and therefore more widely
used for the watershed delineation and establishing surface runoff patterns (Orlandini et
al., 2014). In particular, the D8 algorithm is programmed into the widely used
commercial software, ArcGIS by the Environmental Systems Research Institute, Inc.
(ESRI), within the spatial analysis tool called “hydrology”.
Once the flow directions are defined from a “hydrologically correct” DEM in the terms
explained by Thomas et al. (2017), the watershed can be delineated and the river
network can be extracted. Then, the accumulation of upstream area can be identified in
order to define the initiation of the natural channel network. This network is compared
against the IGM maps and aerial photography.
Another hydrological variable to be obtained is the Compound Topographic Index
(CTI). CTI is used to quantify the potential for channel formation, also known as the
ephemeral gullying potential. This hydrological variable was introduced in the early
1980s by the Agricultural Research Service of the United States Department of
Agriculture, USDA-ARS (Parker et al., 2010) and it is a fundamental parameter for
some hydrological models, for example the TOPMODEL (Beven, 1997; 2012).
The CTI is computed as follows:
(1)
where α is the drainage area upstream of the analyzed point, and β corresponds to the
local slope (gradient).
The CTI also can be used to verify if the results for the river network extracted from the
DEM correspond well with the channels observed from the satellite image. The above is
possible considering that the highest values of the CTI allow for the identification of the
gully channel initiation location (Momm et al., 2013). This evidence will show whether
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12 presently observed channels come from natural processes (e.g. water erosion) rather than artificial channelization. The study of the evolution of the highland Andean wetlands, locally called bofedales, is carried out by means of a spatial analysis of the surface extension cover by these wetlands, using the Normalized Difference Vegetation Index (NDVI). The NDVI is obtained from satellite images of the Landsat sensor missions 5, 7 and 8. The NDVI values and their spatial extension are analyzed for the period 1987 to 2016. 5.RESULTS5.1. Watershed delineation and drainage network extraction For the watershed delineation, an algorithm proposed by Jenson and Domingue (1988) was used. This algorithm is commonly known as the eight direction (D8) flow model and is incorporated into the hydrological module in the Tool Box of the ArcGIS 10 software. In general, DEMs under 10-m resolution obtained from remote sensing techniques present sink (or pit) depressions, which can be considered errors (Mark, 1988). These sinks are commonly present in high resolution DEMs (Zhu et al., 2013, Thomas et al., 2017). Additionally, as the cell size increases, the number of sinks in a dataset also often increases. For the raw DEM 5-m data, sinks were identified and digitally amended, using the hydrology module in Arctool box of ArcGis following standardized methodology (see Maidment, 2002; Johnson, 2009 and ESRI, 2016), in order to create an accurate representation of flow direction, based on accumulated flow. Typically, a filled DEM is called a “depressionless DEM” or “hydrologically correct DEM”. It is important to note that the sink areas of the raw DEM were spatially isolated (not connected), meaning that the filled sink did not affect the natural course of the flow surface. The flow directions for the hydrologically correct DEM are presented in Figure 5.A description of the filled sinks is presented in Appendix A.18
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Figure 5. Flow directions from DEM-5m resolution according the coding used in ArcGIS
software.
Subsequently, by means of the flow accumulation algorithm (also included in the
hydrologic module of ArcGIS Tool box), a GIS-layer was obtained. In this flow
accumulation layer, each cell corresponds to the sum of the number of cells contributing
from upstream. This procedure was done in order to identify the main channels. Figure
6 shows the accumulation for all cells of the DEM, and hence the topographic
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14 concentration.1 To allow the delineation of a watershed, an outlet point must be selected; this point should be located in the stream channel obtained from the flow accumulation algorithm. The outlet point for the watershed is located just downstream of the Inacaliri Police Station in the area called Inacaliri, at 4.9 km downstream of the Chile-Bolivia border, with UTM coordinates 596,453 E; 7,563,039 N (datum WGS84-19S). In Figure 6 are also represented the more relevant mountains and volcanoes, together with the maximum elevation of these points. Figure 6. Resulting GIS-layer from flow accumulation algorithms (D8) in ArcGIS software for the DEM-5m resolution. The lower left corner shows a zoom of the wetland areas and the international border. 1 The network thus identified represents potential flow paths; only a small subset of the major channels consists of perennially flowing channels. 20
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The delineation of the watershed at this point resulted in a drainage area of 95,535,125
(m2), i.e. 95.5 (km2). Of this area, 72.25% is in Bolivian territory and 27.75% is in
Chilean territory. Figure 6 also shows the limit of the Silala River watershed at Inacaliri,
the natural channel network (extracted using the flow accumulation algorithm) and the
reclassification of this network, using different thresholds of accumulated areas (defined
by the number of cells contributing to a particular location).
For comparison, Figure 7 shows the two coarser resolution polygons for the river
watershed (also included in Figure 2 of this report). Figure 7 shows that no significant
differences exist between the delineation of the watershed using the DEM-15m and the
DEM-5m, however the delineation with DEM-5m is more accurate in the flat areas and
allows for a better interpretation of the river network. Figure 7 shows the
topographically-defined channel network for the Silala watershed only, and also
illustrates the effect of using a different cell accumulation criterion to define the
existence of a channel (>20,000 cells, equivalent to >0.5 km2). The resulting network is
less dense (in comparison with Fig. 6), but is still more dense than the observed
network of flowing channels, and hence the criterion of the number of cells accumulated
is optimized below in order to better represent the known occurrence of perennial and
ephemeral channels in the watershed (see section 5.2 and 5.3).
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16 Figure 7. Watershed delineation for the Silala River at the Inacaliri Police Station from DEM-5m, also showing the watershed delineations from DEM-15m and DEM-30m. 5.2. Comparison between the channel network extracted from GIS methods and the Chilean and Bolivian official cartography Both Chilean IGM and Bolivian IGM cartography data sets were georeferenced, because these maps were in formats (paper scanned and portable document format, pdf) not compatible with GIS. The original sources of the Chilean IGM and Bolivian IGM cartography were projected onto the Universal Transverse Mercator (UTM) zone 19 south, but the reference datums are different. For Chile, the reference datum system 22
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corresponds to the SIRGAS-WGS84 (http://georepository.com/crs_5361/SIRGASChile-
UTM-zone-19S.html); and for Bolivia it is referred to the Provisional South
American Datum 1956 - PSAD56 (http://georepository.com/datum_6248/Provisional-
South-American-Datum-1956.html).
Consequently, the Bolivian IGM maps were projected onto WGS84-19S, using the
Tool-box from ArcGIS software (form PSAD56-19S to WGS84-19S). The WGS84
datum is widely used and internationally agreed (Sample and Loup, 2010; Uren and
Price, 2010), in particular for Global Positioning System (GPS) devices.
Subsequently, two mosaics were made with both data sources (see Section 3 a) in this
report). The Chilean IGM mosaic is presented in Figure 8 and compares the main
watercourses of the watershed (in light blue) against the drainage channel network
extracted from the DEM (in purple). This figure shows clearly that the extracted channel
network fits quite well with the channel network from the Chilean cartography.
Figure 8. Comparison between the Chilean IGM cartography (streams in cyan) and river
network (in purple) extracted from DEM-5.
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18 For the Bolivian IGM cartography, a mosaic was also built (with the IGM maps indicated in this report Chapter 3, Section a) and the result of the overlay with the channel network extracted was the same as that previously described for the Chilean case. This is shown in Figure 9, where the purple lines correspond to the channel network extracted digitally, and the cyan lines are rivers and streams defined in the IGM cartography of Bolivia. This goodness of fit is also verified for smaller channels, such as the Quebrada Silala (name according to toponymy of the Bolivian map), which are not always actively flowing. Figure 9. Comparison between the Bolivian IGM cartography (streams in cyan) and river network (in purple) extracted from DEM-5m. 24
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From Figures 6, 8 and 9 it is possible to note that for contributing cells greater than
500,000 in number (i.e. >12.5 km2), the Silala River (from both the Cajones and
Orientales wetlands to downstream) is well represented using the DEM-5m. This is
shown by comparing the purple lines for the streams extracted from the DEM-5m, the
light blue solid lines for the Chilean IGM and cyan solid lines for the Bolivian IGM (see
Figures 8 and 9). For a number of the cells contributing between 100,000 - 200,000 (i.e.
2.5 – 5.0 km2) tributary streams are also well represented using the DEM-5m. It is
shown by light purple lines for the streams extracted from the DEM-5m, light blue solid
lines for the Chilean IGM and cyan dashed lines for the Bolivian IGM (see Figures 8
and 9). In this latter case, the Quebrada Negra and Quebrada Inacaliri in Chile, and the
Quebrada Silala in Bolivia are clearly identified. Figure 10 shows the watershed
boundary and the river network (extracted from the DEM-5m). This river network was
classified into perennial and ephemeral streams according to the Bolivian and Chilean
IGM’s legend.
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20 Figure 10. Watershed of the Silala River at Inacaliri Police Station and channel network classified as perennial and ephemeral according to the Chilean IGM and the Bolivian IGM. 5.3. Comparison between the river networks extracted from GIS methods and aerial photographs Another means used for the comparison and verification of the channel network extracted from the DEM is a set of aerial photographs from the years 1954, 1961 and 1997. These photographs do not include the entire area of the watershed, but do include a large part of its channel network. The channel network shown in Figures 11 to 13 corresponds with those generated by a flow accumulation area greater than 150,000 26
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cells (> 3.75 km2). This criterion was established considering that the best fit between
the generated channel network and the IGM (Chile and Bolivia) cartography occurred
for the values of area accumulation in the range of 100,000 and 200,000 cells;
considering both the Silala River and its tributaries. The streams were classified as
either perennial or ephemeral, as shown in the legends of Figures 11 to 13, based on
both Chilean IGM and Bolivian IGM maps; only the main stream of the Silala fluvial
system (from Bolivia wetland sources, Cajones and Orientales, to downstream) is
recognized as a perennial water course in the IGM maps.
From Figure 11 (photo for the year 1954) it is possible to see that the Silala River,
Quebrada Negra and Quebrada Inacaliri are generally well represented. This image
presents mainly the Chilean territory. A more extended area is shown in Figure 12
(image for the year 1961), including the Chilean territory, and a large part of the
Bolivian territory. From Figure 12, it is possible also to verify that the river network
extracted from DEM agrees with the river channels that appear in this photo. Finally, for
the photo of the year 1997, the same result was found.
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22 Figure 11. Cropped aerial photography N° 5404, flight Hycon May 1954, scale 1:70.000. 28
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Figure 12. Cropped aerial photograph N°34-3191, flight Aero Service April 1961, Line 14-D,
scale 1:70.000.
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24 Figure 13. Cropped aerial photography N°008194, flight SAF-GEOTEC 1997, scale 1:50.000, S 23 Calama L37. Given that the extracted river network from DEM-5m is consistent with the river network in the IGM cartography and aerial photographs, a longitudinal profile of the Silala River was built from the DEM-5m and the river flow (the path of the rivers) calculated with the flow direction algorithm. This profile is presented in Figure 14 and its longitudinal slopes were compared with another profile built by Chile during joint fieldwork by Chilean and Bolivian technicians in October 2000. From Figure 14 it is possible to note that the profile of the Silala presents a nick-point at a distance of 7000 m from the Inacaliri Police Station (see Fig. 14) that divides the profile into two reaches (from the water source Orientales to the nick-point and from the nick-point to the Inacaliri Police Station). From the DEM-5m, the lowest elevation of the Bolivian wetlands is 4323 m.a.s.l and the elevation at the border is 4282 m.a.s.l. This latter figure 30
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compares well with the ground-based measurements made in 2000, which give a figure
of 4277 m.a.s.l. Given the 5m resolution of the DEM and the 5m Root Mean Square
error of the product, this is very satisfactory agreement.
Finally, three slopes were calculated for this comparison, the two reaches previously
mentioned and the slope from the other water source Cajones to the main channel.
These are shown in Table 1.
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26 Figure 14. Longitudinal profile of the Silala River and main tributaries, extracted from the DEM-5m. 32
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Based on
Slopes
Water source
Orientales
Silala downstream
Orientales
Water source
Cajones
DEM-5m 1.3% 5.0% 8.1%
Chilean and Bolivian
technicians 1.4% 4.3% 8.6%
Table 1. Average slopes comparison for the Silala longitudinal profile using two information
sources.
It is clear that both sources of information give slopes that are similar and that the
profiles show that the river flows from both water sources Orientales and Cajones (in
Bolivia) to Inacaliri (in Chile).
5.4. The Compound Topographic Index
The Compound Topographic Index (CTI) is also called the Topographic Wetness Index
(TWI; Wilson and Gallant, 2000) or simply the topographic index. This index has been
applied in numerous hydrological studies and applications for water flow path
estimation and moisture redistribution (Beven et al., 1995). According to Marthews et
al. (2015) the CTI represents “a measure of the relative propensity for the soil to, at a
point, become saturated to the surface, given the area that drains into it α and its local
slope β”. Conceptually, the increase of the drainage area α increases the accumulation of
the surface water (Beven, 2012), and the increase of the local slope β reduces it by the
increase of the gravitational outflow (Quinn et al., 1991).
The CTI was calculated from equation 1. For the variable α, upland drainage area, the
same flow direction GIS-layer was used (the deterministic eight node –D8). This
algorithm is used in global hydrological products such as HydroSHEDS (Lehner et al.,
2008; Lehner, 2013; http://www.hydrosheds.org/) and for various well-known GISbased
hydrological models, for example the Soil and Water Assessment Tool (SWAT;
Neitsch et al., 2005).
The local slope β was calculated for each cell using the Arctool box in the ArcGIS
software. This algorithm uses the largest height difference between the cell under
analysis and its eight neighbors (Burrough and McDonnell, 1998), and this value is
divided by the distance between the centers of these two cells. The result for CTI is
shown in Figure 15, overlapped with a satellite image for the year 2012 from the Fasat-
Annex I
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28 Charlie satellite. This Figure shows also two zoomed images, one for the Silala River and Quebrada Negra confluence and the other one for the wetland area. The values of CTI were classified into the range [13 – 19], in order to better represent the cells that have high values. The highest CTI values are more probably associated with the highest surface moisture (Marthews et al., 2015). Figure 15 shows that the high values of CTI are coincident with the river’s path, also demonstrating that there is a natural potential for soil water saturation in this area. 34
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Figure 15. CTI values for Silala River watershed.
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30 5.5. Analysis of the evolution of the spatial extent of the Silala highland Andean wetlands Landsat images (108 in total) were used for the determination of the surface extent over time of the two wetland areas, Cajones and Orientales (located in Bolivian territory), using the Normalized Difference Vegetation Index (NDVI). NDVI was first used in 1973 by Rouse et al. (1973) and this is one of the most widely used vegetation indexes with which to build vegetation maps. The NDVI is correlated with the biophysical properties of the vegetation, such as the density of the plant cover, green biomass, green leaf area index (LAI), percent green cover and the fraction of absorbed photosynthetically active radiation (Huete and Liu, 1994; Leprieur et al., 2000; Anyamba and Tucker, 2005; Jianga et al., 2006). Theoretically, NDVI values are represented as a ratio ranging in value from -1 to 1. According to Weier and Herring (2000), negative values of NDVI (values approaching -1) correspond to deep water. Values close to zero (-0.1 to 0.1) generally correspond to barren areas of rock, sand, or snow. Low, positive values represent shrub and grassland (approximately 0.2 to 0.4), while high values indicate temperate and tropical rainforests (values over 0.6 represent dense green vegetation). In a recent investigation carried out by White et al., (2016) on the arid region in Australia for NDVI-based wetland delineation it was found that an increase of NDVI with increasing vegetation cover was evident at all study sites, despite the differences in ranges of NDVI and on-ground vegetation cover. White et al., (2016) also concludes that “The increase in NDVI with vegetation cover also corresponds with differences in vegetation community composition: perennial vegetation has high NDVI; ephemeral spring tail vegetation exhibits a wider range of moderate NDVI; and surrounding dryland vegetation generally shows much lower NDVI”. For the Cajones and Orientales wetlands a classification based on NDVI values was done, grouping values into different ranges. In the Figures of Appendix B, the values of NDVI in the range -1.0 to 0.1 were not considered, as the NDVI values in this range corresponded to non-vegetated areas. It was considered that for NDVI values greater than 0.1 there was the presence of vegetation (as previously indicated). From the NDVI value 0.1 and increasing by 0.1, ranges of NDVI were created to analyze the spatial and temporal evolution of this index and consequently of the wetlands area. A summary of the results is shown in Table 2, and in Appendix B and Appendix C all the images analyzed are presented, and the areas according to the different NDVI ranges. Figure 16 shows the wetland surface areas (Cajones and Orientales) for all the Landsat images analyzed, considering only NDVI values greater than 0.1. The plot was divided into two classes, rainy season (January – March) and dry season (April – December). 36
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Although there are information gaps in the time series, it is possible to observe that
during the rainy season the wetland surface area has a greater range of variation (also
shown later in Fig. 17 and Table 2). It is not possible to verify if this time series is truly
stationary, however from a visual inspection of Figure 16, there is no obvious tendency
to decrease or increase, therefore, it is suggested that the dynamic of the wetland has
been maintained essentially unchanged since 1987.
Figure 16. Surface time series for Cajones and Orientales vegetated area from Landsat
imagery, based on NDVI values greater than 0.1.
Table 2 shows that for the months January to March the average extent of the wetland
surfaces is the largest. From April, the average surface decreases markedly until June.
This reduction of the surface area can be explained by the decrease of the precipitation
with the consequent decrease of the aquifer recharge and finally, a gradual decrease of
the water flow rate in the river. From June to November the base flow in the river
system conserves and maintains the wetlands with a minimal vegetation activity. From
December, the vegetation of the wetland expands again as a consequence of the onset of
the rainy season. This relation between the rainfall and wetlands surface is presented in
Figure 17. This graph shows the average monthly extent of the surface wetlands, using
the criterion of NDVI values greater than 0.1 for the 108 Landsat images analyzed, and
the average monthly rainfall for the Inacaliri meteorological station2 for the period 1987
– 2016. Additionally, in Figure 17 are the maximal and minimal surface values for the
time series images, in order to show the large range and values of the surface extent
during the rainfall season and the contrast with the small range and values during the
dry season.
2 See Muñoz et al., 2017 for location details.
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32 Surface (km2) per NDVI Values Range Month barren areas of rock/snow/sand 0.1 0.1 - 0.2 0.2 - 0.3 0.3 - 0.4 0.4 - 0.5 0.5 - 0.6 > 0.6 Total surface considering ranges [0.1 -1.0] January 0.752 0.102 0.057 0.020 0.011 0.003 0.001 0.194 February 0.775 0.088 0.051 0.021 0.008 0.002 0.000 0.171 March 0.767 0.082 0.060 0.024 0.009 0.004 0.001 0.179 April 0.871 0.061 0.013 0.001 0.000 0.000 0.000 0.075 May 0.887 0.053 0.006 0.000 0.000 0.000 0.000 0.059 June 0.931 0.015 0.000 0.000 0.000 0.000 0.000 0.015 July 0.925 0.021 0.000 0.000 0.000 0.000 0.000 0.021 August 0.928 0.018 0.000 0.000 0.000 0.000 0.000 0.018 September 0.928 0.018 0.000 0.000 0.000 0.000 0.000 0.018 October 0.928 0.017 0.001 0.000 0.000 0.000 0.000 0.018 November 0.921 0.020 0.004 0.000 0.000 0.000 0.000 0.025 December 0.916 0.022 0.007 0.001 0.000 0.000 0.000 0.030 Average 0.877 0.043 0.017 0.006 0.002 0.001 0.000 0.069 Maximum 0.931 0.102 0.060 0.024 0.011 0.004 0.001 0.194 Minimum 0.752 0.015 0.000 0.000 0.000 0.000 0.000 0.015 Table 2. Seasonal dynamic of the wetlands (Cajones and Orientales) as function of the monthly average NDVI (1987 – 2016 yrs.). 38
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Figure 17. Relation between average monthly rainfall and average surface extent of the
wetlands, for the period 1987 – 2016.
6. CONCLUSIONS AND REMARKS
The DEM 5-m resolution analysis has shown that the Silala fluvial system has an
exoreic watershed of 95,53 km2 at Inacaliri. In this watershed, the surface hydrological
processes occur as an integral system, a topographic continuum, and its boundaries are
well defined by the topography.
This watershed has an important part of its area in Bolivian territory, and in this part of
the watershed are located the headwater streams or sources, including the wetlands.
Headwater streams have a very important role in transporting sediments from hillslope
into downstream channel networks; providing diverse habitats and refuges for varied
aquatic and riparian organism; and supplying water to lower elevation in arid and
semiarid regions (Milliman and Syvitski, 1992; Meyer and Wallace, 2001; Gomi et al.,
2002).
The paths of both the overland flow and the streamflow for the Silala watershed were
obtained from the DEM and the channel network of the watershed was defined. This
channel network obtained digitally is consistent with the river network that appears in
the Chilean and Bolivian official cartographies. This watershed has a clearly defined
main channel (Silala River), but also has tributary streams that are part of the watershed
river network. Both the Silala main river channel and its tributary channels were
Annex I
39
34 verified through the overlay of the river network extracted from the DEM against aerial photographs. Additionally, the longitudinal profile and the slope calculation show that both the major water sources of the Silala fluvial system, i.e. the Cajones and Orientales wetlands, flow from Bolivia to Chile. Using the watershed definitions and the river network extracted from the DEM it is possible to demonstrate clearly that the Silala and its tributaries, as a whole, define an integral river system, from their sources in Bolivia to Chile, therefore this means that it is a transnational watercourse. The same results were obtained with the overlay of the river network with the photos and maps. When the Compound Topographic Index (CTI) was calculated and overlain on a satellite image this showed that there is coherence between the highest CTI values and wetter areas in the watershed. The NDVI analyses over 29 years (1987 - 2016) show that the wetlands’ surface extent (Cajones and Orientales located in Bolivia) remains substantially the same (see Appendix B, which provides a set of NDVI images). The wetland dynamics, as represented by the vegetation, are characterized by a strong inter-annual variability, but the global pattern shows no systematic change over the period of record. For the time period January to March, the vegetation had a more active behavior, as evidenced from the higher NDVI values (> 0.5), which coincide with the rainy season. A less active behavior of the vegetation was observed in the wetlands during the dry months –June to October- with NDVI between 0.10 – 0.29. This dynamic can be explained by the water availability, e.g. the amount of precipitation, with its subsequent effects on aquifer level and river discharge and also by the inherent seasonal cycle of the vegetation. Evidence of this same behavior was found by White et al., (2016) in a similar environment (Australian desert) to that of the Silala River system. 40
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7. REFERENCES
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36 Lehner, B., Verdin, K., Jarvis, A., 2008. New global hydrography derived from spaceborne elevation data. Eos, Transactions, AGU, 89(10), 93-94. Lehner, B., 2013. HydroSHEDS Technical Documentation. Conservation Science Program, World Wildlife Fund US, Washington, DC. http://www.hydrosheds.org/images/inpages/HydroSHEDS_TechDoc_v1_2.pdf. Leprieur, C., Kerr, Y.H., Mastorchio, S., and Meunier, J.C., 2000. Monitoring Vegetation Cover Across Semi-Arid Regions: Comparison of remote observations from various scales. International Journal of Remote Sensing, 21(2): 281–300. Mark, D. M., 1988. Network Models in Geomorphology. Modelling Geomorphological Systems, ed. M. G. Anderson. New York: John Wiley, 73–97. Marthews, T.R., Dadson, S.J., Lehener, B., Abele, S., and Gedney, N., 2015. High-Resolution Global Topographic Index Values for Use in Large-Scale Hydrological Modeling. Hydrol. Earth Syst. Sci., 19, 91-104. doi:10.5194/hess-19-91-2015 Maidment, D. R., ed., 2002. Arc Hydro: GIS for Water Resources, ESRI Press, Redlands, Ca. McGinnies, W.G., Goldman, B.J., and Paylore P. (Eds.). 1968. Deserts of the World: An Appraisal of Research into their Physical and Biological Environments. Tucson, University of Arizona Press. Meyer, J.L., Wallace, J.B., 2001. Lost Linkages and Lotic Ecology: Rediscovering Small Streams. In: Press, M., Huntly, N., Levin, S. (Eds.), Ecology: Achievement and Challenge. Blackwell Science, Oxford, UK, pp. 295–317. Milliman, J.D., Syvitski, J.P.M., 1992. Geomorphic/Tectonic Control of Sediment Discharge to the Ocean: The Importance of Small Mountainous Sivers. The Journal of Geology 100 (5), 525–544. Momm, H.G., Binger, R.L., Wells, R.R., Rigby, J.R. and Dabney, S.M. 2013. Effects of Topographic Characteristics on Compound Topographic Index for Identification of Gully Channel Initiation Location. Transaction of ASABE 56(2): 523-537. Muñoz J.F., Suárez F., Fernández B., Maass T., 2017. Hydrology of the Silala River Basin.(Vol. 5, Annex VII). Neitsch, S.L., Arnold, J.G., Kiniry, J.R. and Williams J.R. 2005. Soil and Water Assessment Tool. Theoretical Documentation. Version 2005, USDA-ARS, Temple, TX, USA, 494 p. Orlandini, S., Moretti, G., and Gavioli, A., 2014. Analytical Basis for Determining Slope Lines in Grid Digital Elevation Models. Water Resour. Res., 50, 529–539, doi:10.1002/2013WR014606. 42
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38 Wilson, J. P. and Gallant, J. C., 2000. Terrain Analysis Principles and Applications, John Wiley & Sons, New York, 2000. Weier J. and Herring D., 2000, Measuring Vegetation (NDVI & EVI), http://earthobservatory.nasa.gov/Features/MeasuringVegetation/ (last access: 22 December, 2016). White, D.C., Lewisa, M.M., Greenb, G. and Gotchc, T.B., 2016. A generalizable NDVI-Based Wetland Delineation Indicator for Remote Monitoring of Groundwater Flows in the Australian Great Artesian Basin, Ecological Indicators 60, 1309–1320. Zhu, D., Ren, Q,. Chen, Y. and Cluckie, I.D., 2013. An effective depression filling algorithm for DEM-based 2-D surface flow modeling. Hydrol. Earth Syst. Sci., 17, 495-505, Doi:10.5194/hess-17-495-2013. 44
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APPENDIX A
Information about the filled DEM procedure.
Total pixels filled in the overall DEM-5m was 6,974 of 5,307,766 (0.13%).
Total pixels filled for longitudinal profile of Silala and main tributaries was 119
of 2,330 (5.1%).
The following tables present the filled pixels for the case of the longitudinal
channel profile. Only 22 pixels were filled with more than one meter.
Figure A in this appendix shows the location of the filled pixels with the amount
(height) of meter filled.
Annex I Appendix A
45
40 Distance from Inacaliri Police Station (m) Elevation from original DEM (m) Elevation from original filled DEM (m) Filled (m) 39.14 4038 4039 1 44.14 4038 4039 1 49.14 4038 4039 1 172.78 4050 4051 1 590.77 4122 4123 1 825.12 4142 4144 2 830.12 4142 4144 2 835.12 4142 4144 2 932.19 4087 4088 1 947.90 4153 4154 1 954.97 4153 4154 1 962.04 4153 4154 1 969.12 4153 4154 1 1042.75 4159 4160 1 1047.75 4159 4160 1 1141.19 4106 4107 1 1146.19 4106 4107 1 1151.19 4106 4107 1 1156.19 4106 4107 1 1306.04 4118 4121 3 1313.11 4118 4121 3 1320.18 4118 4121 3 1374.68 4121 4122 1 1379.68 4121 4122 1 1384.68 4121 4122 1 1389.68 4121 4122 1 1464.03 4194 4195 1 1529.39 4198 4199 1 1533.68 4128 4129 1 1534.39 4198 4199 1 1539.39 4198 4199 1 1540.75 4128 4129 1 1547.82 4128 4129 1 1559.89 4128 4129 1 1588.53 4206 4207 1 1803.74 4218 4220 2 1808.74 4218 4220 2 1857.88 4219 4221 2 2129.31 4157 4158 1 46
Annex I Appendix A
41
Distance from Inacaliri Police
Station (m)
Elevation from original
DEM (m)
Elevation from original filled
DEM (m)
Filled
(m)
3299.80 4200 4202 2
3395.16 4214 4215 1
3402.23 4214 4215 1
3481.73 4206 4207 1
3488.80 4206 4207 1
3677.30 4215 4216 1
3684.37 4215 4216 1
3691.44 4215 4216 1
3729.73 4216 4217 1
3736.80 4216 4217 1
3874.73 4233 4235 2
3879.73 4233 4235 2
3963.37 4235 4236 1
4096.36 4234 4236 2
4103.43 4234 4236 2
4110.51 4234 4236 2
4267.79 4239 4240 1
4490.93 4249 4251 2
4495.93 4249 4251 2
4657.00 4261 4262 1
4662.00 4261 4262 1
4669.07 4261 4262 1
4688.21 4261 4262 1
4700.28 4261 4262 1
4705.28 4261 4262 1
5369.92 4290 4291 1
5427.35 4292 4293 1
5432.35 4292 4293 1
5515.99 4297 4298 1
5520.99 4297 4298 1
5525.99 4297 4298 1
5633.77 4303 4304 1
5659.98 4303 4304 1
6065.41 4327 4328 1
6113.69 4341 4342 1
6118.69 4341 4342 1
6150.76 4333 4334 1
6155.76 4333 4334 1
6156.98 4343 4344 1
Annex I Appendix A
47
42 Distance from Inacaliri Police Station (m) Elevation from original DEM (m) Elevation from original filled DEM (m) Filled (m) 6160.76 4333 4334 1 6165.76 4333 4334 1 6170.76 4333 4334 1 6321.83 4351 4356 5 6446.69 4355 4360 5 6453.76 4355 4360 5 6460.83 4355 4360 5 6467.90 4355 4360 5 7107.11 4408 4409 1 7235.76 4420 4422 2 7408.75 4383 4384 1 7734.18 4386 4387 1 7741.25 4386 4387 1 7748.32 4386 4387 1 7755.39 4386 4387 1 7762.46 4386 4387 1 7769.53 4386 4387 1 8168.39 4397 4398 1 8242.03 4398 4399 1 8249.10 4398 4399 1 8254.10 4398 4399 1 8289.10 4398 4399 1 8294.10 4398 4399 1 8391.53 4401 4402 1 8434.81 4402 4403 1 8466.88 4402 4403 1 8471.88 4402 4403 1 8476.88 4402 4403 1 8481.88 4402 4403 1 8775.02 4407 4408 1 8780.02 4407 4408 1 8785.02 4407 4408 1 8790.02 4407 4408 1 8795.02 4407 4408 1 8960.38 4408 4409 1 8965.38 4408 4409 1 8970.38 4408 4409 1 8975.38 4408 4409 1 8980.38 4408 4409 1 48
Annex I Appendix A
43
8985.38 4408 4409 1
8990.38 4408 4409 1
Annex I Appendix A
49
44 Figure A. Location of pixels filled and the amount (height) of meter filled 50
Annex I Appendix A
45
APPENDIX B
Landsat Images: Extent and distribution of wetland area, based on ranges between <0.1
and >0.6 NVDI thresholds.
The background image used only as reference is the same for all Figures. It corresponds
to a satellite image from Fasat-Charlie 2016.
Annex I Appendix B
51
46 52
Annex I Appendix B
47
Annex I Appendix B
53
48 54
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49
Annex I Appendix B
55
50 56
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51
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57
52 58
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54 60
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56 62
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58 64
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60 66
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67
62 68
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64 70
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66 72
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68 74
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70 76
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Annex I Appendix B
77
72 78
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Annex I Appendix B
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74 80
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APPENDIX C
Statistics NDVI
Image Date Surface (km2) per NDVI Values Range
Month Day Year <= 0.1 0.1 - 0.2 0.2 - 0.3 0.3 - 0.4 0.4 - 0.5 0.5 - 0.6 > 0.6 Total
January 31 1987 0.747 0.090 0.059 0.025 0.018 0.007 0.000 0.199
November 23 1987 0.930 0.013 0.004 0.000 0.000 0.000 0.000 0.016
January 2 1988 0.774 0.111 0.039 0.013 0.008 0.002 0.000 0.172
January 2 1989 0.732 0.143 0.043 0.019 0.006 0.003 0.000 0.214
January 29 1992 0.756 0.120 0.043 0.017 0.009 0.001 0.000 0.190
January 2 1994 0.756 0.123 0.042 0.015 0.007 0.002 0.000 0.190
January 18 1994 0.755 0.121 0.045 0.016 0.008 0.001 0.000 0.191
January 5 1995 0.884 0.039 0.015 0.008 0.000 0.000 0.000 0.062
March 26 1995 0.871 0.050 0.016 0.008 0.000 0.000 0.000 0.075
April 11 1995 0.891 0.039 0.013 0.004 0.000 0.000 0.000 0.055
May 29 1995 0.920 0.025 0.001 0.000 0.000 0.000 0.000 0.026
June 14 1995 0.926 0.019 0.001 0.000 0.000 0.000 0.000 0.020
July 16 1995 0.935 0.011 0.000 0.000 0.000 0.000 0.000 0.011
August 17 1995 0.935 0.011 0.000 0.000 0.000 0.000 0.000 0.011
September 2 1995 0.939 0.007 0.000 0.000 0.000 0.000 0.000 0.007
September 18 1995 0.920 0.026 0.000 0.000 0.000 0.000 0.000 0.026
October 4 1995 0.923 0.023 0.000 0.000 0.000 0.000 0.000 0.023
October 20 1995 0.923 0.022 0.001 0.000 0.000 0.000 0.000 0.023
February 9 1996 0.867 0.048 0.018 0.010 0.004 0.000 0.000 0.079
February 25 1996 0.874 0.048 0.014 0.008 0.002 0.000 0.000 0.072
April 13 1996 0.896 0.039 0.011 0.000 0.000 0.000 0.000 0.050
April 29 1996 0.925 0.020 0.001 0.000 0.000 0.000 0.000 0.021
May 31 1996 0.917 0.029 0.000 0.000 0.000 0.000 0.000 0.029
June 16 1996 0.927 0.019 0.000 0.000 0.000 0.000 0.000 0.019
July 2 1996 0.935 0.011 0.000 0.000 0.000 0.000 0.000 0.011
July 18 1996 0.935 0.011 0.000 0.000 0.000 0.000 0.000 0.011
August 3 1996 0.935 0.011 0.000 0.000 0.000 0.000 0.000 0.011
August 19 1996 0.935 0.011 0.000 0.000 0.000 0.000 0.000 0.011
September 4 1996 0.946 0.000 0.000 0.000 0.000 0.000 0.000 0.000
September 20 1996 0.935 0.011 0.000 0.000 0.000 0.000 0.000 0.011
October 6 1996 0.932 0.014 0.000 0.000 0.000 0.000 0.000 0.014
October 22 1996 0.928 0.018 0.000 0.000 0.000 0.000 0.000 0.018
December 9 1996 0.935 0.011 0.000 0.000 0.000 0.000 0.000 0.011
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76 May 2 1997 0.828 0.087 0.031 0.000 0.000 0.000 0.000 0.118 June 19 1997 0.930 0.016 0.000 0.000 0.000 0.000 0.000 0.016 August 6 1997 0.937 0.009 0.000 0.000 0.000 0.000 0.000 0.009 August 22 1997 0.932 0.014 0.000 0.000 0.000 0.000 0.000 0.014 September 7 1997 0.933 0.013 0.000 0.000 0.000 0.000 0.000 0.013 September 23 1997 0.924 0.020 0.002 0.000 0.000 0.000 0.000 0.022 October 9 1997 0.928 0.016 0.002 0.000 0.000 0.000 0.000 0.018 Image Date Surface (km2) per NDVI Values Range Month Day Year <= 0.1 0.1 - 0.2 0.2 - 0.3 0.3 - 0.4 0.4 - 0.5 0.5 - 0.6 > 0.6 Total October 25 1997 0.922 0.020 0.005 0.000 0.000 0.000 0.000 0.024 November 10 1997 0.918 0.020 0.007 0.001 0.000 0.000 0.000 0.028 December 12 1997 0.914 0.022 0.009 0.001 0.000 0.000 0.000 0.032 December 28 1997 0.903 0.029 0.010 0.005 0.000 0.000 0.000 0.043 February 14 1998 0.876 0.042 0.015 0.010 0.003 0.000 0.000 0.070 March 2 1998 0.768 0.078 0.064 0.023 0.010 0.004 0.000 0.178 March 2 1998 0.881 0.036 0.020 0.008 0.001 0.000 0.000 0.065 March 18 1998 0.757 0.094 0.063 0.019 0.012 0.002 0.000 0.189 June 6 1998 0.925 0.020 0.001 0.000 0.000 0.000 0.000 0.021 June 22 1998 0.930 0.016 0.000 0.000 0.000 0.000 0.000 0.016 July 8 1998 0.925 0.021 0.000 0.000 0.000 0.000 0.000 0.021 August 9 1998 0.931 0.015 0.000 0.000 0.000 0.000 0.000 0.015 September 10 1998 0.934 0.012 0.000 0.000 0.000 0.000 0.000 0.012 November 29 1998 0.906 0.029 0.010 0.001 0.000 0.000 0.000 0.040 December 31 1998 0.914 0.024 0.005 0.003 0.000 0.000 0.000 0.032 January 16 1999 0.766 0.114 0.043 0.014 0.008 0.001 0.000 0.180 February 1 1999 0.869 0.050 0.019 0.009 0.000 0.000 0.000 0.077 May 24 1999 0.919 0.025 0.002 0.000 0.000 0.000 0.000 0.027 June 9 1999 0.941 0.005 0.000 0.000 0.000 0.000 0.000 0.005 July 11 1999 0.937 0.009 0.000 0.000 0.000 0.000 0.000 0.009 June 25 1999 0.936 0.010 0.000 0.000 0.000 0.000 0.000 0.010 July 27 1999 0.937 0.009 0.000 0.000 0.000 0.000 0.000 0.009 August 12 1999 0.941 0.005 0.000 0.000 0.000 0.000 0.000 0.005 August 28 1999 0.941 0.005 0.000 0.000 0.000 0.000 0.000 0.005 September 13 1999 0.935 0.011 0.000 0.000 0.000 0.000 0.000 0.011 September 29 1999 0.935 0.011 0.000 0.000 0.000 0.000 0.000 0.011 November 16 1999 0.917 0.022 0.007 0.000 0.000 0.000 0.000 0.029 December 2 1999 0.914 0.023 0.009 0.001 0.000 0.000 0.000 0.032 December 18 1999 0.903 0.030 0.013 0.001 0.000 0.000 0.000 0.043 November 10 2000 0.946 0.000 0.000 0.000 0.000 0.000 0.000 0.000 82
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January 8 2002 0.746 0.113 0.060 0.019 0.007 0.000 0.000 0.200
January 24 2002 0.737 0.118 0.067 0.016 0.008 0.000 0.000 0.209
February 15 2004 0.729 0.085 0.082 0.034 0.012 0.005 0.000 0.217
March 5 2005 0.774 0.107 0.046 0.014 0.005 0.000 0.000 0.172
March 20 2005 0.731 0.131 0.057 0.021 0.006 0.000 0.000 0.215
March 7 2006 0.756 0.101 0.055 0.023 0.009 0.002 0.000 0.190
January 22 2007 0.707 0.133 0.071 0.022 0.012 0.001 0.000 0.239
February 7 2007 0.710 0.147 0.061 0.022 0.006 0.000 0.000 0.236
February 23 2007 0.741 0.104 0.064 0.028 0.007 0.001 0.000 0.204
February 10 2008 0.713 0.149 0.054 0.020 0.007 0.003 0.000 0.233
Image Date Surface (km2) per NDVI Values Range
Month Day Year <= 0.1 0.1 - 0.2 0.2 - 0.3 0.3 - 0.4 0.4 - 0.5 0.5 - 0.6 > 0.6 Total
March 13 2008 0.732 0.111 0.070 0.023 0.008 0.002 0.000 0.214
March 16 2009 0.719 0.106 0.072 0.035 0.011 0.003 0.000 0.227
January 14 2010 0.662 0.147 0.090 0.032 0.014 0.002 0.000 0.284
February 15 2010 0.664 0.131 0.097 0.032 0.019 0.003 0.000 0.282
March 19 2010 0.662 0.158 0.086 0.030 0.011 0.001 0.000 0.284
October 13 2010 0.939 0.007 0.000 0.000 0.000 0.000 0.000 0.007
November 14 2010 0.922 0.023 0.001 0.000 0.000 0.000 0.000 0.024
January 1 2011 0.885 0.041 0.017 0.003 0.000 0.000 0.000 0.061
April 23 2011 0.879 0.045 0.019 0.003 0.000 0.000 0.000 0.067
May 25 2011 0.913 0.032 0.001 0.000 0.000 0.000 0.000 0.033
August 29 2011 0.941 0.005 0.000 0.000 0.000 0.000 0.000 0.005
November 1 2011 0.921 0.025 0.000 0.000 0.000 0.000 0.000 0.025
April 12 2013 0.809 0.115 0.022 0.000 0.000 0.000 0.000 0.137
April 28 2013 0.826 0.109 0.011 0.000 0.000 0.000 0.000 0.120
May 14 2013 0.847 0.095 0.005 0.000 0.000 0.000 0.000 0.099
May 30 2013 0.868 0.075 0.004 0.000 0.000 0.000 0.000 0.078
June 15 2013 0.946 0.000 0.000 0.000 0.000 0.000 0.000 0.000
July 1 2013 0.905 0.041 0.000 0.000 0.000 0.000 0.000 0.041
July 17 2013 0.889 0.057 0.000 0.000 0.000 0.000 0.000 0.057
August 2 2013 0.889 0.057 0.000 0.000 0.000 0.000 0.000 0.057
August 18 2013 0.889 0.055 0.002 0.000 0.000 0.000 0.000 0.057
September 19 2013 0.896 0.049 0.001 0.000 0.000 0.000 0.000 0.050
January 9 2014 0.705 0.052 0.097 0.042 0.026 0.017 0.006 0.241
February 26 2014 0.704 0.081 0.085 0.040 0.023 0.011 0.004 0.242
March 13 2014 0.740 0.049 0.086 0.041 0.017 0.012 0.002 0.206
January 28 2015 0.705 0.086 0.085 0.033 0.023 0.009 0.005 0.241
March 1 2015 0.724 0.042 0.103 0.040 0.019 0.013 0.006 0.222
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78 September 17 2015 0.946 0.000 0.000 0.000 0.000 0.000 0.000 0.000 November 4 2015 0.936 0.010 0.000 0.000 0.000 0.000 0.000 0.010 December 6 2015 0.930 0.015 0.001 0.000 0.000 0.000 0.000 0.016 January 16 2016 0.721 0.084 0.088 0.033 0.014 0.006 0.000 0.225 March 3 2016 0.728 0.045 0.088 0.044 0.023 0.013 0.005 0.218 March 11 2016 0.895 0.036 0.014 0.002 0.000 0.000 0.000 0.083 Average 0.863 0.048 0.022 0.008 0.003 0.001 0.000 0.083 Maximum 0.946 0.158 0.103 0.044 0.026 0.017 0.006 0.284 Minimum 0.662 0.000 0.000 0.000 0.000 0.000 0.000 0.000 Image Date Surface (km2) per NDVI Values Range Month Day Year <= 0.1 0.1 - 0.2 0.2 - 0.3 0.3- 0.4 0.4 - 0.5 0.5 - 0.6 > 0.6 Total January 31 1987 0.747 0.090 0.059 0.025 0.018 0.007 0.000 0.199 January 2 1988 0.774 0.111 0.039 0.013 0.008 0.002 0.000 0.172 January 2 1989 0.7317 0.143 0.043 0.019 0.006 0.003 0.000 0.214 January 29 1992 0.756 0.120 0.043 0.017 0.009 0.001 0.000 0.190 January 2 1994 0.756 0.123 0.042 0.015 0.007 0.002 0.000 0.190 January 18 1994 0.7551 0.121 0.045 0.016 0.008 0.001 0.000 0.191 January 5 1995 0.8838 0.039 0.015 0.008 0.000 0.000 0.000 0.062 January 16 1999 0.7659 0.114 0.043 0.014 0.008 0.001 0.000 0.180 January 8 2002 0.7461 0.113 0.060 0.019 0.007 0.000 0.000 0.200 January 24 2002 0.7371 0.118 0.067 0.016 0.008 0.000 0.000 0.209 January 22 2007 0.7074 0.133 0.071 0.022 0.012 0.001 0.000 0.239 January 14 2010 0.6615 0.147 0.090 0.032 0.014 0.002 0.000 0.284 January 1 2011 0.8847 0.041 0.017 0.003 0.000 0.000 0.000 0.061 January 9 2014 0.7047 0.052 0.097 0.042 0.026 0.017 0.006 0.241 January 28 2015 0.7047 0.086 0.085 0.033 0.023 0.009 0.005 0.241 January 16 2016 0.7209 0.084 0.088 0.033 0.014 0.006 0.000 0.225 Average 0.752 0.102 0.057 0.020 0.011 0.003 0.001 0.194 Maximum 0.885 0.147 0.097 0.042 0.026 0.017 0.006 0.336 Minimum 0.662 0.039 0.015 0.003 0.000 0.000 0.000 0.057 84
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Image Date Surface (km2) per NDVI Values Range
Month Day Year <= 0.1 0.1 - 0.2 0.2 - 0.3 0.3- 0.4 0.4 - 0.5 0.5 - 0.6 > 0.6 Total
February 9 1996 0.8667 0.048 0.018 0.010 0.004 0.000 0.000 0.079
February 25 1996 0.8739 0.048 0.014 0.008 0.002 0.000 0.000 0.072
February 14 1998 0.8757 0.042 0.015 0.010 0.003 0.000 0.000 0.070
February 1 1999 0.8685 0.050 0.019 0.009 0.000 0.000 0.000 0.077
February 15 2004 0.729 0.085 0.082 0.034 0.012 0.005 0.000 0.217
February 7 2007 0.7101 0.147 0.061 0.022 0.006 0.000 0.000 0.236
February 23 2007 0.7407 0.104 0.064 0.028 0.007 0.001 0.000 0.204
February 10 2008 0.7128 0.149 0.054 0.020 0.007 0.003 0.000 0.233
February 15 2010 0.6642 0.131 0.097 0.032 0.019 0.003 0.000 0.282
February 26 2014 0.7038 0.081 0.085 0.040 0.023 0.011 0.004 0.242
Average 0.775 0.088 0.051 0.021 0.008 0.002 0.000 0.171
Maximum 0.876 0.149 0.097 0.040 0.023 0.011 0.004 0.282
Minimum 0.664 0.042 0.014 0.008 0.000 0.000 0.000 0.070
Image Date Surface (km2) per NDVI Values Range
Month Day Year <= 0.1 0.1 - 0.2 0.2 - 0.3 0.3- 0.4 0.4 - 0.5 0.5 - 0.6 > 0.6 Total
March 26 1995 0.8712 0.050 0.016 0.008 0.000 0.000 0.000 0.075
March 2 1998 0.7677 0.078 0.064 0.023 0.010 0.004 0.000 0.178
March 2 1998 0.8811 0.036 0.020 0.008 0.001 0.000 0.000 0.065
March 18 1998 0.7569 0.094 0.063 0.019 0.012 0.002 0.000 0.189
March 5 2005 0.774 0.107 0.046 0.014 0.005 0.000 0.000 0.172
March 20 2005 0.7308 0.131 0.057 0.021 0.006 0.000 0.000 0.215
March 7 2006 0.756 0.101 0.055 0.023 0.009 0.002 0.000 0.190
March 13 2008 0.7317 0.111 0.070 0.023 0.008 0.002 0.000 0.214
March 16 2009 0.7191 0.106 0.072 0.035 0.011 0.003 0.000 0.227
March 19 2010 0.6615 0.158 0.086 0.030 0.011 0.001 0.000 0.284
March 13 2014 0.7398 0.049 0.086 0.041 0.017 0.012 0.002 0.206
March 1 2015 0.7236 0.042 0.103 0.040 0.019 0.013 0.006 0.222
March 3 2016 0.7281 0.045 0.088 0.044 0.023 0.013 0.005 0.218
March 11 2016 0.8946 0.036 0.014 0.002 0.000 0.000 0.000 0.051
Average 0.767 0.082 0.060 0.024 0.009 0.004 0.001 0.179
Maximum 0.895 0.158 0.103 0.044 0.023 0.013 0.006 0.284
Minimum 0.662 0.036 0.014 0.002 0.000 0.000 0.000 0.051
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80 Image Date Surface (km2) per NDVI Values Range Month Day Year <= 0.1 0.1 - 0.2 0.2 - 0.3 0.3- 0.4 0.4 - 0.5 0.5 - 0.6 > 0.6 Total April 11 1995 0.891 0.039 0.013 0.004 0.000 0.000 0.000 0.016 April 13 1996 0.8964 0.039 0.011 0.000 0.000 0.000 0.000 0.011 April 29 1996 0.9252 0.020 0.001 0.000 0.000 0.000 0.000 0.001 April 23 2011 0.8793 0.045 0.019 0.003 0.000 0.000 0.000 0.022 April 12 2013 0.8091 0.115 0.022 0.000 0.000 0.000 0.000 0.022 April 28 2013 0.8262 0.109 0.011 0.000 0.000 0.000 0.000 0.011 Average 0.871 0.061 0.013 0.001 0.000 0.000 0.000 0.014 Maximum 0.925 0.115 0.022 0.004 0.000 0.000 0.000 0.022 Minimum 0.809 0.020 0.001 0.000 0.000 0.000 0.000 0.001 Image Date Surface (km2) per NDVI Values Range Month Day Year <= 0.1 0.1 - 0.2 0.2 - 0.3 0.3- 0.4 0.4 - 0.5 0.5 - 0.6 > 0.6 Total May 29 1995 0.9198 0.025 0.001 0.000 0.000 0.000 0.000 0.026 May 31 1996 0.9171 0.029 0.000 0.000 0.000 0.000 0.000 0.029 May 2 1997 0.828 0.087 0.031 0.000 0.000 0.000 0.000 0.118 May 24 1999 0.9189 0.025 0.002 0.000 0.000 0.000 0.000 0.027 May 25 2011 0.9126 0.032 0.001 0.000 0.000 0.000 0.000 0.033 May 14 2013 0.8469 0.095 0.005 0.000 0.000 0.000 0.000 0.099 May 30 2013 0.8676 0.075 0.004 0.000 0.000 0.000 0.000 0.078 Average 0.887 0.053 0.006 0.000 0.000 0.000 0.000 0.059 Maximum 0.920 0.095 0.031 0.000 0.000 0.000 0.000 0.118 Minimum 0.828 0.025 0.000 0.000 0.000 0.000 0.000 0.026 86
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Image Date Surface (km2) per NDVI Values Range
Month Day Year <= 0.1 0.1 - 0.2 0.2 - 0.3 0.3- 0.4 0.4 - 0.5 0.5 - 0.6 > 0.6 Total
June 14 1995 0.9261 0.019 0.001 0.000 0.000 0.000 0.000 0.020
June 16 1996 0.927 0.019 0.000 0.000 0.000 0.000 0.000 0.019
June 19 1997 0.9297 0.016 0.000 0.000 0.000 0.000 0.000 0.016
June 6 1998 0.9252 0.020 0.001 0.000 0.000 0.000 0.000 0.021
June 22 1998 0.9297 0.016 0.000 0.000 0.000 0.000 0.000 0.016
June 9 1999 0.9405 0.005 0.000 0.000 0.000 0.000 0.000 0.005
June 25 1999 0.936 0.010 0.000 0.000 0.000 0.000 0.000 0.010
June 15 2013 0.9459 0.000 0.000 0.000 0.000 0.000 0.000 0.000
Average 0.933 0.013 0.000 0.000 0.000 0.000 0.000 0.013
Maximum 0.946 0.020 0.001 0.000 0.000 0.000 0.000 0.021
Minimum 0.925 0.000 0.000 0.000 0.000 0.000 0.000 0.000
Image Date Surface (km2) per NDVI Values Range
Month Day Year <= 0.1 0.1 - 0.2 0.2 - 0.3 0.3- 0.4 0.4 - 0.5 0.5 - 0.6 > 0.6 Total
July 16 1995 0.9351 0.011 0.000 0.000 0.000 0.000 0.000 0.011
July 2 1996 0.9351 0.011 0.000 0.000 0.000 0.000 0.000 0.011
July 18 1996 0.9351 0.011 0.000 0.000 0.000 0.000 0.000 0.011
July 8 1998 0.9252 0.021 0.000 0.000 0.000 0.000 0.000 0.021
July 11 1999 0.9369 0.009 0.000 0.000 0.000 0.000 0.000 0.009
July 27 1999 0.9369 0.009 0.000 0.000 0.000 0.000 0.000 0.009
July 1 2013 0.9054 0.041 0.000 0.000 0.000 0.000 0.000 0.041
July 17 2013 0.8892 0.057 0.000 0.000 0.000 0.000 0.000 0.057
Average 0.925 0.021 0.000 0.000 0.000 0.000 0.000 0.021
Maximum 0.937 0.057 0.000 0.000 0.000 0.000 0.000 0.057
Minimum 0.889 0.009 0.000 0.000 0.000 0.000 0.000 0.009
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82 Image Date Surface (km2) per NDVI Values Range Month Day Year <= 0.1 0.1 - 0.2 0.2 - 0.3 0.3- 0.4 0.4 - 0.5 0.5 - 0.6 > 0.6 Total August 17 1995 0.9351 0.011 0.000 0.000 0.000 0.000 0.000 0.011 August 3 1996 0.9351 0.011 0.000 0.000 0.000 0.000 0.000 0.011 August 19 1996 0.9351 0.011 0.000 0.000 0.000 0.000 0.000 0.011 August 6 1997 0.9369 0.009 0.000 0.000 0.000 0.000 0.000 0.009 August 22 1997 0.9324 0.014 0.000 0.000 0.000 0.000 0.000 0.014 August 9 1998 0.9306 0.015 0.000 0.000 0.000 0.000 0.000 0.015 August 12 1999 0.9405 0.005 0.000 0.000 0.000 0.000 0.000 0.005 August 28 1999 0.9405 0.005 0.000 0.000 0.000 0.000 0.000 0.005 August 29 2011 0.9414 0.005 0.000 0.000 0.000 0.000 0.000 0.005 August 2 2013 0.8892 0.057 0.000 0.000 0.000 0.000 0.000 0.057 August 18 2013 0.8892 0.055 0.002 0.000 0.000 0.000 0.000 0.057 Average 0.928 0.018 0.000 0.000 0.000 0.000 0.000 0.018 Maximum 0.941 0.057 0.002 0.000 0.000 0.000 0.000 0.057 Minimum 0.889 0.005 0.000 0.000 0.000 0.000 0.000 0.005 Image Date Surface (km2) per NDVI Values Range Month Day Year <= 0.1 0.1 - 0.2 0.2 - 0.3 0.3- 0.4 0.4 - 0.5 0.5 - 0.6 > 0.6 Total October 4 1995 0.9225 0.023 0.000 0.000 0.000 0.000 0.000 0.023 October 20 1995 0.9234 0.022 0.001 0.000 0.000 0.000 0.000 0.023 October 6 1996 0.9315 0.014 0.000 0.000 0.000 0.000 0.000 0.014 October 22 1996 0.9279 0.018 0.000 0.000 0.000 0.000 0.000 0.018 October 9 1997 0.9279 0.016 0.002 0.000 0.000 0.000 0.000 0.018 October 25 1997 0.9216 0.020 0.005 0.000 0.000 0.000 0.000 0.024 October 13 2010 0.9387 0.007 0.000 0.000 0.000 0.000 0.000 0.007 Average 0.928 0.017 0.001 0.000 0.000 0.000 0.000 0.018 Maximum 0.939 0.023 0.005 0.000 0.000 0.000 0.000 0.024 Minimum 0.922 0.007 0.000 0.000 0.000 0.000 0.000 0.007 88
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Image Date Surface (km2) per NDVI Values Range
Month Day Year <= 0.1 0.1 - 0.2 0.2 - 0.3 0.3- 0.4 0.4 - 0.5 0.5 - 0.6 > 0.6 Total
November 23 1987 0.9297 0.013 0.004 0.000 0.000 0.000 0.000 0.016
November 10 1997 0.918 0.020 0.007 0.001 0.000 0.000 0.000 0.028
November 29 1998 0.9063 0.029 0.010 0.001 0.000 0.000 0.000 0.040
November 16 1999 0.9171 0.022 0.007 0.000 0.000 0.000 0.000 0.029
November 10 2000 0.9459 0.000 0.000 0.000 0.000 0.000 0.000 0.000
November 14 2010 0.9216 0.023 0.001 0.000 0.000 0.000 0.000 0.024
November 1 2011 0.9207 0.025 0.000 0.000 0.000 0.000 0.000 0.025
November 4 2015 0.936 0.010 0.000 0.000 0.000 0.000 0.000 0.010
Average 0.924 0.018 0.004 0.000 0.000 0.000 0.000 0.021
Maximum 0.946 0.029 0.010 0.001 0.000 0.000 0.000 0.040
Minimum 0.906 0.000 0.000 0.000 0.000 0.000 0.000 0.000
Image Date Surface (km2) per NDVI Values Range
Month Day Year <= 0.1 0.1 - 0.2 0.2 - 0.3 0.3- 0.4 0.4 - 0.5 0.5 - 0.6 > 0.6 Total
December 9 1996 0.9351 0.011 0.000 0.000 0.000 0.000 0.000 0.011
December 12 1997 0.9144 0.022 0.009 0.001 0.000 0.000 0.000 0.032
December 28 1997 0.9027 0.029 0.010 0.005 0.000 0.000 0.000 0.043
December 31 1998 0.9135 0.024 0.005 0.003 0.000 0.000 0.000 0.032
December 2 1999 0.9135 0.023 0.009 0.001 0.000 0.000 0.000 0.032
December 18 1999 0.9027 0.030 0.013 0.001 0.000 0.000 0.000 0.043
December 6 2015 0.9297 0.015 0.001 0.000 0.000 0.000 0.000 0.016
Average 0.916 0.022 0.007 0.001 0.000 0.000 0.000 0.030
Maximum 0.935 0.030 0.013 0.005 0.000 0.000 0.000 0.043
Minimum 0.903 0.011 0.000 0.000 0.000 0.000 0.000 0.011
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Annex II
Arcadis, 2017. Detailed Hydrogeological Study of the Silala River
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DETAILED HYDROGEOLOGICAL STUDY OF THE SILALA RIVER
Carolina Gómez (PhD)
Geology Specialist
Sebastián García
Project Geologist
Soledad Garcés
Project Geologist
May, 2017
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GLOSSARY The glossary of hydrogeological terms presented in this document is based on definitions from different glossaries prepared by trusted organizations. Some definitions that could not be found in those glossaries were taken from websites. The main sources are the following: British Geological Survey, 2017. Glossary of groundwater and groundwater-related termshttp://www.bgs.ac.uk/research/groundwater/resources/glossary.htmlSharp, J., 2007. A glossary of hydrogeological terms. Department of GeologicalSciences, University of Texas at Austin.World Meteorological Organization and United Nations Educational, Scientificand Cultural Organization, 2012. International Glossary of Hydrology.Alkalinity: Capacity of water to neutralise hydrogen ions by weak bases (mainly bicarbonate and carbonate), expressed in millimolecules of hydrogen ions per litre of water. Alluvial Deposits: Clay, silt, sand, gravel, pebbles or other detrital material deposited by flowing water. Aquifer: Geological formation capable of storing, transmitting and yielding exploitable quantities of water. Artesian Well: Well tapping a confined aquifer whose piezometric surface lies above the ground surface. Catchment Area: The area of land drained by a single stream or river or, in the case of karst, drained by a single doline or group of dolines. Catchment and watershed are equivalent terms. Confined/Artesian Aquifer: A confined aquifer is one containing groundwater that is under pressure exceeding atmospheric pressure. The recharge area to a confined aquifer is at some distance and is unconfined but at higher elevation than the confined aquifer. Discharge: Volume of water flowing per unit time, for example through a river cross-section or from a spring or a well. Drainage Network: The branching network of rivers and tributaries within a drainage basin. 94
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Electric conductivity: The ability of water to conduct electricity that is a function of
the ionic concentration [micromhos/cm or siemens].
Ephemeral Water Course: An ephemeral stream is one that remains dry during some
of the year. Flow can result from a rising water table intersecting the stream-bed or from
periods of surface flow.
Erosion: The action of surface processes that remove sediments from one location and
transport them it away to another location.
Exorheic: Draining into sea or ocean.
Flow: The rate of water discharges from a source expressed as a volume per unit time.
Synonymous with discharge.
Fluvial: Referring to processes occurring in a river.
Groundwater: Subsurface water occupying the saturated zone (i.e. where the pore
spaces (or open fractures) of a porous medium are full of water).
Headwaters: Sources of a river.
Hydraulic Conductivity: Property of a porous medium which, according to Darcy’s
law, relates the specific discharge to the hydraulic gradient.
Hydraulic Gradient: The change in hydraulic head per unit length in the direction of
flow, for example in a closed conduit, open channel or porous medium.
Hydrogeology: (1) The study of subsurface water, including its physical and chemical
properties, geologic environment, its role in geologic processes, natural movement,
recovery, contamination, and utilization; (2) the study of groundwater with particular
emphasis given to its chemistry, flow systems, and relation to the geologic environment
(Davis and DeWeist, 1966, p.1); (3) the study of water below the Earth's surface
(Pinneker, 1983, p.1).
Infiltration: The movement of water from the surface of the land into the subsurface.
Ions: Atom that becomes positively or negatively charged due to the loss or gain of an
electron (www.minerals.net/GlossaryMain.aspx).
Isotope: One of two or more species of atoms of a chemical element with the same
atomic number and position in the periodic table and nearly identical chemical
behaviour but with different atomic m.a.s.l.ses and physical properties. Every chemical
element has one or more isotopes (www.britannica.com/).
Meteoric Water: Water of recent atmospheric origin.
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Perennial Water Course: A definite stream of water in a definite natural channel, with well-defined bed and banks, from a definite source or sources of supply (legal definition). Perched System (or perched aquifer): Groundwater body, generally of moderate dimensions, supported by a relatively impermeable stratum and which is generally located between a deeper water table and the ground surface. Permeability: The ease with which a porous medium can transmit water or other fluids (normal expressed m/s or m/day). Pumping Test: A field testing procedure to quantify aquifer properties at a site involving pumping water out of (or less commonly injecting water into) an aquifer and measuring the effect on water levels in that aquifer and sometimes in adjacent strata. Recovery Test: Part of a pumping test consisting of the measurement, at predetermined time intervals, of the rise of the piezometric level or water table in a pumped well or in the surrounding observation wells after cessation of pumping. River Basin: Area having a common outlet for its surface runoff. River Bed: Lowest part of a river valley shaped by the flow of water and along which most of the sediment and runoff moves. River Thalweg: Line following the deepest part of a river. Runoff: 1) Water from precipitation, snowmelt, or irrigation running over the surface of the Earth; 2) Surface water entering rivers, lakes, or reservoirs; 3) A component of stream flow. Saturation: (in the context of soils or rocks) The state in which the pore spaces or open fractures of a porous medium are full of water – the definition of ‘groundwater’. Sediment: Material transported by water either in suspension or as bed load from the place of origin to the place of deposition. Spring: Place where water emerges naturally from the rock or soil and flows onto land or into a body of surface water. Stable Isotopes: A stable isotope of an element that shows no tendency to undergo radioactive breakdown (www.dictionary.com/browse/stable-isotope). Storage coefficient: Volume of water released from an aquifer, or taken into storage, per unit surface area of the aquifer in response to a unit change in head. Surface Water: Water which flows over or is stored on the ground surface. 96
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Transmissivity: Rate at which water is transferred through a unit width of an aquifer
under a unit hydraulic gradient.
Unconfined Aquifer: Saturated water-bearing formation, which has a water table open
to the atmosphere through permeable rock.
Underground Water: See Groundwater.
Water Level: Elevation of the free water surface of a water body relative to a datum
level.
Water Table: The surface of a body of unconfined groundwater at which the pressure
is equal to that of the atmosphere. The static water level in a well in an unconfined
aquifer.
Watershed: Basin syn. drainage basin, catchment, river basin. Area having a common
outlet for its surface runoff.
Wetland: Areas under or contiguous to open water or with a shallow water table,
including swamps, marshes, bogs, wet meadows, river overflows, mud flats, and natural
ponds. Wetlands are characterized by water-loving vegetation (phreatophytes or, in
areas with brackish water, halophytes).
Wells: Any artificial excavation or borehole constructed with the aim of either
exploring for or producing groundwater, or injection, monitoring or dewatering
purposes.
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TABLE OF CONTENTS 1 INTRODUCTION ........................................................................................................ 1 2 SUMMARY AND CONCLUSIONS ........................................................................... 5 3 LITERATURE REVIEW ............................................................................................. 8 3.1 Preliminary hydrogeological conceptual model from the literature review, and knowledge gaps ........................................................................................ 9 3.2 Design of field investigations .................................................................. 10 4 GEOLOGY ................................................................................................................. 11 4.1 Geology of the Silala River basin ............................................................ 11 4.1.1 Regional context ...................................................................................... 11 4.1.2 Evolution of the Silala River basin over geological time ........................ 12 5 FIELD INVESTIGATIONS ...................................................................................... 19 5.1 Well drilling campaign ............................................................................ 19 5.2 Stratigraphic logging of the borehole cuttings and core .......................... 22 5.3 Flow during drilling ................................................................................. 36 5.4 Pumping and recovery tests ..................................................................... 37 5.5 Geophysics .............................................................................................. 49 5.5.1 Borehole geophysics ................................................................................ 49 5.5.2 Electric resistivity tomography (ERT) .................................................... 56 5.6 Geomorphology ....................................................................................... 92 5.7 High definition topography ..................................................................... 98 5.8 Infiltration tests ........................................................................................ 99 5.9 Springs survey ....................................................................................... 103 5.10 Hydrochemical water sample collection ............................................... 111 5.11 Borehole fluid logging ........................................................................... 117 6 GEOLOGY AND HYDROGEOLOGY OF THE SILALA RIVER AND CATCHMENT ......................................................................................................... 123 6.1 Subsurface geology ............................................................................... 124 6.2 Aquifer parameters ................................................................................ 135 98
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6.3 Infiltration characteristics of the surface geologic units........................ 139
6.4 Hydrogeological units ........................................................................... 140
6.5 Water level analysis ............................................................................... 151
6.5.1 Water level map ..................................................................................... 151
6.5.2 Water level time series analysis ............................................................ 153
6.6 Hydrochemistry ..................................................................................... 156
6.6.1 Geochemistry data ................................................................................. 157
6.6.2 Environmental isotope data ................................................................... 162
6.7 Recharge ................................................................................................ 169
7 UNDERSTANDING OF THE HYDROGEOLOGY OF THE SILALA BASIN ... 170
8 REFERENCES ......................................................................................................... 176
9 ACKNOWLEDGEMENTS ..................................................................................... 178
LIST OF APPENDICES
Appendix A Summary of reports
Appendix B Pumping and recovery tests
Appendix C Geophysics
Appendix D High resolution topography
Appendix E Infiltration tests
Appendix F Borehole fluid logging
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1 1 INTRODUCTION The Dirección Nacional de Fronteras y Límites del Estado (DIFROL) of the Ministry of Foreign Affairs of Chile requested Arcadis to conduct technical studies to improve the understanding of the hydrogeological functioning of the Silala River basin, in the context of the Case Concerning the Status and Use of the Waters of the Silala, to be heard before the International Court of Justice in The Hague. The definition of the studies to be conducted was done jointly between Arcadis, Prof. José Muñoz and Prof. Francisco Suárez, both from the Pontificia Universidad Católica de Chile (UC) and the international experts advising DIFROL. This Report was produced under the supervision and instruction of DIFROL’s international experts, Dr. Denis Peach and Dr. Howard Wheater. The Silala River basin is a transboundary basin, located in the Second Region of Antofagasta, Chile (Figure 1-1), largely over 4000 m.a.s.l. elevation, in the Altiplano plateau. The watershed as defined by Alcayaga (2017) has a drainage area of some 95.5 km2, with 72% in Bolivian territory and 28% in the Chilean territory (Figure 1-2). An area was selected for detailed hydrogeological study within the Silala River basin, in Chilean territory, between an upper boundary close to the international border, located a few meters from the intake of The Antofagasta (Chili) and Bolivia Railway Company Ltd. (FCAB) (hereinafter the “FCAB Intake”), and the Inacaliri Police Station, extending some 5 km along the river course (Figure 1-3). The main objective of this study is to understand the hydrogeology of the Silala River basin and how it relates to the Silala River. This includes the following associated objectives: 1.To improve the knowledge of the geometry of the aquifer system(s) with whichthe Silala River might interact.2.To quantify the fluctuations in underground water levels along the river and inthe ravine of the river. To determine the hydraulic gradient and undergroundflow directions in the aquifer system(s).3.To determine the different groundwater sources that feed the river, identifyingtheir origin from the various aquifers.4.To analyse and model conceptually the hydrogeology of the Silala River basin,estimating aquifer parameters.In order to achieve these objectives, a review of existing data and literature was carried out as a basis for designing new field work and monitoring activities to infill the hydrogeological knowledge gaps. Subsequent to the literature review, a field campaign was designed and carried out during the period October 2016 to February 2017. A large amount of data was collected from field work that included borehole stratigraphy, 100
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borehole pumping and recovery tests, geophysics, high definition topography, and
hydrochemical sampling, among others. This information was organized, interpreted
and used to assess the different aspects of the hydrogeological conceptual model, which
summarizes the understanding of the hydrogeology of the Silala River basin.
This report presents a summary of the work and conclusions followed by a review of
existing data and reports, a description of the field work and analysis of the results, and
a summary conceptual hydrogeological model of the Silala River ravine and basin.
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3 Figure 1-1. General location map of the Silala River basin. 102
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Figure 1-2. The Silala River basin.
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5 Figure 1-3. Detailed location map of the study area. 2 SUMMARY AND CONCLUSIONS The hydrogeology of the Silala River has been assessed by analysing previous literature, the scientific reports produced by other members of the science team studying the Silala River during late 2016 and early 2017, and an extensive set of data collected specially for this purpose. This dataset includes borehole stratigraphy, borehole pumping and recovery tests, geophysics, high definition topography, and hydrochemical sample analyses, among others. The Silala River basin is a transboundary basin, with a drainage area of some 95.5 km2, with 72% in Bolivian territory and 28% in Chilean territory. The geology of the basin is dominated by volcanic rocks of different types (mainly volcanic sequences and ignimbrite), with ages ranging from Late Miocene (5.8 Ma 104
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(million years before present)) to Holocene (11.5 ky BP (thousand years before
present)). These rocks are covered by recent sediments: fluvial deposits, alluvial
deposits and pyroclastic fall deposits. The Silala River is incised into ignimbrite and has
deposited fluvial sands and gravels on top of the ignimbrite. A cross-border ravine is
between 10 and 100 m wide, with a mode of 20 m. Within the river ravine there are 4
fluvial terraces eroded into ignimbrite (T1, T2, T3 and T4), from ~2 m to ~20 m above
the current river thalweg, indicating past river activity. The current configuration of the
river was established after T2 was formed, well before about 8400 years BP.
The hydrogeology of the Silala River basin, in the study area, is characterized by the
presence of 6 hydrogeological units (HU): HU1 (Fluvial deposits), HU2 (Alluvial
deposits), HU3 (Ignimbrite), HU4 (Pyroclastic fall deposits), HU5 (Andesitic and
dacitic volcanic rocks) and HU6 (Weakly permeable rock). These categories have been
defined after field examination, geological mapping, drilling and other investigations,
although units outcropping in Bolivian territory could not be visited.
HU1 comprises moderate to high horizontal permeability Holocene fluvial deposits that
appear to be unsaturated over most of their distribution, except for a restricted zone
underneath the river, where they receive a water influx from the river directly above.
Vertical heterogeneity of the sediments is probably great (see Latorre and Frugone,
2017) and may lead to the river being perched in some places above the lower fluvial
sediments and also to perched water levels within the sediments. The fluvial deposits of
HU1 have no hydrogeological connection with the ignimbrite HU3 which they overlie.
HU2 corresponds to moderate to high horizontal permeability alluvial deposits of
different ages (Upper Pleistocene to Holocene), composed of gravel, sand and silt, with
a good distribution across the study area, mainly exposed in a planar surface to the north
and south of the Silala River ravine. HU2 is interpreted as supporting an extensive
perched aquifer or aquifers, which supply water to the many springs along the Silala
ravine and its tributaries. Some parts may be unsaturated and/or ephemeral.
HU3 is composed of two separate geological ignimbrite flow units: the Cabana
Ignimbrite (ca. 4.12 Ma) and the Silala Ignimbrite (ca. 2.6-1.48 Ma). The rock quality of
HU3 along the Silala ravine is very heterogeneous, with zones of fractures/faults and
zones that are strongly weathered, where the rock is very friable and permeable.
Groundwater levels obtained from wells and pumping tests indicate that HU3 contains
groundwaters that are confined. A confined aquifer is one containing groundwater that
is under pressure exceeding atmospheric pressure. The recharge area to a confined
aquifer is at some distance and is unconfined but at higher elevation than the confined
aquifer. Groundwater appears to flow through the ignimbrite rock HU3 from NE to SW,
a similar direction to the flow of the Silala River, and probably to the groundwater in
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7 the fluvial deposits HU1. Pumping tests and drilling results have shown the transmissivity and storage characteristics of these ignimbrites to vary considerably both laterally and vertically, indicating that these deposits may not act as one continuous aquifer but respond as several poorly connected aquifer(s). Borehole yields are highly variable and may be depth dependent in some areas HU4 comprises thin Pleistocene pyroclastic fall deposits (ca. 11.7 ky BP) of moderate to low permeability found in a restricted area. HU5 comprises possibly moderate to highly permeable lavas of the Lower Pleistocene (1.48 Ma) and other andesitic and dacitic volcanic rocks of the Lower Pleistocene (ca. 1.5 Ma). These rocks are the product of extrusion from the (now extinct) Cerro Inacaliri odel Cajón (henceforth Cerro Inacaliri) and Volcán Apagado, with outcrops in thehighest parts of the Silala basin, where the Cerro Inacaliri and Volcán Apagado are developed, and also in extensive lower areas, near the headwaters of the Silala River. HU5 is likely to have significant aquifer permeability and storage, as these are subaerial lava flows, which are likely to be highly porous and weathered. HU6 comprises all the other rocks in the study area, which are only weakly permeable. They mainly include Miocene-Pliocene Volcanic Sequences (ca. 5.8-2.6 Ma) and minor glacial deposits (ca. 40-12 ky BP). Miocene-Pliocene Volcanic Sequences are very heterogeneous with permeability restricted to zones with fractures, weathering and degassing zones (bubbles). Weathering takes place mainly in the uppermost 15 cm from the surface. The Glacial deposits are lateral or terminal moraines that are nonconsolidated, poorly sorted, clay-rich sediments, probably with low permeability. Geochemistry data indicate that the groundwater in the deep ignimbrite aquifer (HU3) is not related to the river water or the spring water. The groundwater is of low conductivity and of Calcium (Ca)-Bicarbonate type. On the other hand, the river and spring water has even lower conductivity and is Sodium (Na)-Bicarbonate type water with a relatively high content of Calcium. Environmental isotopes show that the recharge for the groundwater in the deep ignimbrite aquifer (HU3), river water, and springs in the upper course of the Silala River, Quebrada Negra and southern lower course of the Silala River is of regional nature, probably originating in the high Andes. On the other hand, recharge for the springs in the northern lower course of the Silala River is of a more local nature. Storage time appears to be highest (oldest water) in the groundwater of HU3, intermediate in the river water, and springs in the upper course of the Silala River, Quebrada Negra and southern lower course of the Silala, and lowest (youngest water) in springs in the northern lower course of the Silala River. Tritium analyses of river and 106
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spring water show that the waters contain very little tritium, indicating that the spring
waters are likely to have been recharged before 1960.
The recharge of the Silala River basin originates as precipitation in highlands, occurs
mostly during summer time and infiltrates into the surface rocks, soils and deposits
(HU1, HU2, HU3 and HU5), with probably little surface runoff and evaporation. The
water that infiltrates flows underground from high zones to lower zones, passing
through the various hydrogeological units.
Water that infiltrates into the alluvial sediments (HU2) flows downgradient and emerges
as springs in the rock walls of the ravine. In some cases this groundwater may travel
down through alluvial/colluvial fan deposits attached to the ravine walls and through
fluvial deposits (HU1), and finally reach the river in springs close to or in the river bed.
The fluvial sediments (HU1) exposed in the ravine have a limited outcrop area but are
often very permeable so rainfall would tend to infiltrate rapidly. Since the areal extent
of these deposits is very small, the impact of recharge is likely to be very small as well.
The recharge areas for the deep regional ignimbrite aquifer system (HU3) are unknown
but could include the large outcrop of Cabana Ignimbrite in Bolivia (northeast of the
Orientales wetland), and might also include the lavas on the sides of the Volcán
Apagado in Chile. The lateral and vertical heterogeneity of the ignimbrite aquifer(s)
means that they may respond independently and be recharged from differing sources.
Much of the precipitation over the Cerro Inacaliri and Volcán Apagado probably
infiltrates into the most recent andesitic lava flow products (HU5 Andesitic and dacitic
volcanic rocks), feeding the headwater springs that supply the Cajones and Orientales
wetlands. Some of this precipitation may run off these deposits, as flow through the soil
or overland, to recharge the shallow alluvial perched aquifers or the deep ignimbrite
aquifer at lower levels.
3 LITERATURE REVIEW
Table 3-1 lists the reports and scientific papers used to establish the knowledge base and
level of hydrogeological understanding. This includes one unpublished report (Hauser,
2004) which is particularly important, because of the detailed characterization of the
Silala River area, and especially the reports of information gained from the Silala River
spring sources in Bolivia. A summary of reports and an analysis of information
contained in each work is presented in Appendix A.
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9 Author Year Title Gayo et al. 2012 Late Quaternary hydrological and ecological changes in the hyper-arid core of northern Atacama Desert (~21ºS). Hauser 2004 Morphological, geological, tectonic, hydrogeological and hydrochemical context: morphogenesis, evolution and modalities of use of the shared Chilean-Bolivian hydrographic system of the Silala River. Sáez et al. 2016 Timing of wet episodes in Atacama Desert over the last 15 ky. The Groundwater Discharge Deposits (GWD) from Domeyko Range at 25°S. Table 3-1. Reports and scientific papers reviewed. 3.1 Preliminary hydrogeological conceptual model from the literature review, and knowledge gaps The Silala River basin is located in the Altiplano Plateau, with its headwaters and much of its surface area in Bolivian territory. The sources of the Silala River are found in groundwater-fed springs that feed two highland wetlands (Cajones and Orientales) typical of those found in the dry Altiplano region of the Andes (Hauser, 2004). The natural slope towards the west of the area ensures that the river discharges towards Chilean territory, which is typical of an exoreic basin of the Andean Highlands (Hauser, 2004). The Silala River basin has an arid to hyper-arid climate, which was established in the Late Pleistocene - early Holocene period, with at least 4 interspersed humid episodes (Gayo et al., 2012; Sáez et al., 2016). Hauser (2004) found that the solid geology of the Silala River basin is characterized by volcanic rocks with ages from Late Miocene to recent. The river and its headwaters eroded these volcanic rocks, in particular the Cabana Ignimbrite. The headwaters are found in highland wetlands that are fed by springs that emerge from the base of the sides and front of a lobe of a lava flow that was deposited on top of the Ignimbrite (Hauser, 2004). Two boreholes were drilled into ignimbrite rocks 2 km southwest of the international border, one of which was found to be artesian (Hauser, 2004) with a high flow. 108
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The surface water in the Silala River in Chilean territory and in its headwaters in
Bolivia is of sodium-bicarbonate type with low content of dissolved salts, which was
interpreted as being recharged from meteoric water associated with the present day local
rainfall pattern (Hauser, 2004).
The understanding of the hydrogeology of the Silala River basin at the time of the
review, as explained above, was very incomplete. Knowledge gaps include: detailed
geology and geomorphology, quantity and areas of recharge, heterogeneity of the
aquifer(s) and variability of aquifer parameters, groundwater level distribution in space
and over time, and hydrochemistry and its variation over time and space.
3.2 Design of field investigations
Geology is key to the understanding of the hydrogeology. At the time of this literature
review there was no geological map of the Silala basin at an adequate scale available
and little information about the subsurface from drilling or geophysics. Two wells
located along the Silala ravine about 200 m apart were believed to have been drilled into
ignimbrite. So, it was thought necessary to investigate the subsurface with a drilling and
pump testing campaign along the Silala ravine at three locations, at either end of the
study area (close to the international border and at the Inacaliri Police Station), and
slightly upstream of the junction with the Quebrada Negra. In order to extrapolate
between the drillhole information and investigate the subsurface on either side of the
river ravine, a geophysical survey using electrical resistivity tomography (ERT) was
proposed, together with Time Domain Electromagnetic (NanoTEM) studies to help with
validation of the ERT results. Surveys proposed included profiles along extended areas
as well as investigations of rock properties where the boreholes were to be drilled.
Additionally, the boreholes would be geophysically logged with depth to provide
information concerning water inflows and physical characteristics of the rocks
penetrated.
A geomorphologic study of the Silala River ravine was thought necessary to map the
river terraces. These geomorphological features are part of the late stage of evolution of
the study area. In order to achieve this, a high definition topographic survey was
proposed. This topography was also used to provide the base line topography needed to
reference the geophysical profiles and geological models.
Knowledge of the transmissivity or storage characteristics of the deep or shallow
aquifers was poor so a pumping and recovery test programme at the various drilling
sites was proposed and later carried out.
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11 In order to begin to understand recharge processes in the basin, an evaluation of the infiltration characteristics of the various geological units was made. A visual inspection of the course of the Silala River revealed many springs emerging from the walls and sometimes from the base of the ravine so a spring survey was carried out. A sampling survey of river water, spring waters and groundwater, with subsequent chemical analysis for major and minor ions, stable isotopes and other tracers and radiometric dating techniques, was thought necessary to provide information on the evolution of the groundwaters, their age and origins. Monitoring of the groundwater levels, whether confined groundwater piezometric heads or water table levels, would provide an indication of groundwater flow directions and temporal behaviour, which could perhaps provide indications of recharge events and recharge variability. 4 GEOLOGY 4.1 Geology of the Silala River basin 4.1.1 Regional context The regional geology as seen at outcrop is the result of a series of episodic volcanic processes and events that have taken place over approximately the last 12 Ma (SERNAGEOMIN, 2017). The oldest rocks that outcrop in the region comprise tuffs that in-filled the palaeo-topography. The radiometric ages of these rocks indicated at least two similar volcanic events dated as ca. 11.48 Ma and ca. 8.33 Ma (SERNAGEOMIN, 2017). These rocks represent part of a series of voluminous and extensive volcanic events that affected this part of the Altiplano. Ignimbrites were deposited from explosive volcanic eruptions. These volcanoes extruded a mix of volcanic gases, molten rock and ash in a highly fluid pyroclastic flow. These flow under gravity at speeds of up to 100 km/hour and are very destructive. After 6.2 Ma (SERNAGEOMIN, 2017) came the growth of volcanic edifices on and through a basement of ignimbrite bedrock (Figure 4-1 and Figure 4-2). These stratovolcanoes created a 30 km volcanic mountain chain along a NW-SE direction, including the Cerro Inacaliri, which lies on the northern side of the Silala River. The earliest lavas of the Inacaliri volcanic centre have been dated at ca. 5.8 Ma (SERNAGEOMIN, 2017). 110
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Then, at ca. 4.12 Ma (SERNAGEOMIN, 2017) the Cabana Ignimbrite was deposited in
the Altiplano (Figure 4-1 and Figure 4-2). This was a voluminous and highly evolved
deposit and filled much of the pre-existing topography.
The volcanic activity continued in the north at the Inacaliri volcano and to the south
with the development of the Volcán Apagado (Figure 4-1 and Figure 4-2).
The most recent volcanic activity in the area is represented by the pyroclastic fall
deposits that resulted from an eruption of the Volcán San Pedro, located immediately
east of the Silala River basin. These have been dated at the beginning of the Holocene
(11.5 ky; Bertin and Amigo, 2015) (Figure 4-1 and Figure 4-2).
4.1.2 Evolution of the Silala River basin over geological time
This section describes the evolution of Silala River basin and ravine, and is
diagrammatically depicted in Figure 4-3. This sequence of events is based on the
understanding of the stratigraphy of the Silala River basin as can be seen in the
schematic stratigraphic column (Figure 4-1) and geological map (Figure 4-2) prepared
by SERNAGEOMIN (2017). This section also summarizes the depositional and
erosional events that took place in the ravine from about ca. 8.4 ky to present (Latorre
and Frugone, 2017) and the archaeological evidence of human activity and habitation
along the Silala River (McRostie, 2017).
The geology of the Silala River basin is dominated by a series of volcanic episodes
interspersed with periods of sedimentary activity, during a time of active tectonics, over
the last ca. 6 Ma. The volcanic rocks deposited earlier (see above) are labelled as
undifferentiated basement in Figure 4-3.
The period between ca. 5.8-2.6 Ma was characterized by acidic volcanism that included
the emplacement of volcanoes, domes, volcanic vents and the extrusion of lavas and
ignimbrites (Figure 4-3, panels 1-3). This created the oldest positive relief in the area
(e.g. early development of Cerro Inacaliri and Cerrito de Silala over about 5.8 Ma to
about 2.6 Ma). During this same period, a very large eruption in the east resulted in the
deposition of the Cabana Ignimbrite, dated at ca. 4.12 Ma (Figure 4-3, panel 2).
Subsequently during the late Pliocene and early Pleistocene (ca. 2.6 Ma - 1.5 Ma) the
Silala River basin was subject to local compressive faulting which exposed and tilted
the Cabana Ignimbrite deposits (Figure 4-3, panel 3). During this period the first
evidence of fluvial activity or a proto-Silala river (Figure 4-3, panel 4 Silala 1) arises,
given by the occurrence of sandstone and conglomerate in the vicinity of the Inacaliri
Police Station and coarse grained sedimentary breccia in a cored borehole. These
deposits are interpreted as a product of alluvial sedimentation.
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13 Subsequent to this fluvial deposition, the Silala Ignimbrite was deposited in the proto-Silala valley (Figure 4-3, panel 5). At about 1.5 Ma, the Inacaliri volcano became active again and the Volcán Apagado was formed. An extensive lava flow was deposited on the eastern side of the Inacaliri volcano. This flowed into the headwaters of the proto-Silala River, truncating a previously established drainage system (Figure 4-3, panel 6) (SERNAGEOMIN, 2017). After a period of about 1.5 Ma for which there is no geological record, the area was subject to glaciation near the tops of the mountain peaks. Moraines were deposited towards the end of the last glacial maximum, developed during the late Pleistocene (ca. 40-12 ky BP) on the side of Cerro Inacaliri at levels above approximately 4400 m.a.s.l. Alluvial fan deposits can be found interdigitating with the glacial moraine downslope on the hillside (Figure 4-3, panel 7). Dating from about 11.5 ky ago the last evidence of volcanic activity can be found in thin pyroclastic fall deposits, probably derived from an eruption of the San Pedro volcano (20 km east of Inacaliri Police Station) (SERNAGEOMIN, 2017). The geomorphology of the Silala River, as it can be seen today, was established before about 8.4 ky BP (Latorre and Frugone, 2017) (Figure 4-3, panel 8). The landform along the Silala ravine is characterized by four mapped river terraces (erosional features) and with four different sedimentary depositional units (Figure 4-4) (Latorre and Frugone, 2017). Organic materials found in associated palaeo-wetland deposits were Carbon-14 dated, indicating depositional and erosional activity for over about 8400 years ago to the present. Archaeological evidence shows that the Silala River and its ravine provided water resources and fodder to pre-Columbian and more recent human communities that travelled through the Altiplano (McRostie, 2017). 112
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Figure 4-1. Diagram of the Stratigraphic column of the Silala River basin. Blue line represents
the morphostratigraphic position of the river ravine with its associated river deposits (Holocene
evolution of Silala River: T1 to T3; see detailed evolution in Latorre and Frugone (2017)).
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114
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Figure 4-2. Geology of the Silala River Basin. (A) Geological map and profiles, (B) Legend of
geological units. (SERNAGEOMIN, 2017).
B
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17 Figure 4-3. Diagram of the geological and morphological evolution of the Silala River area. Reference: SERNAGEOMIN (2017). 116
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Figure 4-4. Sedimentary deposits found within the Silala ravine and associated terraces (from
Latorre and Frugone, 2017).
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19 5 FIELD INVESTIGATIONS The field investigations were designed to go some way to fill the knowledge gaps identified in Chapter 3. The data acquired were grouped into 11 topics: 1.Well drilling campaign.2.Stratigraphic logging of the borehole cuttings and core.3.Flow during drilling.4.Pumping and recovery tests.5.Geophysics.6.Geomorphology.7.High definition topography.8.Infiltration tests.9.Springs survey.10.Hydrochemical water sample collection and chemical and isotopic analysis.11.Borehole fluid logging.5.1 Well drilling campaign The purpose of the drilling was to investigate the subsurface to depths of approximately 80-120 metres below ground level (m.b.g.l.), geologically and hydrogeologically, to establish a better understanding of groundwater occurrence and its relationship to the Silala River. A further aim was to establish the presence of any substantive aquifers beneath the river. In the study area, 8 boreholes were drilled during November 2016 with a total accumulated depth of drilling of 727.5 m (Table 5-1 and Figure 5-1). The previous drilled boreholes are included in Table 5-1 and Figure 5-1 for clarity. 118
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Well
Coordinates WGS84,
19S
Ground
altitude
(m.a.s.l.)
Class 1 Class
2
Stick up
elevation
(m.a.s.l.)
Total
depth
(m.b.g.l.)
Drilling
system
E N
MWBO
600191.62 7565286.96 4273.09 Monitoring New 0.76 10.00
Dual
Rotary
PWBO
600185.09 7565278.32 4272.62 Pumping New 0.76 80.00
Dual
Rotary
CWBO
600174.71 7565266.58 4272.60 Monitoring New 0.63 117.00
Core
drilling
MWLUQN
599352.86 7564072.18 4205.13 Monitoring New 0.72 60.00
Dual
Rotary
PWUQN
599346.41 7564063.25 4204.59 Pumping New 0.53 80.00
Dual
Rotary
MWSUQN
599339.82 7564051.92 4204.14 Monitoring New 0.72 10.00
Dual
Rotary
SPWDQN
599091.11 7563870.57 4189.80 Artesian Old 0.00 70.00 Unknown-
PWDQN
598838.65 7563779.89 4178.47 Pumping Old 0.32 54.00 Unknown
MWDQN
598841.32 7563769.18 4179.38 Monitoring New 0.90 40.00
Dual
Rotary
EWPS
596388.24 7563832.86 4032.16 Exploration New 0.84 94.00
Dual
Rotary
PWUQI
597103.26 7564812.05 4188.54 Exploration Old 0.67 182.50 Unknown
Table 5-1. New wells and previous wells in the Silala River basin.
The boreholes were drilled in 3 different locations along the ravine of the Silala River:
at the border (BO), upstream of the Quebrada Negra (UQN), and at the Inacaliri Police
Station (PS). Also, there are two old boreholes downstream of the Quebrada Negra
(DQN). The BO location is of high interest, since it corresponds to the easternmost
point of the Silala ravine in Chile. UQN and DQN are important because they can be
used to characterize the geology and hydrogeology upstream and downstream of the
junction of the Quebrada Negra and the Silala River. Finally, the PS location can be
used to understand the hydrogeology at the western end of the study area at a
downstream position of the Silala River, close to the CODELCO surface water
abstraction intake structure (Figure 5-1).
All of the boreholes were drilled with a reverse circulation air-water rotary system,
except for well CW-BO, which was wireline diamond cored (Table 5-1). At each of the
three sites, a large diameter well that was to be pumped was constructed, together with a
shallow and deep observation borehole. The cored borehole was completed as an
observation borehole. A further observation borehole was drilled close to PW-DQN (old
name - Silala No 1), first drilled in 1995. At the PS site only one large diameter
borehole was constructed. This proved to be dry so no monitoring boreholes were
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21 drilled. Figure 5-1 and Figure 5-2 show the location of new and previously drilled wells and all the wells classified by use, respectively. Figure 5-1. New wells and previous wells in the study area. 120
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Figure 5-2. Wells in the study area, classified by use.
5.2 Stratigraphic logging of the borehole cuttings and core
The stratigraphy of the boreholes was interpreted from descriptions of the drilling
cuttings from 7 boreholes and the detailed geological log of the cored borehole.
Based on well logging, 3 geological units have been identified. From youngest to oldest
these are:
1. Fluvial deposits.
2. Silala Ignimbrite.
3. Cabana Ignimbrite.
Table 5-2 and Table 5-3 show the depth below ground level and thickness of the three
identified geological units in the new and pre-existing boreholes. The stratigraphy and
construction details can be seen from Figure 5-3 to Figure 5-13.
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23 It should be noted that the base of the Cabana Ignimbrite was not reached in any of the boreholes drilled. Well Depth (m.b.g.l.) Thickness (m) From To PW-UQI 0.0 0.0 0.0 PW-BO 0.0 6.0 6.0 MW-BO 0.0 5.0 5.0 PW-UQN 0.0 6.0 6.0 MWS-UQN 0.0 6.0 6.0 MWL-UQN 0.0 6.0 6.0 EW-PS 0.0 18.0 18.0 CW-BO 0.0 6.4 6.4 PW-DQN 0.0 9.0 9.0 MW-DQN 0.0 8.0 8.0 SPW-DQN 0.0 13.0 13.0 Table 5-2. Depth below ground level and thickness of the fluvial deposits in new and old boreholes. Well Depth (m.b.g.l.) Thickness (m) From To PW-UQI 27.0 53.0 26.0 PW-BO 6.0 65.0 59.0 MW-BO 5.0 12.0 7.0 PW-UQN 6.0 48.0 42.0 MWS-UQN 6.0 10.0 4.0 MWL-UQN 6.0 47.0 41.0 EW-PS 0.0 0.0 0.0 CW-BO 6.4 64.0 57.6 PW-DQN 9.0 62.0 53.0 MW-DQN 8.0 40.0 32.0 SPW-DQN 13.0 58.0 45.0 Table 5-3. Depth below surface and thickness of the Silala Ignimbrite in new and old boreholes. 122
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Well Depth (m.b.g.l.) Thickness (m)
From To
PW-UQI 53.0 182.5 129.5
PW-BO 65.0 80.0 15.0
MW-BO 0.0 0.0 0.0
PW-UQN 48.0 80.0 32.0
MWS-UQN 0.0 0.0 0.0
MWL-UQN 47.0 60.0 13.0
EW-PS 18.0 97.0 79.0
CW-BO 64.0 117.0 53.0
PW-DQN 0.0 0.0 0.0
MW-DQN 0.0 0.0 0.0
SPW-DQN 58.0 70.0 12.0
Table 5-4. Depth below surface and thickness of the Cabana Ignimbrite in new and old
boreholes.
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25 Figure 5-3. CW-BO Well Completion and Stratigraphy. 124
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Figure 5-4. MW-BO Well Completion and Stratigraphy.
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27 Figure 5-5. PW-BO Well Completion and Stratigraphy. 126
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Figure 5-6. MWL-UQN Well Completion and Stratigraphy.
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29 Figure 5-7. PW-UQN Well Completion and Stratigraphy. 128
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Figure 5-8. MWS-UQN Well Completion and Stratigraphy.
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31 Figure 5-9. PW-DQN Well Completion and Stratigraphy. 130
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Figure 5-10. MW-DQN Well Completion and Stratigraphy.
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33 Figure 5-11. SPW-DQN Well Completion and Stratigraphy. 132
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Figure 5-12. PW-UQI Well Completion and Stratigraphy.
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35 Figure 5-13. EW-PS Well completion and stratigraphy. 134
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5.3 Flow during drilling
Flow measured during drilling can be used to understand the hydrogeological behavior
of the drilled geological units. During the drilling process, water was found in 6 out of 8
boreholes (Table 5-5). In most of the cases (except for cored borehole CW-BO), a depth
of water influx could be identified and discharge was measured.
Well
Total
depth
(m.b.g.l.)
Water influx
fluvial (m)
Water influx
ignimbrite (m)
Estimated
discharge from
ignimbrite (l/s)
MW-BO 10.00 no none
PW-BO 80.00 no 23
PW-BO 80.00 no 29 3.5
PW-BO 80.00 no 60 7.5
PW-BO 80.00 no 61-80
Water influx
increases
PW-BO 80.00 no Final airlift 10.4
CW-BO 117.00 - -
MWL-UQN 60.00 no 15
PW-UQN 80.00 no 14
PW-UQN 80.00 no 16 4.2
PW-UQN 80.00 no 40 9.3
PW-UQN 80.00 no 52-62
Water influx
increases
PW-UQN 80.00 no 72-78
Water influx
increases
PW-UQN 80.00 no Final airlift 20
MWS-UQN 10.00 no no
MW-DQN 40.00 no 20
EW-PS 94.00
yes (18m, fluvialignimbrite
contact) 22, 65, 71*
Table 5-5. Flow during drilling of the boreholes. Water influx from different units and estimated
discharge is shown.
* The water influx did not allow measurement of the water level. Water influxes were very little
and were not able to be measured.
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37 5.4 Pumping and recovery tests Pumping tests were designed to understand the Silala basin aquifers and estimate the hydrogeological aquifer properties (Transmissivity and Storage Coefficient) at each site. Between November 23rd and December 9th, pumping and recovery tests were performed in 3 out of the 4 locations named above: BO, UQN and DQN (Table 5-6 and Figure 5-2) in 3 purpose drilled boreholes, PW-BO, PW-UQN and PW-DQN. Appendix B contains the pumping and recovery test interpretation report. The results of Step-Drawdown and Constant-Rate tests are shown from Figure 5-14 to Figure 5-25. Location Pumping well Monitoring well Distance between wells Location Date of pumping initiation Date of last recovery measurement BO PW-BO CW-BO 15.7 Border (BO) 11/28/16 12/02/16 UQN PW-UQN MWL-UQN 11.0 Upstream Q. Negra (UQN) 11/23/16 11/26/16 DQN PW-DQN MW-DQN 11.0 Downstream Q. Negra (DQN) 12/06/16 12/09/16 Table 5-6. Pumping and recovery tests in the Silala ravine. 136
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Figure 5-14. Step-Drawdown test in borehole PW-BO.
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39 Figure 5-15. Step-Drawdown test in borehole CW-BO. 38Figure5-14.Step-Drawdown testin borehole PW-BO.
138
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Figure 5-16. Water drawdown during Constant-Rate test in PW-BO pumping well.
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41 Figure 5-17. Water drawdown during Constant-Rate test in CW-BO observation well. 140
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Figure 5-18. Step-Drawdown test in borehole PW-UQN.
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43 Figure 5-19. Step-Drawdown test in borehole MWL-UQN. 142
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Figure 5-20. Water drawdown during Constant-Rate test in PW-UQN pumping well.
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45 Figure 5-21. Water drawdown during Constant-Rate test in MWL-UQN pumping well. 144
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Figure 5-22. Step-Drawdown test in borehole PW-DQN
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47 Figure 5-23. Step-Drawdown test in borehole MW-DQN 146
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Figure 5-24. Water drawdown during Constant-Rate test in PW-DQN pumping well.
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49 Figure 5-25. Water drawdown during Constant-Rate test in MW-DQN observation well. 5.5 Geophysics 5.5.1 Borehole geophysics Gamma ray and Neutron Porosity geophysical logs were carried out in 6 of the boreholes: PW-BO, PW-UQN, MWL-UQN, PW-DQN, MW-DQN, and EW-PS (Figure 5-26 to Figure 5-31). The results and analysis are shown in Appendix C. 148
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Figure 5-26. Gamma ray and Neutron Porosity Geophysical log in Borehole PW-BO.
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51 Figure 5-27. Gamma ray and Neutron Porosity Geophysical log in Borehole PW-UQN. 150
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Figure 5-28. Gamma ray and Neutron Porosity Geophysical log in Borehole MWL-UQN.
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53 Figure 5-29. Gamma ray and Neutron Porosity Geophysical log in Borehole PW-DQN. 152
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Figure 5-30. Gamma ray and Neutron Porosity Geophysical log in Borehole MW-DQN.
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55 Figure 5-31. Gamma ray and Neutron Porosity Geophysical log in Borehole EW-PS. 154
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5.5.2 Electric resistivity tomography (ERT)
An ERT survey was carried out along and across the Silala River. The purpose of the
survey was to establish broad electrical properties of the top 100-200 metres of the
subsurface. These might then be used to indicate the likelihood of significant
groundwater occurrence or lithological changes in the subsurface at these depths. The
design of the survey included key zones under investigation: Silala River ravine, a
section of the Silala River ravine at Chile-Bolivia border, the alluvial plain underneath
the Inacaliri volcano, and a section across the Silala River ravine at ravines like the
Quebrada Negra and Quebrada Inacaliri.
This included 6576 stations and over 85 kilometres of linear survey, shown on Figure
5-32. The tomography profiles were supplemented by 18 depth soundings using Time
Domain Electromagnetic methods (NanoTEM) to provide depth control and electrical
parameters for interpreting the tomography profiles. The surveys were carried out by
Geodatos.
Results are shown from Figure 5-33 to Figure 5-66, and detailed analysis can be found
in Appendix C.
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57 Figure 5-32. Location of ERT lines, NanoTEM soundings and well-logging. 156
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Figure 5-33. ERT Profile L1.1
1 This and the following figures can be found in pdf format in the Data CD, Geodatos Folder.
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59 Figure 5-34. ERT Profile L2.1. 158
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Figure 5-35. ERT Profile L2.2.
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61 Figure 5-36. ERT Profile L2.3. 160
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Figure 5-37. ERT Profile L3.
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63 Figure 5-38. ERT Profile L4.1. 162
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Figure 5-39. ERT Profile L4.2.
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65 Figure 5-40. ERT Profile L4.3. 164
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Figure 5-41. ERT Profile L5.
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67 Figure 5-42. ERT Profile L6.1. 166
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Figure 5-43. ERT Profile L6.2.
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69 Figure 5-44. ERT Profile L6.3. 168
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Figure 5-45. ERT Profile L6.4.
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71 Figure 5-46. ERT Profile L6.5. 170
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Figure 5-47. ERT Profile L6.6.
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73 Figure 5-48. ERT Profile L6.7. 172
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Figure 5-49. ERT Profile L7.1.
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75 Figure 5-50. ERT Profile L7.2. 174
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Figure 5-51. ERT Profile L7.3.
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77 Figure 5-52. ERT Profile L7.4. 176
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Figure 5-53. ERT Profile L7.5.
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79 Figure 5-54. ERT Profile L7.6. 178
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Figure 5-55. ERT Profile L7.7.
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81 Figure 5-56. ERT Profile L7.8. 180
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Figure 5-57. ERT Profile L7.9.
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83 Figure 5-58. ERT Profile L7.10. 182
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Figure 5-59. ERT Profile L7.11.
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85 Figure 5-60. ERT Profile L7.12. 184
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Figure 5-61. ERT Profile L7.13.
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87 Figure 5-62. ERT Profile L7.14. 186
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Figure 5-63. ERT Profile L7.15.
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89 Figure 5-64. ERT Profile L7.16. 188
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Figure 5-65. ERT Profile L8.
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91 Figure 5-66. ERT Profile L9.
190
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92 5.6 Geomorphology The Silala River has cut a ravine into the Silala Ignimbrite and deposited fluvial sands and gravels upon this bedrock. The ravine is between 10 and 100 m wide, with a mode of 20 m. Four river terraces can be found in the ravine. From youngest to oldest, they are: T1 (~1-2 m above the thalweg), T2 (~5-6 m above the thalweg), T3 (~10 m above the thalweg), and T4 (~20 m above the thalweg) (Figure 5-67). Their development is variable in different sections of the ravine. These terraces were identified on site with the SERNAGEOMIN team and Claudio Latorre, and subsequently were mapped in detail using the DTM and high resolution mosaic (see section 5.7) (Figure 5-68, Figure 5-69, and Figure 5-71) developed by Arcadis. Terrace T1 is 1-2 m above the present erosion surface of the river and is located along the entire riverside. Terrace T2 is well developed in the area where the Quebrada Negra converges with the Silala River. This terrace mainly features an abrasion terrace. It takes the form of near vertical walls on either side of the river, at an approximate height of 5-6 m above the river bed, but does not show much lateral development. It is located between 1 and 2 metres above a linear indentation visible on both sides of the ravine. This appears to be the result of erosion due to a change in lithology in the ignimbrite resulting in a change in hardness. Terrace T2 can be followed for several hundred metres along the river. About 900 m west of the junction of the Quebrada Negra with the Silala River, the same erosion level was detected in the walls of the ravine. In this area, terraces T3 and T4 were also identified (Figure 5-67). Terrace T3 is found approximately 10 m above the river bed, while terrace T4 is about 20 m above the river level. Terraces T3 and T4 show greater lateral development than terrace T2, having erosion surfaces several tens of metres wide. At the coordinates (600.050E, 7.565.185N) terrace T3 forms a 15-20 m plain along a 100 m axis. Here it is possible to see various signs of fluvial erosion, including an excavation overhang (cavetto) (Figure 5-71) caused by a water course. In the same figure the level of a previous river bed with carbonate deposition along a horizontal line in the wall of the erosional overhang can be seen. On the surface of terrace T4 imbricated (directionally aligned) clasts were identified (Figure 5-72). These are interpreted as indicating fluvial flows from the alluvial deposits higher on the side of the Cerro Inacaliri and material transport to the ravine. These clasts Annex II
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93 appear to be associated with alluvial fans that originate in the hills on either side of the river ravine. The youngest erosional terrace in the Silala ravine (T2) represents a bedrock valley floor that formed before the erosion of the current ravine and the deposition of the sedimentary units present within the current ravine (Latorre and Frugone, 2017). The oldest radiocarbon date for sediments deposited in the ravine is 8430-8350 years BP, but these are not the oldest sediments. Terraces T3 and T4 represent older erosional valley floor surfaces. It is reasonable therefore to conclude that the present course of the Silala River dates from well before the dated sediments. Figure 5-67. Abrasion terraces on top of Cabana Ignimbrite due to activity of the Silala River. 192
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Figure 5-68. General map of the study area including location of boreholes and the terraces
identified in the Silala River ravine.
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95Figure 5-69. Identification of terracesin east slope of the Silala River ravine, 50 m southwestofthe international border. 194
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Figure 5-70. Identification of terraces on west slope of the Silala River ravine, 300 m southwest
of the international border.
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97 Figure 5-71. Excavation overhang in terrace T3. Blue line indicates level at which carbonates were deposited, marking the river level. Figure 5-72. Imbricated clasts in terrace T4. 196
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5.7 High definition topography
In order to establish the detailed topographic variation of the Silala ravine and adjacent
areas of hillside, a high-resolution image survey was carried out. This was flown using
drones and in parallel, reference points were surveyed with differential GPS to allow the
images to be accurately georeferenced.
Using these data, a high resolution digital surface model (DSM) and a digital terrain
model (DTM) were made (each pixel being 5x5x5 cm), covering a total surface area of
some 12 km2, with 18 calibration stations measured with differential GPS (Figure 5-73).
A high-resolution image of the ravine based on 5,055 calibrated images was created.
The merging of these images resulted in a mosaic having a resolution of 5x5x5 cm per
pixel. The high resolution of this image means that computers with very large memory
are required to manipulate the data so images having lower resolutions - of 10x10x10
cm, 25x25x25 cm, and 50x50x50 cm - were also generated for modelling purposes.
The DTM was subsequently up-loaded into the LeapFrog 3D modelling software
(http://www.leapfrog3d.com/) with a resolution of 1x1x1 m, so that geological
interpretations in 3D could be undertaken with the geophysical and drilling geological
data.
Appendix D contains the report on the topography survey that was carried out.
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99 Figure 5-73. Drone calibrated points, ground control points (GPS), and background mosaic. 5.8 Infiltration tests In order to characterise the permeability and infiltration capacity of the various geological units, infiltration tests were performed at 10 locations in the study area using double-ring infiltrometer and Guelph permeameter methods (Table 5-7 and Figure 5-74). The results are shown in Figure 5-75 (double ring) and Figure 5-76 (Guelph permeameter); analysis of the test results can be found in Appendix E. 198
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ID Method UTM E
(m)
UTM N
(m) Date Geology
I1 Double ring 599.582 7.564.843 19-12-2016 Alluvial deposits Pls(a)
I2 Double ring 597.151 7.564.717 18-12-2016 Alluvial deposits Pls(a)
I3 Double ring 598.026 7.562.578 18-12-2016 Pyroclastic fall deposits
PlH(pc)
I4 Guelph perm. 597.768 7.562.227 19-12-2016 Miocene-Pliocene lavas
MsPvd
I5 Guelph perm. 599.847 7.562.063 22-12-2016 Miocene-Pliocene lavas
MsPvd
I6 Guelph perm. 597.429 7.560.157 19-12-2016 Cabana Ignimbrite Piic
I7 Double ring 600.123 7.565.216 18-12-2016 Fluvial deposits Hf
I8 Double ring 596.471 7.563.867 17-12-2016 Fluvial deposits Hf
I9 Guelph perm. 598.897 7.563.890 19-12-2016 Silala Ignimbrite Pliis
I10 Guelph perm. 601.503 7.560.285 19-12-2016 Pliestocene lavas Pliv(a)
Table 5-7. Location and description of the infiltration test points.
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101 Figure 5-74. Location of infiltration tests. 200
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Figure 5-75. Double ring infiltration test results.
y = 0.296x + 2.1399
R² = 0.9976
0
10
20
30
40
50
60
70
80
90
0 50 100 150 200 250 300
Drawdown (cm)
Time (min)
I-8
y = 0.0141x + 0.0344
R² = 0.9655
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
0 20 40 60 80 100 120 140
Drawdown (cm)
Time (min)
I-3
y = 0.5411x - 0.4203
R² = 0.9998
0
10
20
30
40
50
60
70
80
90
0 20 40 60 80 100 120 140 160
Drawdown (cm)
Time (min)
I-1
y = 0.2074x + 1.0133
R² = 0.9965
0
5
10
15
20
25
30
0 20 40 60 80 100 120 140
Drawdown (cm)
Time (min)
I-7
y = 1.8089x - 0.3429
R² = 0.9997
0
10
20
30
40
50
60
70
80
90
0 10 20 30 40 50
Drawdown (cm)
Time (min)
I-2
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103 Figure 5-76. Guelph permeameter infiltration test results. 5.9 Springs survey A total of 37 springs have been located in the Silala ravine and its tributaries (Figure 5-77 and Table 5-8). The spring survey was performed in the last week of January 2017. During the campaign, 33 sites were surveyed, registering time and their location with GPS. Temperature and conductivity of each of the springs were also measured. This information was complemented with 3 spring sites provided by Suárez et al. (2017) and 1 spring site found during the 2016 hydrochemistry campaign. Their spatial locations are presented in Figure 5-77 and in Table 5-8. y = 1.9626x + 3.9611R² = 0.999051015202530354005101520Drawdown (
cm)Time (min)I-4y = 1.2115x + 0.9543R² = 0.9997051015202505101520Drawdown (
cm)Time (min)I-5y = 2.0683x + 7.0145R² = 0.998605101520253035404505101520Drawdown (
cm)Time (min)I-6y = 1.6373x + 4.2047R² = 0.99940510152025303505101520Drawdown (
cm)Time (min)I-9y = 4.257x + 2.9657R² = 0.99970102030405060708005101520Drawdown (
cm)Time (min)I-10104Springs 202
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Springs have been grouped into FCAB springs and other springs. FCAB springs (spring
name SP-FCAB-x in Table 5-8) correspond to those along the Silala ravine, which have
been labelled on the rock walls by FCAB. Other springs are labelled as SP-NNx or SPSI-
x (sampled for hydrochemical analysis) in Table 5-8.
From the total of 37 springs, 32 are located in the Silala ravine, 4 are located within 1
km of the ravine (along creeks like the Quebrada Negra and Quebrada Inacaliri) and 1 is
located about 4.5 km south of the Silala ravine, along the Quebrada Cabana (Figure
5-77 and Table 5-8). As can be seen in Figure 5-77, most of the springs (29) are located
along the Silala ravine, between the international border and the junction with Quebrada
Negra. This is where 23 FCAB springs and 6 other springs have been found.
Temperatures between 11.5 °C and 21.5 °C were measured. In the springs downstream
of the junction of the Silala River and Quebrada Negra, the highest temperatures were
measured, between 18.5 °C and 21.5 °C. Upstream of the junction, temperatures were
lower: between 11.5 °C and 16.6°C (Figure 5-78). The temperatures of the spring
waters were compared to the average January ambient air temperature (Muñoz et al.,
2017) and are thought to relate primarily to groundwater temperatures.
The electrical conductivities varied between 80 and 300 uS/cm, but with no discernable
pattern in the spatial distribution (Figure 5-79).
Out of the 37 springs, 27 emerge from ignimbrite rock in the walls of the ravine and 10
emerge as flow from the soil (either from alluvial/colluvial deposits on the sides of the
ravine or fluvial deposits in the base of the ravine), as seen in Figure 5-80.
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105 Figure 5-77. Location of the springs present in the study area. 204
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Figure 5-78. Temperature distribution of springs.
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107 Figure 5-79. Electric conductivity distribution of springs. 206
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Figure 5-80. Springs, classified by source of water.
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109 Spring name X (WGS84) Y (WGS84) Altitude (m.a.s.l.) Date Time Temperature (°C) Conductivity (μS/cm) SP-FCAB-1 599926 7564847 4320 31/01/2017 18:07 15.6 131 SP-FCAB-2 599932 7564890 4194 02/02/2017 10:44 14.7 161 SP-FCAB-3 599927 7564861 4268 02/02/2017 10:56 15.2 151 SP-FCAB-4 599914 7564899 4269 02/02/2017 11:02 15.4 106 SP-FCAB-5 599915 7564886 4275 02/02/2017 11:12 15.6 98 SP-FCAB-6 599954 7564869 4297 02/02/2017 11:19 15.1 131 SP-FCAB-7 599890 7564829 4272 02/02/2017 11:58 15.4 133 SP-FCAB-8 599893 7564824 4270 02/02/2017 12:10 16 122 SP-FCAB-9 599897 7564808 4257 02/02/2017 12:16 15.4 105 SP-FCAB-10 599874 7564755 4254 02/02/2017 12:35 15.9 125 SP-FCAB-11 599900 7564740 4268 02/02/2017 12:40 15.9 115 SP-FCAB-12 599927 7564737 4301 02/02/2017 12:48 15.2 124 SP-FCAB-13 599845 7564627 4242 02/02/2017 13:04 16.1 131 SP-FCAB-14 599802 7564619 4243 02/02/2017 13:24 15.9 122 SP-FCAB-15 599797 7564611 4240 02/02/2017 13:33 13.7 140 SP-FCAB-16 599785 7564605 4237 02/02/2017 13:40 14.7 137 SP-FCAB-17 599781 7564593 4238 02/02/2017 13:43 - - SP-FCAB-18 599765 7564582 4248 31/01/2017 17:10 15.6 220 SP-FCAB-19 599609 7564354 4256 31/01/2017 15:50 16.1 190 SP-FCAB-20 599617 7564357 4224 04/11/2016 15:54 - - SP-FCAB-21 599633 7564387 4221 04/11/2016 15:35 - - SP-FCAB-22 599638 7564396 4221 04/11/2016 15:33 - - SP-FCAB-23 599925 7564812 4251 31/01/2017 18:10 11.5 230 208
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Spring
name
X
(WGS84)
Y
(WGS84)
Altitude
(m.a.s.l.) Date Time Temperature
(°C)
Conductivity
(μS/cm)
SP-NN1 599919 7564845 4259 02/02/2017 11:43 14.1 111
SP-NN2 599895 7564799 4247 02/02/2017 12:24 16.1 118
SP-SI-1 599943 7564936 - 31/01/2017 16:18 15.2 170
SP-SI-5 597517 7564342 4165 01/02/2017 14:00 20.2 160
SP-SI-8 596886 7564854 4180 01/02/2017 11:15 19.2 88
SP-SI-9 597091 7564257 4138 01/02/2017 12:20 18.5 91
SP-SI-10 600098 7563292 - 01/02/2017 11:00 13.6 290
SP-SI-16 599927 7564885 4278 31/01/2017 18:30 15.5 84
SP-SI-17 599871 7564761 4279 31/01/2017 17:55 15.1 170
SP-SI-21 596867 7559405 - 21/12/2016 12:12 18.3 582
SP-SI-27 599611 7564360 4234 31/01/2017 15:30 16.6 220
SP-SI-29 598290 7563892 4165 01/02/2017 15:30 21.5 220
SP-SI-30 598354 7563875 4166 01/02/2017 15:51 19.5 200
SP-SI-31 596773 7563900 4059 02/02/2017 12:00 19.1 210
Table 5-8. Location and in-situ parameters of springs.
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111 5.10 Hydrochemical water sample collection A hydrochemical sampling campaign was carried out in December 2016 (base flow) and January-February 2017 (rainy season) so that chemical analysis might be carried out to characterize the surface, groundwaters and spring waters of the Silala River area. The locations of the sample stations as well as the type of analysis at each station were agreed among the hydrochemists (Prof. Christian Herrera and Prof. Ramón Aravena) responsible for their interpretation, Dr. Denis Peach and Arcadis. The sampling campaign involved 2 teams, from Arcadis and the Universidad Católica del Norte. The sample sets were analysed by the ALS laboratory in Antofagasta, the IT2 laboratory in Canada and University of Miami laboratories in the US. The complete sample set in each station included samples for 4 analytes: major ions, deuterium-oxygen 18 (2H-O18), enriched Tritium, and carbon-14 (C14). Sampling was carried out using the recommended methodologies found in the United States Geological Survey National Field Manual for the Collection of Water-Quality Data (USGS, 2015). In the baseflow campaign, water sample sets were taken at 15 stations, with a total of 15 sample sets, of which 2 were taken in the river, 2 in springs, and 11 in wells (Table 5-9). Their location can be seen in Figure 5-81. Major ions and deuterium-oxygen 18 were analysed in all the samples (Table 5-10). Enriched Tritium was analysed in spring sample SP-SI05-16, and groundwater samples PW-BO-B-16, PW-UQN-B-16, and PW-DQN-B-16. Carbon-14 was analysed in spring sample SP-SI05-16, and groundwater samples PW-BO-B-16 and PW-UQN-B-16. In the rainy season campaign, water sample sets were collected at 18 stations, with a total of 22 sample sets (including 2 duplicates and 2 blank samples). Of these 18, 4 correspond to the river, and 14 to springs. (Table 5-11). The duplicates were taken from river water. No groundwater samples were taken during the rainy season campaign. The sample locations can be seen in Figure 5-82. Major ions were analysed for all the samples (Table 5-12). Deuterium-oxygen 18 were analysed in all the samples, except for river samples R-SI-4-17, R-SI-6-17, R-SI-7-17, and R-SI-26-17, and Blank sample 2. Enriched Tritium and carbon-14 were analysed in spring samples SP-SI-8-17, SP-SI-10-17, and SP-SI-15-17. Carbon -14 was analysed for river sample R-SI-3-17. The results of the chemical analyses can be found in Herrera and Aravena (2017) and appended documents thereto. 210
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Sample
set
Sample
station
Coordinates WGS84,
19S
Date Time Sampling
UTM E depth (m) Class
(m)
UTM N
(m)
R-SI2-16 R-SI-02 600242 7565357 20/12/2016 15:20 - River
R-Río 1-16 R-Río 1 599410 7564117 21/12/2016 17:45 - River
SP-SI1-16 SP-SI-01 599943 7564936 20/12/2016 16:00 - Spring
SP-SI05-
16 SP-SI-05 597518 7564344 21/12/2016 15:15 - Spring
PW-DQNSI-
16
PWDQN
599090 7563871 21/12/2016 13:44 - Well
PW-BOA-
16 PW-BO 600185 7565278 21/12/2016 13:30 50 Groundwater
PW-BO-B-
16 PW-BO 600185 7565278 21/12/2016 15:30 75 Groundwater
CW-BOA-
16 CW-BO 600175 7565267 21/12/2016 15:55 55 Groundwater
CW-BOB-
16 CW-BO 600175 7565267 21/12/2016 16:25 110 Groundwater
PW-UQNA-
16
PWUQN
599346 7564063 21/12/2016 19:25 40 Groundwater
PW-UQNB-
16
PWUQN
599346 7564063 22/12/2016 11:00 75 Groundwater
MWLUQN-
A-16
MWLUQN
600175 7565267 22/12/2016 13:40 50 Groundwater
PW-DQNA-
16
PWDQN
598839 7563780 22/12/2016 18:15 45 Groundwater
PW-DQNB-
16
PWDQN
598839 7563780 22/12/2016 16:40 35 Groundwater
MWDQN-
A-16
MWDQN
598841 7563769 22/12/2016 19:20 35 Groundwater
Table 5-9. Location of sample stations where sample sets were collected during December 2016
(base flow).
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113 Sample set Sample station Major ions 2H/O18 Enriched3H C14 R-SI2-16 R-SI-02 x x R-Río 1-16 R-Río 1 x x SP-SI1-16 SP-SI-01 x x SP-SI05-16 SP-SI-05 x x x x PW-DQN-SI-16 PW-DQN x x PW-BO-A-16 PW-BO x x PW-BO-B-16 PW-BO x x x x CW-BO-A-16 CW-BO x x CW-BO-B-16 CW-BO x x PW-UQN-A-16 PW-UQN x x PW-UQN-B-16 PW-UQN x x x x MWL-UQN-A-16 MWL-UQN x x PW-DQN-A-16 PW-DQN x x PW-DQN-B-16 PW-DQN x x x MW-DQN-A-16 MW-DQN x x Table 5-10. Analytes within the sample sets collected during December 2016 (base flow). 212
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Sample set
Sample
station
Coordinates WGS84, 19S
Date Time Class
UTM E (m)
UTM N
(m)
R-SI-02 R-SI-2-17 600227 7565333 31/01/2017 15:24 River
R-SI-03 R-SI-3-17 599184 7563959 01/02/2017 17:20 River
R-SI-04 R-SI-4-17 597908 7564081 01/02/2017 13:30 River
R-SI-06 R-SI-6-17 597908 7564081 01/02/2017 13:40 River
R-SI-07 R-SI-7-17 596611 7563887 01/02/2017 17:19 River
R-SI-26
R-SI-26-
17 596611 7563887 01/02/2017 17:19 River
SP-SI-01 SP-SI-1-17 599956 7564952 31/01/2017 16:18 Spring
SP-SI-05 SP-SI-5-17 597517 7564342 01/02/2017 14:00 Spring
SP-SI-08 SP-SI-8-17 596886 7564854 01/02/2017 11:15 Spring
SP-SI-09 SP-SI-9-17 597091 7564257 01/02/2017 12:20 Spring
SP-SI-10
SP-SI-10-
17 600098 7563292 01/02/2017 11:00 Spring
SP-SI-15
SP-SI-15-
17 599926 7564847 31/01/2017 18:07 Spring
SP-SI-16
SP-SI-16-
17 599927 7564885 31/01/2017 18:30 Spring
SP-SI-17
SP-SI-17-
17 599871 7564761 31/01/2017 17:55 Spring
SP-SI-18
SP-SI-18-
17 599765 7564582 31/01/2017 17:10 Spring
SP-SI-19
SP-SI-19-
17 599609 7564354 31/01/2017 15:50 Spring
SP-SI-27
SP-SI-27-
17 599611 7564360 31/01/2017 15:30 Spring
SP-SI-28
SP-SI-28-
17 599825 7564812 31/01/2017 18:10 Spring
SP-SI-29
SP-SI-29-
17 598290 7563892 01/02/2017 15:30 Spring
SP-SI-31
SP-SI-31-
17 596773 7563900 02/02/2017 12:00 Spring
Blank Sample
Blank
Sample - - 01/02/2017 15:00 -
Blank Sample
2
Blank
Sample 2 - - 02/02/2017 19:39 -
Table 5-11. Location of sample stations where sample sets were collected during January-
February 2017 (rainy season).
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115 Sample set Sample station Major ions 2H/O18 Enriched3H C14 R-SI-02 R-SI-2-17 x x - - R-SI-03 R-SI-3-17 x x - x R-SI-04 R-SI-4-17 x - - - R-SI-06 R-SI-6-17 x - - - R-SI-07 R-SI-7-17 x - - - R-SI-26 R-SI-26-17 x - - - SP-SI-01 SP-SI-1-17 x x - - SP-SI-05 SP-SI-5-17 x x - - SP-SI-08 SP-SI-8-17 x x x x SP-SI-09 SP-SI-9-17 x x - - SP-SI-10 SP-SI-10-17 x x x x SP-SI-15 SP-SI-15-17 x x x x SP-SI-16 SP-SI-16-17 x x - - SP-SI-17 SP-SI-17-17 x x - - SP-SI-18 SP-SI-18-17 x x - - SP-SI-19 SP-SI-19-17 x x - - SP-SI-27 SP-SI-27-17 x x - - SP-SI-28 SP-SI-28-17 x x - - SP-SI-29 SP-SI-29-17 x x - - SP-SI-31 SP-SI-31-17 x x - - Blank Sample Blank Sample x x - - Blank Sample 2 Blank Sample 2 x - - - Table 5-12. Analytes within the sample sets collected during January-February 2017 (rainy season). 214
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Figure 5-81. Location of samples collected during the December 2016 campaign (base flow).
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117 Figure 5-82. Location of samples collected during the January-February 2017 campaign (rainy season). 5.11 Borehole fluid logging During December 2016, borehole fluid logging was carried out in 4 wells: PW-BO, CW-BO, PW-UQN and PW-DQN (Figure 5-83). The results are shown from Figure 5-84 to Figure 5-87. The parameters logged were temperature and electric conductivity. The interpretation of this work is presented in Appendix F. 216
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Figure 5-83. Location of wells with fluid logging.
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119 Figure 5-84. Temperature and Specific Conductivity in borehole PW-BO. 218
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Figure 5-85. Temperature and Specific Conductivity in borehole CW-BO.
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121 Figure 5-86. Temperature and Specific Conductivity in borehole PW-UQN. 220
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Figure 5-87. Temperature and Specific Conductivity in borehole PW-DQN.
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123 6 GEOLOGY AND HYDROGEOLOGY OF THE SILALA RIVER AND CATCHMENT In order to facilitate the spatial analysis of the data, the Silala River was divided into an upper course (from the international border to 1 km downstream of the junction with the Quebrada Negra) and a lower course (from 1 km downstream of the junction with the Quebrada Negra to the Inacaliri Police Station). Also, 4 analysis sites were designated along the course of the Silala ravine from east to west: (1) border (BO), (2) upstream of the Quebrada Negra UQN, (3) downstream of the Quebrada Negra DQN, and (4) Inacaliri Police Station PS (Figure 6-1). Figure 6-1. Study zones and analysis locations in the Silala River. 222
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6.1 Subsurface geology
The subsurface geology has been interpreted on the basis of the observed well
stratigraphy, in particular the core from CW-BO near the international border, and
electric resistivity tomography (ERT) and well logging. These data were analysed
separately and the loaded into the LeapFrog software, for 3-D analysis. This software
serves as tool for interpolation of surfaces based on points, lines and polygons. The grid
used for Leapfrog modelling was 20 m x 20 m x 20 m.
Among all the information listed above, well stratigraphy is the most reliable data, since
it is directly observed from drill cuttings or core. Also, well logs (gamma ray and
sometimes porosity) provided very useful data to verify the lithology changes observed
in the subsurface. Nevertheless, the interpretation of ERT data with resulting
“geoelectric units” showed good agreement with interpretations from other datasets.
Based on well log stratigraphy 3 geological units were identified from oldest to
youngest (Table 5-2, Table 5-3 and Figure 6-2):
1. Fluvial deposits
2. Silala Ignimbrite
3. Cabana Ignimbrite (base of this unit was not reached in the boreholes drilled)
Cross sections of the 3-D geological model (Figure 6-2) along the different study
locations show the spatial relationship between the geological units identified above
(Figure 6-3 to Figure 6-8). The location of each of these transects can be seen in Figure
6-3.
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125 Figure 6-2. 3-D model of the geology of the Silala River with well locations. View to the north. 224
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Figure 6-3. Location map of the cross sections in the study area.
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127 Figure 6-4. Cross section BO along the course of the Silala River. 226
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128 Figure 6-5. Cross section UQN along the course of the Silala River. Figure 6-6. Cross section DQN1 across the course of the Silala River. 128
Figure 6-5. Cross section UQN along the course of the Silala River.
Figure 6-6. Cross section DQN1 across the course of the Silala River.
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129Figure 6-7. Cross section DQN2 along the course of the Silala River. Figure 6-8.Cross section PS from Borehole EW-PS to PW-UQI. 129 Figure 6-7. Cross section DQN2 along the course ofthe Silala River.Figure 6-8.Cross section PS from Borehole EW-PS to PW-UQI.
228
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Fluvial deposits:
The fluvial deposits comprise an alternation of gravel and sandy gravel with minor silt
and clay (Hauser, 2004) with no consolidation. SERNAGEOMIN (2017) indicates that
the composition of the gravel portion corresponds mainly to sub-rounded to sub-angular
andesites and dacites. This geological unit is limited to the Silala River ravine.
The core from CW-BO shows coarse sand and boulder gravel, with gravel size up to 30
cm diameter (SERNAGEOMIN, 2017). The fluvial deposits reach a maximum
thickness of 18 m (well EW-PS) near the Silala River, with a mode around 6 m.
In the gamma-ray logs of wells PW-BO and PW-UQN this unit is characterised by high
gamma-ray values, ca. 70 API (Figure 5-26 and Figure 5-27), indicating the presence of
clay.
Figure 6-9. Core CW-BO in the fluvial deposits.
Silala Ignimbrite:
The Silala Ignimbrite is defined by SERNAGEOMIN as a sequence of welded tuffs of
andesitic composition that crop out along the course of the Silala River
(SERNAGEOMIN, 2017).
In the core of well CW-BO this deposit comprises a brown to orange and red lithic tuff
and scoria tuff (Figure 6-10 and SERNAGEOMIN, 2017).
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131 Figure 6-10. Core CW-BO of the Silala Ignimbrite and debris flow. A) Silala Ignimbrite with coarse clasts of scoria and andesite. B) Debris flow with a matrix of sand size. C) Enlarged view of the Silala Ignimbrite. D) Enlarged view of the debris flow with a sandy matrix. 230
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Drilling found the Silala Ignimbrite up to 59 m thick (well PW-BO) (Table 5-3 and
Figure 6-4). Its upper surface is found beneath the fluvial deposits between 5 and 13
m.b.g.l. (wells MW-BO and SPW-DQN respectively) (Table 5-3, Figure 6-4 and Figure
6-7) in the proximity of the river, whereas it was found at 27 m.b.g.l. in the upper
Quebrada Inacaliri (PW-UQI in Figure 6-8).
The formation tops recognized in borehole stratigraphy have been verified by
geophysical well logs, to within ±3 m. The gamma-ray logs of PW-BO (Figure 5-26)
and PW-UQN (Figure 5-27) show a distinct change from a zone above the Silala
Ignimbrite characterized by values ca. 70 API to a low gamma ray activity zone with
minimum of 28 API beneath this. This gamma ray activity change at the top of the
Silala Ignimbrite is coupled with a change in the porosity from values of -6 LPU above
the top in the fluvial deposits to values that reach a maximum of 90 LPU beneath this
well into the Silala Ignimbrite. The decrease in gamma-ray activity and increase in
porosity underneath the top of the Silala Ignimbrite indicates that the formation is low in
clay with significant porosity.
The core CW-BO description (SERNAGEOMIN, 2017) shows a great variability of
rock quality, with several zones of high density of fractures where the rock becomes
friable (8-19.2 m.b.g.l., 25.4-33.4 m.b.g.l.).
Cabana Ignimbrite:
The Cabana Ignimbrite is a crystal and ash rich tuff (SERNAGEOMIN, 2017).
Locally, in well CW-BO a 12.6 m thick (51.4 m.b.g.l. to 64.0 m.b.g.l.) coarse grained
sedimentary breccia is recognized underlying the base of the Silala Ignimbrite and
overlying the top of Cabana Ignimbrite (Figure 6-10). This is interpreted as a debris or
mud flow deposit (SERNAGEOMIN, 2017), indicating that the top of the Cabana
Ignimbrite was an exposed surface, subject to erosion and episodic fluvial deposition
within a former basin. For simplification of the stratigraphy, when 3-D modelling using
Leapfrog, the debris/mud flow deposit identified in well CW-BO has been incorporated
into the Silala Ignimbrite.
In the core of well CW-BO the Cabana Ignimbrite is a light brown to yellow crystal and
ash rich tuff (Figure 6-11, and SERNAGEOMIN, 2017). The Cabana Ignimbrite is
welded to poorly welded (SERNAGEOMIN, 2017). The lower part of the CW-BO core
has holes up to 5 cm across which probably correspond to pumice pieces that were
weathered. At 85 m deep, a 5 cm layer of fault gouge is found in the core.
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133 The Cabana Ignimbrite appears to be at least 129.5 m thick (PW-UQI in Table 5-4) in the area close to the Silala River (Figure 6-15) with at least 79.0 m thickness beneath the course of the Silala River (well EW-PS in Figure 6-8). A series of cross sections of the 3-D model, constrained by well log data (Figure 6-4 to Figure 6-8) show that the top of the Cabana Ignimbrite is found at 65 m.b.g.l. in the border location (BO) and it gradually becomes shallower until it crops out near the Inacaliri Police Station location (PS). Its base has not been recognized (Figure 6-4 to Figure 6-8 and SERNAGEOMIN, 2017). In the upper course of the Silala River (PW-BO and PW-UQN), the formation tops recognized in well stratigraphy are verified by the borehole geophysics, with an accuracy of ±3 m. The gamma-ray logs show a change from a zone above the top of the Cabana Ignimbrite to a zone beneath this. The zone above the top of the Cabana Ignimbrite is characterised in wells PW-BO (Figure 5-84) and PW-UQN (Figure 5-86) by gamma-ray values ca. 40 API. These values increase underneath the top of the Cabana Ignimbrite to 60-70 API. This change is probably related to a lithological change, where the Cabana Ignimbrite contains a higher proportion of secondary clay (not originally in the rock) compared to the formation above it. In the lower course of the Silala River (EW-PS), gamma-ray values in the Cabana Ignimbrite range from 50 API to 100 API, indicating greater secondary clay content (Figure 5-31). The secondary clay content in the Cabana Ignimbrite can be explained as a product of hydrothermal alteration of the minerals present in the ignimbrite (i.e. flow of groundwater at high temperature). Moreover, petrographic thin sections from surface samples taken and described by SERNAGEOMIN show a vitreous matrix with a texture that indicates presence of smectite, a hydrothermal alteration clay mineral (SERNAGEOMIN, 2017). The core CW-BO description (SERNAGEOMIN, 2017) shows a great variability of rock quality, with several zones of high density of fractures where the rock becomes friable. These intervals are: 58-61.3 m.b.g.l., 77.8-81.65 m.b.g.l., and 85.9-97.9 m.b.g.l.. The last interval is located underneath a fault gauge zone between 85.2 and 85.25 m.b.g.l., indicating that the friable nature of the rock could be related to a fault. 232
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Figure 6-11. Core CW-BO few meters above and below the contact between the debris/mud
flow (above) and Cabana Ignimbrite (below). A) Debris/mud flow. B) Cabana Ignimbrite. C)
Lower Cabana Ignimbrite with holes representing missing pumice.
C
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233
135 6.2 Aquifer parameters Between November 23rd and December 9th, pumping tests were performed in 2 purpose drilled boreholes, PW-BO and PW-UQN and a previously drilled hole PW-DQN. The full results and curve matches are found in Appendix B. All these wells penetrate fluvial deposits and Silala Ignimbrite and some of them also penetrate Cabana Ignimbrite. All the wells are screened through the Ignimbrites. Near the Inacaliri Police Station PS, in the lower course of the Silala River, where the Cabana Ignimbrite crops out, well EW-PS was drilled but not pump tested because it was virtually dry. Only after completion did a small amount of groundwater appear at the base of the well. The pumping and recovery tests in the upper course of the Silala River were carried out as described by Driscoll (1986), Fetter (1980) and Beale and Read (2013). The pumping and recovery tests in each of the study locations included a Step-Drawdown test (SDT) followed by a Constant-Rate Test (CRT). Details of the pumping tests can be found in Table 6-1. Pumping well Monitoring well Distance between wells Location Date of pumping initiation Date of last recovery measurement Discharge SDT (l/s) Discharge CRT (l/s) PW-BO CW-BO 15.7 Border (BO) 11/28/16 12/02/16 3-15 11 PW-UQN MWL-UQN 11.0 Upstream Q. Negra (UQN) 11/23/16 11/26/16 10-30 20 PW-DQN MW-DQN 11.0 Downstream Q. Negra (DQN) 12/06/16 12/09/16 15-30 20 Table 6-1. Pumping and recovery tests in the upper course of the Silala River. Step-Drawdown test and Constant-Rate tests with approximate duration of 24 hours were performed in each of the locations and the data collected was analysed using classical techniques. Step-Drawdown tests (SDT) were used to design the Constant-Rate tests (CRT) and to recognize type aquifer behaviors. The methods used to calculate aquifer parameters from CRTs and recovery tests were chosen according to the aquifer behavior seen in SDT at each location. According to this, Theis and Cooper-Jacob methods were used at all locations. The same methodology was applied when interpreting recovery tests. 234
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The methods described above require assumptions to be made that in this case are not
all met (e.g. full penetration of the aquifer). Therefore, aquifer parameter calculations
must be taken as indicative only. Also the drawdown curves as shown in Appendix B
indicate that the aquifer conditions are complicated by heterogeneity in both vertical and
horizontal directions, as is also indicated by simple inspection of the ignimbrite
deposits.
The resulting hydraulic parameters are presented in Table 6-2. The values of hydraulic
conductivity are in the range of 2.8 to 17 m/d. The higher values of this range were
calculated at BO location and are possibly related to the fact that the observation well
CW-BO was drilled 37 meters deeper than PW-BO, cross cutting a deeper zone of the
aquifer with different (higher) transmissivity (see Appendix B for more information). In
the deepest parts of CW-BO, friable ignimbrite with a high porosity was encountered
(see section 6.1 above).
Location Pumping
well
Monitoring
well Test Method T
(m2/d)
K
(m/d) S
Aquifer
saturated
thickness
(m)
BO PW-BO
PW-BO CRT Theis 450 8 - 57
PW-BO CRT Jacob 450 8 - 57
CW-BO CRT Theis 1087 12 2∙10-
4
93
CW-BO CRT Jacob 1087 12 2∙10-
4
93
PW-BO Recovery
test
Theis 1626 17 - 93
CW-BO Recovery
test
Theis 1177 13 - 93
UQN PW-UQN
MWL-UQN CRT Theis 241 4 1 10-
4
57
MWL-UQN CRT Cooper-
Jacob
247 4 1 10-
4
57
PW-UQN Recovery
test Theis 510 9 - 57
MWL-UQN Recovery
test Theisb 471 8 - 57
DQN PW-DQN
MW-DQN CRT Theis 130 3.6 3∙10-
3
36
MW-DQN CRT Cooper-
Jacob
130 3.6 3∙10-
3
36
PW-DQN Recovery
test Theis 107 3.0 - 36
MW-DQN Recovery
test Theisb 102 2.8 - 36
Table 6-2. Aquifer parameters in the study area.
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235
137 Figure 6-12 shows the log normal drawdown curve for (a) pumping and (b) observation wells for the pumping test at BO location. The behavior of the drawdown at the pumping well can be separated into two stages. The first one, for the first 90 minutes, and a second one after this period with different rate of drawdown. The observation well does not present a straightforward drawdown rate, but rather indicates the presence of a recharge boundary that reduces the drawdown rate over time. The parameters calculated are higher than the pumping well. These results indicate the highly complicated nature of the aquifer. Storage coefficient values found from the various analyses were between 1x10-4 and 3x10-3, which are typical values for confined aquifers (Todd, 1980). 236
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Figure 6-12. Aqtsolve analysis with Jacob method for (a) pumping well PW-BO and (b) monitoring well CW-BO.
a b
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139 6.3 Infiltration characteristics of the surface geologic units The infiltration tests have been analysed using standard techniques (SoilMoisture Equipment Corp., 2012) and permeability values have been estimated for different geologic units at outcrop (Appendix E). Among the non-consolidated to semi-consolidated deposits, alluvial and fluvial deposits seem to have the highest permeability values in the order of 1*10-1 m/d to 1 m/d (Table 6-3), as determined by double-ring infiltrometry. On the other hand, the pyroclastic fall deposits, composed mainly of weathered volcanic material (probably rich in clay) gave the lowest permeability value, in the order of 1*10-2 m/d. The rock units were tested using a Guelph permeameter, where incipient, ca. 15 cm thick, soil was developed. The permeabilities estimated ranged from ca. 1*10-2 m/d to 1 m/d (Table 6-4). The values are very variable and may represent local properties of a very heterogeneous thin soil covering a weakly permeable rock unit beneath. Point Ks (m/d) Geologic unit Lithology I-1 0.63 Alluvial deposits (Qal) Gravel, sand and silt I-2 (1) 1.94 Alluvial deposits (Qal) Gravel, sand and silt (Qal) I-2 (2) 2.05 Alluvial deposits (Qal) Gravel, sand and silt (Qal) I-3 0.02 Pyroclastic fall deposits (PIH(pc)) Weathered ash, scoria and pumice I7 0.19 Fluvial deposits (Qf) Gravel, sand and silt I-8 0.29 Fluvial deposits (Qf) Gravel, sand and silt (Qf) Table 6-3. Permeability of surface geologic units based on double ring method. 238
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Point Ks (m/d) Geologic unit Lithology
I-4 1.61
Miocene-Pliocene lavas
(MsPvd)
Thin, 15 cm thick incipient soil cover
(fractured and weathered rock)
I-5 0.03
Miocene-Pliocene lavas
(MsPvd)
Thin, 15 cm thick incipient soil cover
(fractured and weathered rock)
I-6 0.48 Ignimbrite Cabana (Piic)
Thin, 15 cm thick incipient soil cover
(fractured and weathered rock)
I-9 0.37 Ignimbrite Silala (Pliis)
Thin, 15 cm thick incipient soil cover
(fractured and weathered rock)
I-10 0.93 Pleistocene lavas (Pliv(a))
Thin, 15 cm thick incipient soil cover
(fractured and weathered rock)
Table 6-4. Permeability of surface geologic units based on Guelph permeameter method.
6.4 Hydrogeological units
Based on surface geology, subsurface geology, aquifer parameters and permeability of
surface geologic units, six hydrogeological units have been identified: HU1 (Fluvial
deposits), HU2 (Alluvial deposits), HU3 (Ignimbrite), HU4 (Pyroclastic fall deposits),
HU5 (Andesitic and dacitic volcanic rocks) and HU6 (Weakly permeable rock). The
spatial distribution of these units can be observed in the hydrogeological map (Figure
6-13). Cross sections in each study location are shown in Figure 6-14 (BO location),
Figure 6-15 (UQN location), Figure 6-16 (DQN location), Figure 6-17 (DQN location)
and Figure 6-18 (PS location).
HU1: Fluvial deposits
HU1 comprises sandy gravel to gravel rich sands, with some clay content. Gravel size
ranges from few centimetres to several tens of centimetres. The fluvial deposits reach a
maximum thickness of 18 m in well EW-PS near the Silala River, with a mode of about
6 m. This unit is located along the Silala River ravine and has an elongated and narrow
shape in plan view, with a mean width of approximately 20 m (Figure 6-13 and Figure
6-16).
During the months of November and December in the dry season (base flow), HU1 was
found to be saturated just beneath the surface water in the Silala River at four points
along a ~2-km reach of the river, beginning near the Chile-Bolivia international border
and finishing downstream of the confluence of the Silala River and Quebrada Negra
(Suárez et al., 2017). The shallow wells that were drilled on the sides of the river (MWBO
and MWS-UQN), with screens in this unit, were initially dry. After some days, a
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141 water level could be measured, very close to the base of the screened interval or below the screened interval. This water level was constant over time, probably representing locally saturated zones within HU1. HU1 can be classified as an unconfined aquifer, but since a groundwater level was difficult to detect it would appear that this aquifer is only intermittently saturated along the length of the river. Suárez et al. (2017) found at four points along the river that a groundwater head could be measured in the metre of sediments immediately beneath the river bed. It would appear therefore that the vertical heterogeneity of the sediments may be great and may lead to the river being perched in some places above the lower fluvial sediments. Temperature studies along a 1.3 km length of the river (Suárez et al., 2017) indicate also that there are inflows to the river from springs often emanating from the walls of the ravine which appear to contribute groundwater to the river. Permeability data from surface infiltration tests indicate values in the order of 1*10-1 m/d. HU2: Alluvial deposits As defined by SERNAGEOMIN, 2017, these deposits are poorly consolidated and range from volcanic blocks to gravel, sand and silt. These are mainly exposed in a planar surface to the north and south of the Silala River ravine. Interpretation of the stratigraphy of well PW-UQI shows this alluvium to be at least 26 m thick at this site but it pinches out towards the south (Figure 6-18). The ERT geophysics shows localized high conductivity anomalies, within this unit. These anomalies are elongated parallel to its base (tabular shape), and are found between some 5 m to 20 m.b.g.l. (Figure 6-19). These anomalies are interpreted as saturated sediments forming a shallow perched aquifer. There are at least 34 springs that appear along the wall of the Silala ravine at both high and low levels, and many minor drainage channels lateral to the river that can be observed along the Silala ravine. These are interpreted as being supplied by recharge to HU2 which hosts a perched aquifer(s) with groundwater flow directions towards the Silala ravine or the minor lateral drainage channels. ERT geophysics profile L6 (part 6), about 300 m NW of the zone where most of the springs were found, shows discrete tabular high conductivity units within the uppermost 10 m, which are interpreted as a perched aquifer (Figure 6-19). Infiltration tests indicate high infiltration capacity, with values that range from the order of 5*10-1 m/d to 2 m/d. 240
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HU3: Ignimbrite
HU3 comprises two separate geological ignimbrite flow units: Cabana Ignimbrite and
Silala Ignimbrite. Thus, HU3 could perhaps be divided into a lower unit composed of
crystal rich tuff and an upper unit composed of welded lithic tuff. The log of the core of
well CW-BO (SERNAGEOMIN, 2017) shows that the rock quality is very
heterogeneous, with zones of fractures/faults and zones that are strongly weathered and
where the ignimbrite is very friable.
HU3 crops out in the walls of the Silala River ravine. Under the course of the Silala
River, below the fluvial deposits (HU1), its eroded top is up to 13 m.b.g.l. (well SPWDQN)
whereas its base is not recognized (Figure 6-17 and Table 5-3).
All the boreholes drilled for this project deeper than 40 metres penetrated HU3 and
found water in sufficient quantities to be pumped, except for EW-PS which was dry
after the final airlift. The first water strike in each well was initially between 10 m.b.g.l.
to 15 m.b.g.l.. The groundwater rose up the borehole to a level of between 8 and 9
m.b.g.l., so HU3 can be interpreted as a deep confined or semi-confined aquifer, since
its groundwater is under pressure.
The confined nature of HU3 is also shown by the presence of the artesian well SPWDQN.
This well discharges water directly into the Silala River, with an estimated
discharge of about 90 l/s (Suárez et al., 2017). The other wells within 200 metres of
SPW-DQN (PW-DQN and MW-DQN) do not show the artesian behaviour of SPWDQN.
Storage coefficient values calculated from pumping tests also indicate the confined
nature of the aquifer. The calculated values of permeability range from 3 to 9 m/d.
Pumping and recovery test analysis in the border location BO indicated the presence of
a very productive interval in the Cabana Ignimbrite, in a zone of friable rock interpreted
from the core of CW-BO. The pumping well demonstrated a very rapid large drawdown
and very rapid recovery, indicative of high well losses and low transmissivity. It is
thought that the source of groundwater pumped from PW-BO may well come via CWBO
from a deeper high transmissivity zone penetrated by this cored monitoring
borehole.
Permeability data from surface infiltrations tests in the thin soil unit developed in HU3
indicate permeability around 0.4-0.5 m/d.
The ERT geophysics revealed localized high conductivity anomalies, within HU3.
These anomalies have a very irregular shape, and in the zone where the wells are
drilled, along the Silala River ravine, the top of the high conductivity zones fits well
with the lithology change from fluvial deposits above to saturated ignimbrite underneath
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143 (Figure 6-20 and Appendix C). These anomalies can be found mainly underneath the course of the Silala ravine, from 1 km west of the junction with the Quebrada Negra to the border (ca. 3 km long zone) about 10 m.b.g.l. North and South of the Silala ravine, these anomalies are either found deeper (below 50 m.b.g.l.) or are not found. These anomalies are interpreted as saturated ignimbrite with significant storage and transmissivity. West of this zone, close to the Inacaliri Police Station, where Cabana Ignimbrite crops out and well EW-PS was drilled, irregular anomalies were found at or near the surface. These are interpreted as saturated low conductivity ignimbrite (with low permeability as described above and in Appendix C). HU4: Pyroclastic fall deposits HU4 corresponds to pyroclastic fall deposits described by SERNAGEOMIN (2017) as well stratified, unconsolidated deposits, located in the central south part of the study area (Figure 6-13 and Figure 6-16). They comprise alternating dark scoria and subordinated pumice, within an ash matrix. These deposits are very weathered in surface, and may be up to 20-30 m thick (Nicolás Blanco, personal communication, 2017). Permeability data from surface infiltrations tests indicate a low permeability of 0.02 m/d. HU5: Andesitic and dacitic volcanic rocks HU5 comprises Volcanic Sequences from the Lower Pleistocene (Pliv(a)), mainly andesitic and dacitic volcanic rocks, made up of lavas, agglomerates and andesitic tuffs (SERNAGEOMIN, 2017). These deposits occur in the highest parts of the Silala basin, where Cerro Inacaliri and Volcán Apagado are developed, and also in large areas near the headwaters of the Silala River. HU5, where lava has extruded from the (then) Inacaliri volcano at about 1.5 Ma, is likely to have significant aquifer characteristics, in terms of permeability, as these are sub-aerial lava flows, probably highly porous and weathered. Hauser (2004) indicated that some of the Orientales wetland springs appear to emerge from them, so for the purposes of the conceptual understanding they should be considered separately from HU6. They form m.a.s.l.sive and extensive lava flows that converge toward the shallow depression of the Orientales wetlands and are likely to provide recharge areas for the wetland springs. There is uncertainty about their importance since they only occur in Bolivian territory and no data or studies of their hydrogeology are available. 242
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Permeability data from surface infiltrations tests indicate permeability of 0.92 m/d.
HU6: Weakly permeable rocks
HU6 comprises all the other rocks that crop out in the Silala River basin (Figure 6-13),
mainly Miocene-Pliocene Volcanic Sequences and minor glacial deposits. Miocene-
Pliocene Volcanic Sequences correspond to dacites which develop a thin, 15 cm thick
incipient soil, weathered layer in the surface. Underneath this, very low permeability
rock is found. The glacial deposits correspond to poorly sorted, unconsolidated blocks,
gravel, sand, silt and clay (SERNAGEOMIN, 2017) and are probably low permeability
also.
Permeability data from surface infiltrations tests in the thin soil unit developed in
Miocene-Pliocene Volcanic Sequences indicate permeability ranging from ca. 1*10-2
m/d to 1 m/d.
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145 Figure 6-13. Hydrogeological map of part of the study area. 244
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Figure 6-14. Hydrogeological cross section in BO location.
Figure 6-15. Hydrogeological cross section in UQN location.
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147 Figure 6-16. Hydrogeological cross section in DQN1 location. Figure 6-17. Hydrogeological cross section in DQN2 location. 246
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Figure 6-18. Hydrogeological cross section in PS location.
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149 Figure 6-19. ERT geophysics transect L6 (part 6), in the alluvial plain north of the Silala River (oriented NE-SW, between 500 m to 1300 m from the Chile-Bolivia boundary, about 300 m NW of the zone of the ravine where most of the springs where surveyed). Dotted line marks the boundary between different geoelectric units. In the uppermost 10 m (HU1), several discrete high conductivity tabular units can be identified. See Appendix C for more details. 248
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Figure 6-20. ERT geophysics transect L2, oriented NS, including DQN location, where well PQ-UQN was drilled. Dotted line marks the
boundary between a high resistivity zone above and a lower resistivity zone below. Underneath the Silala ravine, localized high conductivity
anomalies, within HU3 can be found. See Appendix C for more details.
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151 6.5 Water level analysis Water levels were analysed in space (areal distribution of water levels for a chosen date) and over time for the ignimbrite aquifer (HU3). The fluvial aquifer (HU1) was not analysed, since it did not have a saturated depth during the observation period in the monitoring wells constructed. 6.5.1 Water level map Water level data from six boreholes on 13 December 2016 was used for this. These are shown in Table 6-5 and on Figure 6-21. ID Coordinates WGS84, 19S Surface elevation (m.a.s.l.) Date Water level (m.b.g.l.) Stick up (m) Water level (m.a.s.l.) Classification E N PW-BO 600185 7565278 4272.6 13/12/2016 8.4 0.8 4264.9 Well PW-UQN 599346 7564063 4204.6 13/12/2016 9.1 0.5 4196.0 Well MWL-UQN 599353 7564072 4205.1 13/12/2016 9.8 0.7 4196.0 Well CW-BO 600175 7565267 4272.6 13/12/2016 6.9 0.6 4266.3 Well PW-DQN 598839 7563780 4178.5 13/12/2016 2.8 0.3 4176.0 Well MW-DQN 598841 7563769 4179.4 13/12/2016 4.2 0.9 4176.1 Well Table 6-5. Water level data used for water level analysis. Using the water level values measured in the ignimbrite aquifer (beneath the Silala River) a groundwater gradient was calculated along 2 sections. Between the BO location and UQN location a groundwater gradient of about 0.05 was calculated, whereas between UQN and DQN the calculated value was about 0.03. The gradient of the river (using Arcadis DTMtopography and the corresponding distance between the points) shows the same value seen between the BO and UQN locations (0.05) and a value slightly higher (0.04) in the section between UQN and DQN compared to the groundwater gradient (0.03). The water levels measured clearly indicate that the water within the ignimbrite aquifer flows from the border (northeast) to the southwest, following the same sense and direction of surface flow of the Silala River (Figure 6-21). 250
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Figure 6-21. Water level map in the ignimbrite aquifer, underneath the Silala River.
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153 6.5.2 Water level time series analysis A time series analysis of water levels has been carried out for the boreholes drilled at the international border (BO), upstream of the junction with the Quebrada Negra (UQN) and downstream of the junction with the Quebrada Negra (DQN). Silala ravine at the international border The water level in the ignimbrite aquifer is located ca. 20 m above the top of the screened well interval in well PW-BO as well as in CW-BO. In the case of well MW-BO, the water level is 4 m below the base of the screen. Therefore, this water is not representative of the fluvial aquifer and is not interpreted. It is also important to note that the water level in well CW-BO is ca. 1 m higher than the water level in well PW-BO (Figure 6-22). This almost certainly reflects the greater depth of the borehole and is a response to a high head found towards the base of the borehole. Wells CW-BO and PW-BO show a similar water level time series from the beginning of measurements to November 27th: a peak water level followed by a decrease of 1 m (Figure 6-22). After November 27th, the water level decreases by almost 0.5 m in well PW-BO, recovers later after December 10th and seems to be stable until the last measurements in February. On the other hand, well CW-BO shows no decrease after November 27th, but remains very stable until the last measurements in February. The water level decrease after November 27th (until December 1st) was probably caused by the pumping and recovery tests performed between November 28th and December 2nd. After the tests ceased, 15 days later, a 0.5 m water level recovery was seen. Well CW-BO was much less affected by the pumping, and the piezometric level is controlled from depths below the base of PW-BO. The slow recovery in the pumped well is indicative of the low transmissivity and storage of the rocks that the well was drilled into, whereas the cored borehole suffered minimal effects of the pumping. The stable water levels in both wells from mid-December to mid-February indicate that the water levels were not affected by the precipitation that started in January. 252
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Figure 6-22. Enlarged view of time-series of water level in wells in the border zone (PW-BO,
MW-BO and CW-BO).
Silala ravine upstream of the junction with Quebrada Negra
The water level in the ignimbrite aquifer is located more than 15 m above the top of the
screened well interval in well PW-UQN, as well as in MWS-UQN.
In the case of well MWS-UQN, the water level is just at the base of the screened
interval. Therefore, there is some doubt about the quality of this data, and it may not be
representative of the fluvial aquifer water level.
Wells PW-UQN and MWS-UQN show a similar water level time series from the
beginning of the monitoring period (November), when the water level in well MWLUQN
was ca. 0.5 m higher than the water level in well PW-UQN (Figure 6-23). It can
be seen that an initial stable stage of high water level was followed by a 1 m decrease on
December 1st. After December 1st, the water level in well MWL-UQN remained
constant, whereas in PW-UQN it rose to the same level as that of well MWL-UQN.
After this date, the water level in both wells was very stable until the last measurements
in mid-February.
The water level fall detected on December 1st is probably related to the pumping and
recovery tests performed in PW-UQN between November 23rd and November 26th. The
4260
4262
4264
4266
4268
4270
water level (masl)
CW-BO MW-BO PW-BO
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155 later rise of the water level in PW-UQN to a water level identical to well MWL-UQN could be related to the fact that these wells became directly connected in the subsurface during drilling of well MWL-UQN, probably due to a collapse of the friable ignimbrite underneath. The stable water levels in both wells from mid-December to mid-February show that the water level was not affected by the summer precipitation. Figure 6-23. Enlarged view of groundwater level time series in wells in the Silala ravine upstream of the junction with Quebrada Negra (PW-UQN, MWS-UQN and MWL-UQN). Silala ravine downstream of the junction with Quebrada Negra The water level in the ignimbrite aquifer is located more than 4 m above the top of the screened well interval in well PW-DQN and 15 m above the top of the screened well interval in well MW-DQN. The water levels in both wells are very similar, and one plots on top of the other. They are relatively stable (Figure 6-24), showing a one metre increase from the first monitoring point. After this, the water level in both wells showed to be very stable until last measurements in early February. 419041924194419641984200water leve (
masl)PW-UQNMWS-UQNMWL-UQN 254
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The stable water levels in both wells from mid-December to early February show that
the water level does not appear to be affected by precipitation that fell between January
and February.
Figure 6-24. Enlarged view groundwater level time series in wells in the Silala ravine
downstream of the junction with Quebrada Negra (PW-DQN and MW-DQN).
6.6 Hydrochemistry
This chapter is a summary of the work of Herrera and Aravena (2017) who interpreted
the entire chemical and isotope data.
Location maps for the base flow campaign samples (December 2016) and rainy season
campaign samples (January-February 2017) can be seen in Figure 5-81 and Figure 5-82.
The hydrochemistry data (major ions) and environmental isotopes data are interpreted
separately below. Environmental isotopes include deuterium-oxygen 18, enriched
Tritium, and Carbon-14 data. The geochemistry section presents an analysis of the in
situ salinity and patterns of major ion variation found in the different waters analysed.
The Deuterium-oxygen 18 data are used to identify isotopic signatures of the different
waters and their relationship with local and regional recharge areas. The enriched
Tritium and Carbon-14 data are used as tracers for the understanding of river-aquifer
4170
4172
4174
4176
4178
4180
water level (masl)
PW-DQN MW-DQN
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157 interactions. For methodology and background of the different analytical methods see Herrera and Aravena (2017). 6.6.1 Geochemistry data The field parameters and hydrochemical data for the base flow and rainy season campaigns are shown in Table 6-6 and Table 6-7 respectively. The waters analysed can be subdivided in terms of electric conductivity (EC) into 2 groups: (1) very low conductivity and (2) low conductivity. The first group comprises river and spring waters, which have conductivity values ranging between 88 and 260 μS/cm (Table 6-6 and Table 6-7). The second group corresponds to groundwaters with conductivity values ranging from 255 to 382 μS/cm. The first group can be further subdivided in terms of mineralization into higher and lower groups. The lower mineralization group comprises spring waters sampled from the northern side of the lower course of the Silala River (sample stations SP-SI-5, SP-SI-8, and SP-SI-9) (Figure 5-81 and Figure 5-82). This subgroup is characterized by EC values between 88 and 95 μS/cm (Table 6-6 and Table 6-7). These values are very low for groundwater and indicate a very low level of total dissolved solids. 256
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Sample Set Water type T°C pH lab
EC lab Alkalinity Cl SO4 HCO3 Ca Mg K Si Na NO3
(μS/cm) (mg/l of CaCO3) mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L
R-SI2-16 River 17.5 8.67 204.8 91 2.34 5.92 91.622 9.90 4.099 2.500 18.80 19.74 0.19
R-Río 1-16 River 14.5 8.09 175.7 104 4.55 7.40 93.818 9.80 4.014 2.780 21.90 18.07 0.25
SP-SI1-16 Spring 15.2 7.76 189.7 77 2.13 6.11 92.72 10.34 4.293 2.960 22.00 16.75 0.33
SP-SI05-16 Spring 20.3 7.01 88,3 25 1.28 8.26 30.378 3.93 0.646 2.910 21.40 10.37 0.27
PW-DQN-SI-16 Groundwater 20.7 7.58 315 150 1.86 9.80 170.312 21.89 10.300 5.070 30.70 21.09 0.32
PW-BO-A-16 Groundwater 18.9 7.80 382 5.86 9.80 206.912 24.99 13.900 5.110 29.30 26.70 0.35
PW-BO-B-16 Groundwater 17.7 7.38 354 152 5.36 11.03 201.178 24.90 12.700 4.990 28.00 24.79 0.30
CW-BO-A-16 Groundwater 16.9 7.53 356 148 7.29 13.69 181.78 21.57 11.890 4.900 29.60 26.12 0.58
CW-BO-B-16 Groundwater 16 7.49 345 147 6.48 17.13 179.218 22.09 11.660 4.810 29.10 26.51 0.56
PW-UQN-A-16 Groundwater 19.4 7.48 321 147 2.19 10.35 183.854 23.11 10.470 5.610 32.80 21.97 0.28
PW-UQN-B-16 Groundwater 20.1 7.56 327 168 4.65 11.33 187.514 22.99 10.440 5.550 32.20 21.73 0.31
MWL-UQN-A-16 Groundwater 20.3 7.46 319 110 5.35 11.57 181.78 22.69 10.020 5.390 32.10 21.31 0.31
PW-DQN-A-16 Groundwater 17.4 7.47 255.6 3.50 17.75 128.344 16.32 7.567 4.160 25.80 21.12 0.31
PW-DQN-B-16 Groundwater 17.7 7.34 262.3 102 3.39 19.00 129.93 16.45 7.302 4.230 27.20 20.50 0.29
MW-DQN-A-16 Groundwater 19.5 7.41 288.3 137 2.58 11.73 167.14 20.93 9.243 5.220 28.50 22.06 0.29
Table 6-6. In situ parameters and major ions for base flow (December, 2016). From Herrera and Aravena (2017).
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159 The higher mineralization group comprises river water (sample stations R-SI2, R-SI3, R-SI4, R-SI7 and R-Rio1 with EC between 175- 260 μS/cm), springs located in the upper course of the Silala River (sample station SP-SI1 among others along the Silala ravine and SP-SI-10 in the Quebrada Negra), and springs located in the southern lower course of the Silala River (sample stations SP-SI29 and SP-SI-31) (Figure 5-81 and Figure 5-82). Both sets of spring locations have EC values between 136-228 μS/cm (Table 6-6 and Table 6-7). The Silala River and the spring waters are mainly Sodium Bicarbonate type water with relatively high content of Ca (Figure 6-25 and Figure 6-26). As can be seen from the Stiff diagrams, no significant differences are observed between the springs located in the upper and lower part of the river course (Figure 6-25 and Figure 6-26). The groundwaters have a distinctly different major ion chemistry to the spring and river waters and are Calcium Bicarbonate type water, (Figure 6-25). In conclusion, EC and major ions data show that the spring waters from the northern side of the lower course of the river are recharged very locally since they have such a low degree of mineralization. But the spring and river waters have a different chemical fingerprint from the groundwaters. It seems likely that these springs are discharging from a perched aquifer in the alluvial deposits (HU2). Clearly the spring and river waters are related since the one drains into the other. The chemical data indicate that the perched aquifer does not interact with the ignimbrite aquifer (HU3) from which the groundwater samples were collected. 258
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Sample Set Water
type
T
°C
p
H
la
b
EC lab
(μS/cm)
Alkalinit
y
(mg/l of
CaCO3)
Cl
mg/
L
SO4
mg/
L
HCO
3
mg/L
Ca
mg/L
Mg
mg/L
K
mg/L
Si
mg/L
Na
mg/L
NO3
mg/
L
R-SI-2-17 River 17.1 8.6 186.7 66 2.36 6.27 95.6 8.37 3.633 2.010 22.10 17.44 0.22
R-SI-3-17 River 18.3 7.9 181.3 22 2.31 6.48 91.6 9.29 3.664 2.440 19.80 16.56 0.23
R-SI-4-17 River 20.8 8.6 260.3 96 1.99 7.89 133 16.04 7.164 3.740 25.90 18.39 0.24
R-SI-7-17 River 18.4 8.7 243.9 119 1.92 9.33 115 14.42 6.407 3.550 25.30 17.16 0.19
SP-SI-1-17 Spring 15.2 7.6 182.9 63 2.12 6.64 100 9.96 4.106 2.710 21.70 15.97 0.35
SP-SI-5-17 Spring 20.2 7.8 88.2 48 1.24 8.19 34 3.79 0.563 2.570 21.90 9.41 0.29
SP-SI-8-17 Spring 19.2 7.2 95.3 25 1.18 11.50 31 3.95 0.489 2.250 20.40 10.66 0.24
SP-SI-9-17 Spring 18.5 7.2 92.1 64 1.09 9.72 32 4.24 0.525 2.580 21.10 9.77 0.21
SP-SI-10-17 Spring 13.6 7.9 228.4 74 2.16 14.88 99 14.63 6.294 6.680 30.60 11.86 0.22
SP-SI-15-17 Spring 15.6 7.9 161.2 43 2.09 6.24 76 8.45 3.090 2.360 19.70 14.88 0.35
SP-SI-16-17 Spring 15.5 7.9 150.9 48 2.09 5.94 73 7.06 2.550 2.040 23.00 13.52 0.36
SP-SI-17-17 Spring 15.1 7.9 136.5 28 2.06 5.81 68 6.54 2.119 2.120 18.60 13.66 0.34
SP-SI-18-17 Spring 15.6 7.8 140.4 19 2.06 6.08 62 6.12 2.175 1.960 22.90 12.91 0.34
SP-SI-19-17 Spring 16.1 7.8 139.8 28 2.04 5.94 66 6.60 2.463 2.060 19.60 13.35 0.34
SP-SI-27-17 Spring 16.6 7.8 158.7 83 2.03 6.52 74 7.66 3.107 2.180 23.80 14.02 0.33
SP-SI-28-17 Spring 11.5 7.6 176.3 17 2.13 7.10 87 9.60 3.908 2.630 22.00 15.45 0.34
SP-SI-29-17 Spring 21.5 7.6 167.3 44 2.01 6.28 78 8.59 2.762 2.810 19.60 14.81 0.31
SP-SI-31-17 Spring 19.1 7.9 192.7 75 2.32 6.55 82 8.73 2.907 3.710 26.60 16.17 0.44
Table 6-7. Insitu parameters and major ions for rainy season (January-February, 2017). From Herrera and Aravena (2017).
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161 Figure 6-25. The Stiff diagrams of water samples collected during the base flow (December, 2016). Taken from Herrera and Aravena (2017). 260
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Figure 6-26. The Stiff diagrams of water samples collected during the rainy season (January-
February, 2017). Taken from Herrera and Aravena (2017).
6.6.2 Environmental isotope data
6.6.2.1 Deuterium-oxygen 18 data
The deuterium-oxygen 18 stable isotopes data for the river, springs and groundwater
collected for the base flow and rainy season campaigns are reported in Table 6-8. These
data have been plotted and compared with the global meteoric water line (GML) (δ2H =
8δ18O + 10) and the local meteoric water line (LML) (δ2H = 7,9δ18O + 14) (Figure
6-27a for base flow and Figure 6-27b for rainy season) (see Herrera and Aravena (2017)
for more detail).
Figure 6-27 shows that the stable isotope data can be grouped as follows: (1) isotope
values close to the LML or between the LML and the GML with higher deuterium
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163 excess values (around 15 ‰) and (2) isotope values below the GML. The water in the first group corresponds to springs in the northern lower course of the Silala River. Samples in the second group correspond to springs in the southern lower course of the Silala River, springs in the upper course of the river, river water and groundwater. This pattern is seen in the base flow campaign as well as in the rainy season campaign (Figure 6-27a and Figure 6-27b respectively). Based on the isotope data, the springs in the northern part of the lower course of the river should represent local recharge. Sample ID Water type δ18O VSMOW (‰) δ2H VSMOW (‰) R-SI-02-16 River -11.5 -92 R-Río 1-16 River -11.5 -91 SP-SI-01-16 Spring -11.7 -92 SP-SI-21-16 Spring -11 -82 SP-SI-05-16 Spring -11.5 -83 PW-DQN-SI-16 Well -11.9 -93 PW-BO-A-16 Groundwater -11.9 -94 PW-BO-B-16 Groundwater -11.9 -93 CW-BO-A-16 Groundwater -11.9 -94 CW-BO-B-16 Groundwater -11.9 -94 PW-UQN-A-16 Groundwater -12 -93 PW-UQN-B-16 Groundwater -11.9 -93 MWL-UQN-A-16 Groundwater -11.9 -93 PW-DQN-A-16 Groundwater -11.7 -92 PW-DQN-B-16 Groundwater -11.8 -92 MWL-DQN-A-16 Groundwater -11.9 -93 Table 6-8. Deuterium-oxygen 18 data of water samples collected during the base flow (December, 2016). Taken from Herrera and Aravena (2017). 262
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Sample ID Water type δ18O VSMOW (‰) δ2H VSMOW (‰)
R-SI-2-17 River -11.6 -93
R-SI-3-17 River -11.6 -92
SP-SI-1-17 Spring -11.8 -93
SP-SI-5-17 Spring -11.7 -83
SP-SI-8-17 Spring -12 -84
SP-SI-9-17 Spring -12 -84
SP-SI-10-17 Spring -11.7 -90
SP-SI-15-17 Spring -11.8 -92
SP-SI-16-17 Spring -11.8 -92
SP-SI-17-17 Spring -11.8 -92
SP-SI-18-17 Spring -11.8 -92
SP-SI-19-17 Spring -11.8 -92
SP-SI-27-17 Spring -11.8 -92
SP-SI-28-17 Spring -11.8 -92
SP-SI-29-17 Spring -11.7 -91
SP-SI-31-17 Spring -11.7 -90
Table 6-9. Deuterium-oxygen 18 data of water samples collected during the rainy season
(January-February, 2017). Taken from Herrera and Aravena (2017).
On the other hand, the isotopic fingerprint for springs in the southern lower course of
the Silala River, springs in the upper course of the river, river water and groundwater
suggests that all these waters are associated with recharge areas at similar altitudes.
Herrera and Aravena (2017) indicate that: “The isotope composition of these waters all
plotted below the local meteoric water line, which is a typical feature for groundwater
and springs in Northern Chile (Fritz et al., 1981; Magaritz et al., 1989; Uribe et al.,
2015). This pattern has been associated with evaporation during the waters’ residence
time in the unsaturated zone (Magaritz et al., 1989). Therefore, assuming a slope of 3
for the evaporation line in soil (Clark and Fritz, 1997) and extrapolating the data using
this slope, the evaporation line would intersect the local meteoric water line around -
14,5 ‰ of δ18O, which is within the range of isotope values measured for precipitation
above 3,500 m.a.s.l (Aravena et al., 1999, Uribe et al., 2015)”. Therefore, it can be
inferred that the water in this group may be representative of a more regional flow
system recharged in the high Andes.
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165 Figure 6-27. a) Plot of δ18O and δ2H for river, spring water, and wells (base flow) b) Plot of δ18O and δ2H of river and spring water (rainy season). LML: Local meteoric line. GML: Global Meteoric Line. The solid black line represents an evaporation line with slope of 3 in both cases. a) b) 264
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6.6.2.2 Enriched Tritium data
The tritium input function for the southern Hemisphere, showing the concentration of
tritium in rainwater since 1958 (right after thermonuclear tests were initiated in the
atmosphere) is presented in Figure 6-28. Based on this figure the tritium data for recent
precipitation in the study area should be between 3 and 5 TU.
Figure 6-28. Concentrations of monthly rainwater tritium measured at IAEA stations in the
Southern Hemisphere in South America (Herrera et al., 2006).
1957
1959
1961
1963
1965
1967
1969
1971
1973
1975
1977
1979
1981
1983
1985
1987
1989
1991
1993
1995
1997
1999
2001
2003
0
10
20
30
40
50
60
70
80
90
100
Porto Alegre
Cuzco
Salta
Los Molinos
La Paz
Leyenda
TRITIO (UT)
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167 Table 6-10 shows that springs, river water and groundwater contain very little tritium. Sample ID Collection date TU Water type ± 1σ PW-BO-B-16 21-12-2016 <0.05 Groundwater 0.23 PW-UQN-B-16 22-12-2016 0.07 Groundwater 0.23 PW-DQN-B-16 22-12-2016 0.22 Groundwater 0.23 R-SI-02-16 20-12-2016 0.16 River 0.23 SP-SI-21-16 21-12-2016 0.18 Spring 0.22 SP-SI-05-16 21-12-2016 < 0.05 Spring 0.19 SP‐SI‐8‐17 02-01-2017 < 0.05 Spring 0.20 SP‐SI‐15‐17 31-01-2017 0.31 Spring 0.29 SP‐SI‐10‐17 02-01-2017 < 0.05 Spring 0.11 Table 6-10. Enriched tritium data in the Silala basin. 6.6.2.3 Carbon-14 data C-14 (see Herrera and Aravena (2017) for more detail) values range from 9 pMC (percent Modern) to 78 pMC, where the lowest values were found in groundwaters (9-14 pMC), the intermediate values were found in river water and springs in the upper course of the Silala River and Quebrada Negra (SP-SI-15-17 and SP-SI-10-17) (26-45 pMC), and highest values are found in springs in the northern lower course of the Silala River (SP-SI05-16 and SP-SI-8-17 with values between 76-78 pMC) (Figure 6-29). The low C-14 values observed in the groundwater, indicating relatively longer storage time, confirms a more regional nature of the flow system for the ignimbrite aquifer (HU3), probably recharged in the high Andes, perhaps several kilometers away from the study zone. The river water and spring waters from the upper course of the Silala River and Quebrada Negra, which were also recharged in the high Andes, indicate shorter storage time than for the deep groundwaters (intermediate C-14 pMC values). Finally, the springs in the northern lower course of the Silala River, which are interpreted as recharged locally, show the shortest storage time (highest C-14 pMC values). 266
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ID sample Water Type
14C
pMC ± 1σ
R-SI2-16 River 26.66 0.13
SP-SI05-16 Spring 76.86 0.35
PW-BO-B-16 Groundwater 9.93 0.08
PW-UQN-B-16 Groundwater 14.54 0.09
R-SI-3-17 River 45.97 0.27
SP-SI-8-17 Spring 78.39 0.24
SP-SI-15-17 Spring 32.41 0.15
SP-SI-10-17 Spring 30.06 0.15
Table 6-11. C-14 data for river, springs and groundwater in the Silala River basin.
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169 Figure 6-29. Distribution of 14C sampling points in the Silala River basin. From Herrera and Aravena (2017). 6.7 Recharge Most of the precipitation in the Silala basin falls in the summer period between January and the end of March, with very little falling in the other nine months (Muñoz et al., 2017). Infiltration capacities and permeabilities in the alluvial deposits (HU2), fluvial deposits (HU1), ignimbrites (HU3), and andesitic and dacitic volcanic rocks (HU5) are sufficient that little precipitation would run off, although in very severe storm events this has been observed. After the surface soils/sediments have become wetted most of the rainfall or snowmelt would be likely to infiltrate, thus minimising evaporation. Geochemical and environmental isotope data show that the recharge to the ignimbrite aquifer(s) probably originates in the high Andes. The groundwater in the deep 268
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ignimbrite aquifer(s) is confined and under a pressure head higher than atmospheric so
recharge must be occurring some distance (perhaps several kilometers) away from the
drilled boreholes and at a higher elevation. Although these areas are unknown, they may
be provided by the large outcrop area of Cabana Ignimbrite in Bolivia (to the north east
of the Orientales wetland) or could also be provided from the lavas flanking the Volcán
Apagado in Chile and Bolivia or yet other areas.
On the sides of the Cerro Inacaliri it seems likely that a discontinuous but extensive
shallow perched aquifer receives recharge to shallow water tables within the alluvial
deposits (HU2) which overlie the ignimbrites in much of the basin. This water appears
to supply the springs that flow into the Silala River from the walls of the ravine.
As shown by the geochemical and environmental isotope data, the recharge for the
shallow alluvial aquifer that feed the springs on the northern side of the lower course of
the Silala River is of local origin.
The fluvial sediments (HU1) in the ravine are often very permeable and rainfall would
tend to infiltrate rapidly, but the areal extent of these deposits is very small so the
impact of recharge through these deposits is likely to be very small.
The flows in the Silala River respond to precipitation very rapidly but the recession to
baseflow conditions is also very rapid (Muñoz et al., 2017) indicating some rapid runoff
but that the majority of the river flow is maintained from groundwater storage. The
contribution from the artesian borehole SPW-DQN is of warmer waters that arise from
some depth in the ignimbrites. This groundwater, because of its high temperature, seems
likely to come from deeper still or/and could be associated with rocks still retaining heat
from previous volcanism, perhaps from the Volcán Apagado.
Recharge to the headwater springs that supply the Cajones and Orientales wetlands is
uncertain, but it seems likely that the precipitation of the surrounding hills formed by
the Cerro Inacaliri and Volcán Apagado and the most recent andesitic lava flow
products (HU5) have a significant role to play. They cover a large area (Figure 4-2) and
their surfaces slope toward the Orientales springs.
7 UNDERSTANDING OF THE HYDROGEOLOGY OF THE SILALA BASIN
The Silala River basin is a transboundary basin, with a drainage area of some 95.5 km2,
with 72% in Bolivian territory and 28% in the Chilean territory (Alcayaga, 2017).
The geology of the basin is dominated by volcanic rocks (mainly volcanic sequences
and ignimbrite) (Figure 7-1 and Figure 7-2), with ages ranging from Late Miocene (5.8
Ma) to Lower Pleistocene (40ky BP). These rocks are covered by more recent
sediments: fluvial, glacial, alluvial and pyroclastic fall deposits. The Silala River is
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171 incised into ignimbrite and has deposited fluvial sands and gravels on top of the ignimbrite. The ravine is between 10 and 100 m wide, with a mode of 20 m. Within the river ravine there are 4 fluvial terraces eroded into ignimbrite (T1, T2, T3 and T4) (Figure 7-2), from ~2 m to ~20 m above the current river thalweg, indicating past river activity. The current configuration of the river was probably established after T2 was formed, well before about 8,400 years BP. The hydrogeology of the Silala River basin, in the study area, is characterized by the presence of 6 hydrogeological units (HU): HU1 (Fluvial deposits), HU2 (Alluvial deposits), HU3 (Ignimbrite), HU4 (Pyroclastic fall deposits), HU5 (Andesitic and dacitic volcanic rocks) and HU6 (Weakly permeable rock). HU1 comprises moderate to high horizontal permeability Holocene fluvial deposits that appear to be unsaturated over most of their distribution, except for a restricted zone underneath the river, where they receive a water influx from the river directly above. Vertical heterogeneity of the sediments is probably great (see Latorre and Frugone, 2017) and may lead to the river being perched in some places above the lower fluvial sediments and also to perched water levels within the sediments. Fluvial deposits of HU1 have no connection with the ignimbrite HU which they overlie. HU2 corresponds to moderate to high horizontal permeability alluvial deposits of different ages (Upper Pleistocene to Holocene), composed of gravel, sand and silt, with a good distribution across the study area, mainly exposed in a planar surface to the north and south of the Silala River ravine. HU2 has an unsaturated zone throughout its occurrence, but is interpreted as supporting an extensive perched aquifer which supplies water to the many springs along the Silala ravine and its tributaries. Some parts may be unsaturated and/or ephemeral. HU3 is composed of two separate geological ignimbrite flow units: the Cabana Ignimbrite (ca. 4.12 Ma) and the Silala Ignimbrite (ca. 2.6-1.48 Ma). The rock quality of HU3 along the Silala ravine is very heterogeneous, with zones of fractures/faults and zones that are strongly weathered, where the rock is very friable and permeable. Groundwater levels obtained from wells and pumping tests indicate that HU3 contains groundwaters that are confined. Groundwater appears to flow through ignimbrite rock HU3 from NE to SW, a similar direction to the flow of the Silala River, and probably the groundwater in the fluvial deposits HU1. Pumping tests and drilling results have shown the transmissivity and storage characteristics of these deposits to vary considerably both laterally and vertically, indicating that these deposits may not act as one continuous aquifer but respond as several poorly connected aquifer(s). Borehole yields are highly variable and may be depth dependent in some areas. 270
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HU4 comprises thin Pleistocene pyroclastic fall deposits (ca. 11.7 ky BP) of moderate
to low permeability found in a restricted area.
HU5 comprises possibly moderate to highly permeable lavas of the Lower Pleistocene
and other andesitic and dacitic volcanic rocks of the Lower Pleistocene (ca. 1.5 Ma).
These rocks are products of extrusion from the Cerro Inacaliri and Volcán Apagado,
with outcrops in the highest parts of the Silala basin, where the Cerro Inacaliri and
Volcán Apagado are developed, and also in large lower areas, near the headwaters of
the Silala River. HU5 is likely to have significant permeability and storage, as these are
sub-aerial lava flows, which are likely to be highly porous and weathered.
HU6 comprise all the other rocks in the study area which are only weakly permeable.
They mainly include mainly Miocene-Pliocene Volcanic Sequences (ca. 5.8-2.6 Ma)
and minor glacial deposits (ca. 40-12 ky BP). Miocene-Pliocene Volcanic Sequences
are very heterogeneous with permeability restricted to zones with fractures, weathering
and degassing zones (bubbles). Weathering takes place mainly in the uppermost 15 cm
from surface. The Glacial deposits are lateral or terminal moraines that are
nonconsolidated, poorly sorted, clay rich sediments, interpreted to have low
permeability.
Geochemistry data indicate that the groundwater in the deep ignimbrite aquifer (HU3) is
not related to the river water or the spring water. The groundwater is low conductivity
and Calcium (Ca)-Bicarbonate type. On the other hand, the river and spring water has
even lower conductivity and is Sodium (Na)-Bicarbonate type water with relative high
content of Calcium.
Environmental isotopes show that the recharge for the groundwater in the deep
ignimbrite aquifer (HU3), river water, and springs in the upper course of the Silala
River, Quebrada Negra and southern lower course of the Silala River is of a more
regional nature, probably originating in the high Andes. On the other hand, recharge for
the springs in the northern lower course of the Silala River is of a local nature. Storage
time appears to be highest (oldest water) in the groundwater (HU3), intermediate in the
river water, and springs in the upper course of the Silala River, the Quebrada Negra and
southern lower course of the Silala, and lowest (youngest water) in springs in the
northern lower course of the Silala River. All the waters analysed in the Silala River
basin had a very low tritium content, indicating they were probably recharged before the
1960s.
The recharge of the Silala River basin originates as precipitation in highlands, which
occurs mostly during summer time and infiltrates into the surface rocks, soils and
deposits (HU1, HU2, HU3 and HU5), with probably little runoff and evaporation. The
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173 water that infiltrates flows underground from high zones to lower zones, passing through the various hydrogeological units. Water that infiltrates into the alluvial sediments (HU2) flows downgradient and emerges as springs in the rock walls of the ravine. In some cases this groundwater may travel down through alluvial/colluvial fan deposits attached to the ravine walls and through fluvial deposits (HU1), and finally reach the river in springs close to or in the river bed. The fluvial sediments (HU1) exposed in the ravine have a limited outcrop area but are often very permeable so rainfall would tend to infiltrate rapidly. Since the areal extent of these deposits is very small, the impact of recharge is likely to be very small as well. The recharge areas for the deep regional ignimbrite aquifer(s) (HU3) are unknown but could include the large outcrop of Cabana Ignimbrite in Bolivia (northeast of the Orientales wetland), and might also include be the lavas on the sides of the Volcán Apagado in Chile. Much of the precipitation over the Cerro Inacaliri and Volcán Apagado probably infiltrates in the most recent andesitic lava flow products (HU5 Andesitic and dacitic volcanic rocks), feeding the headwater springs that supply the Cajones and Orientales wetlands. 272
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Figure 7-1. Longitudinal schematic diagram along the course of the Silala River from its headwaters in Bolivia (NE to the right) to the
CODELCO Intake in Chile (SW to the left). Horizontal line in the upper left part of the diagram shows the different study locations: border
(BO), upstream Quebrada Negra (UQN), downstream Quebrada Negra (DQN) and Inacaliri Police Station (PS). Diagram is a summary of
the understanding of the hydrogeology of the Silala River basin. Discharge values from Suárez et al. (2017) and Muñoz et al. (2017).
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175 Figure 7-2. Transverse schematic diagram along the course of the Silala River. Approximate location of the diagram is shown by a red bold vertical line labelled “cross section” in previous figure. Diagram is a summary of the understanding of the hydrogeology of the Silala River basin. 274
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8 REFERENCES
Alcayaga, H., 2017. Characterization of the Drainage Patterns and River Network of
the Silala River and Preliminary Assessment of Vegetation Dynamics Using Remote
Sensing. (Vol. 4, Annex I).
Aravena, R., Suzuki, O., Peña, H., Pollastri, A., Fuenzalida, H.; Grilli, A., 1999.
Isotopic composition and origin of the precipitation in northern Chile. Applied
Geochemistry, 14 (4), 411-422.
Beale, G. and Read, J., 2013. Guidelines for Evaluating Water in Pit Slope Stability.
CSIRO Publishing.
Bertin, D. and Amigo, A., 2015. Peligros del volcán San Pedro, Región de Antofagasta.
Carta Geológica de Chile, Serie Geología Ambiental, No 25, p., 1 mapa escala
1:50.000, Santiago.
Clark, I. and Fritz, P., 1997. Environmental Isotopes in Hydrogeology. Lewis
Publishers.
Driscoll, F., 1986. Groundwater and Wells, 2nd ed. Johnson Screens.
Fetter, C.W., 1980. Applied Hydrogeology, 4th ed. C.E. Merrill Pub. Co.
Fritz, P. Suzuki, O. Silva, C. and Salati, E., 1981. Isotope hydrology of groundwaters in
the Pampa del Tamarugal, Chile. Journal of Hydrology, 53, 161-184.
Gayo, E. M., Latorre, C.; Jordan, T.E., Nester, P.L., Estay, S.A., Ojeda, K.F., Santoro,
Calogero M., 2012. Late Quaternary hydrological and ecological changes in the hyperarid
core of the northern Atacama Desert (~ 21°S). Earth-Science Reviews, 113(3–4),
pp. 120-140.
Hauser, A., 2004. Marco morfológico, geológico, tectónico, hidrogeológico e
hidroquímico: morfogénesis, evolución y modalidades de aprovechamiento del sistema
hidrográfico compartido chileno-boliviano del Río Silala [Morphological, Geological,
Tectonic, Hydrogeological and Hydrochemical Context: Morphogenesis, Evolution and
Modalities of Use of the shared Chilean-Bolivian Hydrographic System],
SERNAGEOMIN (unpublished). (Appendix A).
Herrera, C., Pueyo, J., Sáez, A. and Valero-Garcés, B., 2006. Relación de Aguas
Superficiales y Subterráneas en el Área del Lago Chungará y Lagunas de Cotacotani,
Norte de Chile: un Estudio Isotópico, Revista Geológica de Chile, Vol. 33, N° 2, 299-
325.
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177 Herrera, Ch. and Aravena, R., 2017.Chemical and Isotopic Characterization of the Surface Water and Groundwater of the Silala River Transboundary Basin, Second Region, Chile.(Vol. 4, Annex III).Latorre, C. and Frugone, M., 2017.Holocene Sedimentary History of the Río Silala (Antofagasta Region, Chile).(Vol. 5, Annex IV).Magaritz, M.; Aravena, R.; Peña, H.; Suzuki, O. and Grilli, A., 1989. Water chemistry and isotope study of streams and springs in northern Chile.Journal of Hydrology, 108,323-341.McRostie V., 2017.Archaeological First Baseline for the Silala River Chile.(Vol. 5,Annex VI).Muñoz, J.F.; Suárez, F.; Fernández, B.; Maass, T., 2017. Hydrologyofthe Silala River Basin.(Vol.5, Annex VII).Sáez,Alberto; Godfrey, Linda V.; Herrera,Christian; Chong,Guillermo; Pueyo, Juan J., 2016.Timing of wet episodes in Atacama Desert over the Last 15ka. The Groundwater Discharge Deposits (GWD) from Domeyko Range at 25°S. Quaternary Science Reviews,145, 82-93.SERNAGEOMIN,2017. Geology of the Silala River Basin.(Vol. 5, Annex VIII).SoilMoisture Equipment Corp. 2012, Guelph Permeameter 2800 Operating Instructions. Suárez, F.; Sandoval, V.; Sarabia, A., 2017.River-Aquifer Interactions Using Heat as a Tracer in the Transboundary Basin of the Silala River.(Vol. 5, Annex X).Todd, D.K.,1980.Groundwater Hydrology, 2nd edn.John Wiley and Sons, Inc. Uribe, J., Muñoz, J.F., Gironás, J., Oyarzún, R., Aguirre, E., and Aravena, R., 2015.Assessing groundwater recharge in an Andean closed basin using a rainfall-runoff model and isotopic characterization, Salar del Huasco basin, Chile. Hydrogeology Journal, 23,1535-1551.United States Geological Survey (USGS), 2015. National field manual for the collection of water-quality data. Techniques of water-resources investigations, book 9, Handbooks for Water-Resources Investigations. 276
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178 9ACKNOWLEDGEMENTS This report is the result of a huge effort over a long period. It involved several professionals from the Arcadis team who participated in different stages of the investigation, from data collection in the field to interpretation of results and writing of different chapters of the report. We appreciate the long hours of dedicated work in the field that was put in by our collaborators during the different campaigns. Also we would like to thank our project coordinator and health and safety professionals for organizing all the tasks and keeping us safe. The Carabineros de Chile also played an important role in safety and organization.Similarly we aregratefultothemanyprofessionals who helpedinterpretthedata and wrote chapters of the report. We also wouldliketothank the continuous feedback of ourWater Resources Manager and Hydrogeology ChiefGeologistwhoprovided many inspiring ideasanddiscussions.Finally we acknowledge the revisions, comments and constructive discussion with the international experts in hydrogeology and hydrology as well as the discussion with other members of the science team (outside Arcadis) which was very insightful. A special mention must be made to the Difrol team, who organized data, reports, fieldtrips, and scientific discussions.
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278
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APPENDIX A
SUMMARY OF REPORTS
1. Summary of literature
This chapter provides a summary of the material that is pertinent tor this Study.
Gayo et al., 2012. Late Quaternary hydrological and ecological changes in the
hyper-arid core of northern Atacama Desert (~21ºS). Earth-Science Reviews, 113(3-
4), pp. 120-140.
This work provides information on wet episodes during the late Pleistocene to
Holocene, made evident in the basin of Pampa del Tamarugal (21ºS, 900-1.000 metres
above sea level). Based on the analysis of fossil vegetation found in relic fluvial terrace
deposits, inside 4 dry ravines without current vegetation, 3 river and wetland expansion
stages were interpreted at the following times: (1) 17.6-14.2 ky BP, (2) 12.1-11.4 ky
BP, and (3) 1.01-0.71 ky BP. Besides the plant debris, archaeological artefacts from the
early and late Archaic Period were found, indicating human presence that was
facilitated by the existence of water in a hyper-arid Atacama Desert.
These wet periods are correlated with regional events with increased rainfall in the
Central Andes (Central Andes Pluvial Events or CAPE) (CAPE – 17.5-14.2 ky BP to
13.8-9.7 ky BP).
The interpretation made by the authors was that these wet episodes would be related to
variability in precipitation in the high areas directly east of the study area of the Silala
River ravine, during the late Quaternary.
Hauser, A., 2004. Morphological, Geological, Tectonic, Hydrogeological and
Hydrochemical Context: Morphogenesis, Evolution and Modalities of Use of the
shared Chilean-Bolivian Hydrographic System. National Geology and Mining
Service (SERNAGEOMIN). Unpublished. Original in Spanish and English
translation are enclosed in this Appendix.
This report was aimed at gathering, broadening, and supplementing the existing
technical data and reports available in the literature on the Silala River basin. It was
mainly based on previous studies conducted by the same author. In order to achieve this,
two trips were made to the Chilean segment of the Silala River and one trip was made to
the Bolivian part of the river system during October 2000, accompanied by a delegation
of Bolivian technical experts and professionals. According to the author, the
measurements and observations made during the trip helped to irrefutably confirm the
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279
2 nature of the Silala as a natural river, whose headwaters and discharge bed have been carved out in ignimbrite sequences. The Silala River headwaters correspond to two typical highland wetlands (Cajones and Orientales). These wetlands are fed by springs emerging from the sides of the lobe of a lava flow sourced in the Cerro Inacaliri o del Cajón (“Cerro Inacaliri”) volcano, deposited on top of ignimbrite rock. The natural slope towards the west of the area ensures the river discharge towards Chilean territory, which is typical of an exorheic basin of the Andean Highlands. Hauser asserts that the presence of springs at the headwaters is evidence of conditions controlled by a hydraulic head, therefore the channelization works carried out in the early twentieth century do not have any bearing on forcing this flow towards Chilean territory. He also stated that the geological and morphological characteristics of the area established that the waters of the Silala River flowed naturally towards Chilean territory before the construction of the intake works. In chemical terms, the waters under analysis are mainly sodium bicarbonate with low content of dissolved salts which he interprets as corresponding to recharge from meteoric waters associated with the present local rainfall pattern. Lastly, he asserts that the Silala River possesses the unmistakable character of a binational river. Sáez et al., 2016. Timing of wet episodes in Atacama Desert over the last 15 ka. The Groundwater Discharge Deposits (GWD) from Domeyko Range at 25°S. Quaternary Science Reviews, 145, pp. 82-93. This paper includes a palaeo-climatic reconstruction for the Atacama Region, showing the occurrence of periods with more humidity, controlled mainly by the distance to the sources and altitude. In the northern sector of Atacama it is possible to identify at least 4 wet periods associated with monsoon precipitation that have been related to the Tauca and Coipasa phases during the last Ice Age. 2. Analysis of strength and weakness of each work Next is Table 1–1 that presents the records’ analysis. It shows the study area of each reference (location), followed by information of interest for the present study, and concluding with the analysis of strengths and weaknesses. 280
Annex II Appendix A
3
Author Year Title Location Information of
Interest Strengths Weaknesses
Gayo et al. 2012 Late Quaternary
hydrological and
ecological changes
in the hyper-arid
core of northern
Atacama Desert
(~21ºS)
Pampa del
Tamarugal
(21ºS, 900-
1,000 m.a.s.l.)
1. Interpretation of 3
expansion stages of
wetlands and
permanent rivers:
(1) 17.6-14.2 ky,
(2) 12.1-11.4 ky,
and (3) 1.01-0.71
ky. The last stage
could be correlated
with terrace T2 in
Silala, 600 years
BP.
1. Interpretation based
on evidence of
organic matter,
datings, as well as
archaeological
material.
-
Hauser 2004 Morphological,
Geological,
Tectonic,
Hydrogeological
and
Hydrochemical
Context:
Morphogenesis,
Evolution and
Modalities of Use
of the shared
Chilean-Bolivian
Hydrographic
System
Silala basin,
Second Region
of Antofagasta
1. Conceptual
considerations of
arguments from the
Republic of
Bolivia.
2. Geological and
morphotectonic
local context of the
studied area.
3. Synthesis of
information from
trial pits and
boreholes executed
on site.
4. Conceptual
framework of the
1. Clearly presents the
technical arguments
of Bolivia to justify
their position.
2. Clearly presents the
sectors where the
waters that give rise
to the Silala River
well up, and where
extractions are
being made.
3. Synthesis of the
technical
information of
boreholes and trial
pits.
1. Some diagrams
and figures
present little
detail.
2. The geology is
lacking in
detail in the
sector.
3. Does not
present the
hydrochemical
data with their
respective
values.
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281
4 Author Year Title Location Information of Interest Strengths Weaknesses hydrochemistry in the Silala River, wetlands, and drainage system. 4. Rebuts with clarity the arguments presented by Bolivia. Sáez et al. 2016 Timing of wet episodes in Atacama Desert over the last 15 ky. Groundwater Discharge Deposits (GWD) from Domeyko Mountain Range at 25°S Domeyko Mountain Range 1. Stratigraphic correlations and associations to monsoon events. 1. Provides diagrams and periods of wet activity. 1. For the time and space scale, the paper is a guide at macroscopic level, but not at the detail of the present study. Table 1–1. Summary of collected records, highlighting strengths and weaknesses. 282
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5
HAUSER, A., 2004. Morphological, Geological, Tectonic, Hydrogeological and
Hydrochemical Context: Morphogenesis, Evolution and Modalities of Use of the Shared
Chilean-Bolivian Hydrographic System. National Geology and Mining Service
(SERNAGEOMIN). Unpublished. Original in Spanish and English translation.
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284
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(Logo: Government of Chile National Geology and Mining Service)
NATIONAL GEOLOGY AND MINING SERVICE
NATIONAL SUB-DIRECTORATE OF GEOLOGY
MORPHOLOGICAL, GEOLOGICAL, TECTONIC,
HYDROGEOLOGICAL AND HYDRO-CHEMICAL CONTEXT:
MORPHOGENESIS, EVOLUTION AND MODALITIES OF
THE EXPLOITATION OF THE SHARED CHILEAN-BOLIVIAN SILALA RIVER
SYSTEM
(Consolidated Report)
Arturo Hauser Y.
Geologist
Santiago, October 2004
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CONSOLIDATED REPORT
MORPHOLOGICAL, GEOLOGICAL, TECTONIC,
HYDROGEOLOGICAL AND HYDRO-CHEMICAL CONTEXT:
MORPHOGENESIS, EVOLUTION AND MODALITIES OF
THE EXPLOITATION OF THE SHARED CHILEAN-BOLIVIAN SILALA RIVER SYSTEM
Arturo Hauser Y.
National Geological and Mining Service
INTRODUCTION
For the past 4 years, the Chilean-Bolivian controversy regarding the binational or shared waters of the hydrographic basin of the Silala River, located in the Second Region, has generated a significant demand of information referring – among others – to the morphological, geological, tectonic, and hydrogeological aspects, and to the modalities of the current exploitation of the surface water resource.
The elaboration and content of this final Report, prepared by the National Sub-Directorate of Geology, of the National Geology and Mining Service (SERNAGEOMIN, by its acronym in Spanish), is aimed at satisfying these requirements. As a result thereof, this consolidated document attempts to gather, expand, complement and update the technical records contained in three previous reports that the Directorate of Borders and Boundaries of the State (DIFROL) of the Ministry of Foreign Affairs requested from SERNAGEOMIN, which were carried out between 1999 and 2000.
Therefore, the knowledge base and records provided in the present Document is supported by three unpublished previous reports of the author (Hauser, 1999a, 1999b and 2000), by two visits to the Chilean section of the Silala River, and by a visit carried out during October 2000 to the Bolivian section, corresponding to the headwaters of the Silala River system, in the company of a delegation made up of professionals and technicians from various government institutions of the Republic of Bolivia.
The provided information is further supported by a detailed bibliographic revision of articles published in technical journals and in numerous textbooks, mostly corresponding to authors that, at an international level, possess an accepted scientific backing and value: Bloom (1991); De Pedraza (1996); Branson & Tarr (1964); Bruggen (1950); American Association of Petroleum Geologists (1982); Geoscience Canada (1983); Clapperton, C. (1993); Society of Economic Paleontologists and Mineralogists (1987).
LOCATION OF THE STUDY AREA
According to its unique shared or binational nature, the hydrographic basin of the Silala River (hereinafter “the SHRS”) includes terrains located along the boundary of the Republics of Chile and Bolivia. The headwaters of said river are located in the latter, involving a sector of highlands located on the Quetena Canton, Province of Sud Lípez, in the Department of Potosí, Republic of Bolivia. The end section of the Silala River, before reaching the Inacaliri River, is located in the district of Ollagüe, Province of El Loa, Second Region of Chile, 125 km Northeast of the city of Calama
(Fig. 1).
The waters of the Silala River enter national territory through a deep canyon or ravine, carved out by a lengthy fluvial to fluvio-alluvial activity. In this sector, the boundary is established according to a 7.0 km-long rectilinear trace, in a North 45° West direction, that connects the highest points of the Inacaliri or Cerro Inacaliri or del Cajón (5,625 meters above sea level, m.a.s.l.) with the Cerro Silala, Boundary marker LXXIV (4,850 m.a.s.l.).
The interest zone is accessed from the city of Calama, by a road that is approximately
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145.0 km long. The first 75.0 km up to the sector of the Conchi reservoir are paved, whereas the remaining 70.0 km only record a stabilized gravel course.
CONCEPTUAL CONSIDERATIONS ON WHICH THE ARGUMENTS OF THE REPUBLIC OF BOLIVIA ARE BASED
At a meeting held with professionals from various Bolivian government institutions, the bases that support their current position regarding the Silala River controversy were established. Said meeting took place on August 23, 2000, in the city of Santa Cruz de la Sierra, Bolivia.
Generally speaking and only referring to the aspects of interest for the purposes of this Document, the stated arguments involve the following statements:
-
The existence of the Silala River is not recorded, but rather that of “the Silala springs”.
Fig. 1- Study area
Legend:
International boundary
Regional boundary
Paved road
Unpaved road
Railway line
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290
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-
A spring may only give rise to a river, if it is concentrated and not disperse, as is the case with the Silala, where the existence of at least 70 “ojos de agua” (water holes that form ponds) would be verified, each one having reduced volumes of flow.
-
The water resource generated in the area would not fulfill the necessary conditions to be categorized or regarded as shared or binational.
-
The ravine along whose bottom the sum of the waters run, would have its origin in erosive activity due to wind.
-
The construction of some civil works, namely canalizations, drains and stonework lining in some riverbed segments, would have been decisive for enabling the runoff of the waters to Chilean territory. This argument, in its turn, is based on the following considerations:
a)
Low local rainfall (5 mm/year).
b)
Reduced surface of the contributing hydrographic basin.
c)
Prevalence of terrain with impermeable rocks.
d)
The large dispersion of the “ojos de agua”, which feed the springs or wetlands of Cajón [Cajones] and Orientales and would hinder the development or formation of a river.
e)
Gentle local slope.
f)
Forced reduction of the original surface of both wetlands by anthropogenic intervention; it is assumed that due to the extractions of water from both springs or wetlands, these would have suffered a 30% reduction with respect to their original surface.
-
The civil works executed at the beginning of the 20th Century by The Antofagasta (Chili) and Bolivia Railway Company Limited (FCAB, in Spanish) and designed to collect the waters of the SHRS, are completely lined with stonework.
-
In the area, the two springs or wetlands take part in a local modeling which is typical of a closed or endorheic basin.
-
In particular, the depression area that contains the current Cajón spring or wetland would have a predominantly glacial origin.
-
The current structure that transports the waters of the “Silala springs” (the ravine of the Silala River) would correspond to eolic genetic mechanisms.
-
Trial pit prospecting carried out around the riverbed and springs or wetlands of the Silala River, in the Bolivian sector, would have allowed recognizing the presence of granular deposits linked to glacial processes, in no case to fluvial processes.
For the Bolivian party, the preceding formulations or statements have allowed supporting the following hypothesis and demands:
a)
The scientific and technical studies conducted in the area make it possible to reject or question the existence of the Silala River. According to this, some Bolivian authors apply the concept of “the Silala myth” (Bazoberry, 2003).
b)
What exists in the sector corresponds to the “Silala spring”.
c)
The current discharge bed of the “Silala spring” would not correspond to a natural structure resulting from fluvial to fluvio-alluvial activity during the geological past, but rather from human intervention, carried out towards the beginning of the 20th Century (drains, canalizations, linings), sufficient and necessary to force the waters to run towards Chilean territory.
d)
The mentioned anthropogenic interventions would have transformed an originally endorheic (closed) hydrographic basin into an exorheic (open) basin.
e)
The discharge of the “Silala spring” waters towards Chilean territory would involve an “artificial hydraulic system”.
f)
It is considered that in the “Silala spring” area, the low level of rainfall (rated at only 5.0 mm/year) would have been absolutely insufficient to generate a concentrated surface flow with energy compatible with the possibility of giving shape to a natural discharge or spillage bed of the waters towards Chilean territory.
g)
Acknowledging of the existence of the “Silala spring” together with disregarding the presence of the Silala River, plus the affirmation that the water discharges towards Chilean territory
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in response to anthropogenic interventions, determine that the surface water resource that is present in the sector does not fulfill the characteristics of being shared or binational.
h)
The preceding considerations are the basis of the Bolivian government´s position to establish that the current exploitation of the water resource in Chilean territory – as it does not adjust to inter-nation norms that govern these proceedings - may only be carried out via prior economic settlements; this, without excluding possible charges for the already exploited resources.
LOCAL MORPHOLOGICAL, GEOLOGICAL AND TECTONIC CONTEXT
From a morphological viewpoint, as a result of its particular climatic, geological and structural conditions, the study area accounts for a terrain that is markedly contrasting, both in the meridian and longitudinal aspects. The volcanic modeling adds striking connotations to the landscape due to the diversity of the shapes and dimensions of their expressions, which range from voluminous cones, extensive lava and pyroclastic covers to lesser plains and/or depressions.
The area involved in the SHRS basin includes undoubtedly highland terrains, genetically and mainly associated with a relatively young volcanic chain, which in the sector takes part in vast segments of the boundary watershed with the Republic of Bolivia.
It is therefore a high Andean environment, whose “lowlands” have mean heights that range from 4,300 to 4,500 m.a.s.l., which culminate in numerous volcanoes having a maximum height between 5,500 to 6,000 m.a.s.l. The greatest elevations correspond to a series of stratovolcano-type structures: Inacaliri o del Cajón, Silala, Apagado, Silaguala and Cerro Negro or Pabelloncito, the latter being in Bolivian territory. This type of volcano is characterized by shaping edifications endowed with conic silhouettes, a circular base, rounded tops, associated to formative mechanisms that involve successive superimposed lava flows or melts. There is a prevalence of andesitic, basaltic to basaltic andesite materials that are dark, unaltered, resistant, having a fresh appearance (PlQv and Qvm in Fig. 2).
In sectors, the eruptive activity is expressed in the development of domes, lava-domes or lava flows, which because of the high viscosity of the emitted materials acquire the shape of vast flat surfaces, very uniform, endowed with rather steep slopes or hillsides, while the ignimbritic flows are part of flat surfaces made up of successive alternating layers of breccia, tuffaceous breccia and tuff with predominantly pink colors, Cabana Ignimbrite (Qca in Fig. 2 and Photo 1).
The “youth” of these structures determines the development - in some sectors of their abrupt hillsides – of a series of lineal incisions, small ravines, of diverse length and depth, carved out by the water-type erosive action, linked to the effects of short-lived runoff, as well as to direct rainfalls, snow melts or mixed processes. On site, these structures configure singular radial drain patterns that begin around the top of the respective hills or volcanoes.
Mortimer (1980) considers that most of the landscape and the drainage system of our highland area may have developed and been established as of the end of the Tertiary period.
Available radiometric values indicate that most of the volcanic activity that produced the current “highland landscape” around the interest area, would have started in the Upper Miocene, 5.5 to 6.3 million years BP (before present) and had interrupted development until the present (Marinovic & Lahsen, 1984).
In addition, the “lowlands” around the described volcanic centers involve relatively flat to semi-undulating terrains, shaped as potent accumulations of volcanic (lava flows) and volcanoclastic (ignimbrites) deposits. These are genetically and primarily associated to explosive eruptive activity from the so-called Pastos Grandes calderas, located in Bolivian territory, 55.0 km Northeast from the point where the Silala River enters Chilean territory, and/or Pacana, located East of Salar (salt flat) de Atacama and regarded as the largest South American caldera
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293
294
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Fig. 2- Main eruptive centers around the Silala River hydrographic basin.
Photo 1- General view of Volcán Inacaliri o Cajón. In the foreground, sub-horizontal ignimbrite sequence. Cabana.
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296
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(60.0 x 35.0 km) (Clapperton, 1993, p. 128). The first involves a structure of about 55.0 km in diameter, with a resurgent point represented by Cerro Pastos Grandes that is 5,800 m.a.s.l. (González-Ferrán, 1994) (Fig. 2). The most recent eruptive activity of this caldera is represented by the lava-dome of Cerro Chascón, whose age is estimated to be Holocene (at least 10,000 to 11,000 years BP) (González-Ferrán, op cit). The lavas mainly correspond to the andesitic and dacitic types, while the ignimbrites correspond to crystal tuffs, moderately welded, in pink hues.
The aforementioned rocky materials are observed discontinuously coated with a variety of sedimentary deposits genetically linked to erosion, transport and deposition from glacial, fluvial, glacifluvial, alluvial, eolic activity. These appear in the form of banks or strata, which are concordant, integrated by hetero-compositional clasts, sub-angular to sub-rounded, unaltered, resistant, and encased in a fine matrix ranging from gravel to sand. As a whole, they denote moderate porosity and permeability; low to moderate compactness.
From a tectonic viewpoint, the high Andean area of interest for the purposes of this Document corresponds to a territory with a predominance of normal fractures or faults, of regional range, having a dominant North-South direction; the lesser or secondary faults have Northeast and Northwest directions that intercept the first. From a genetic viewpoint, it is assumed that most of the tectonic activity that generated the previously described structures would have started from a comprehensive phase that began in the Middle Miocene (10.0 to 11.0 million years BP), culminating in an extensive episode during the Plio-Quaternary Period (2.0 to 2.4 million years BP) (Marinovic & Lahsen, 1984).
The described tectonic system favored the subsequent eruptive activity that took place in the area: formation of volcanoes, domes, and lava-domes. This singularity is expressed in the fact that the main issuing centers align according to the dominant centerline of the larger structures. Actually, they would have conditioned or favored the ascent of the various magmatic flows.
Fig. 3 provides the geological-structural context of the study area according to Ramírez & Huete (1981) and Marinovic & Lahsen (1984).
Fig. 3- Geology around intakes of surface waters of the Silala River.
LEGEND
Qfa Fluvial to fluvio-alluvial deposits
Qc Colluvial deposits
Qvm Eroded andesitic stratovolcanoes (Upper Miocene – Pliocene)
PlQv Andesitic volcanoes (Pliocene – Holocene)
Qca Ignimbrite Cabana
Qv Andesitic lava flows (Pleistocene – Holocene)
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PROSPECTING OF THE TERRAIN
Based on the need to have reliable information about the subsurface terrain and considering that around the present riverbeds of interest, the development of plant coverage makes it difficult to recognize the type, the particle size characteristics and continuity (in the lateral sense) and the depth of the sedimentary filling; the decision was made to project and excavate an exploratory trial pit. The supplied background information was complemented with the analysis of the information available that was generated during the drilling of two deep wells for groundwater prospecting in sections of the Silala riverbed.
Trial Pits
These were executed around Intake C-1 (Fig. 4). Their stratigraphic record gave the following result:
-
H-1: 0.0 to 0.80 m. Riprap, gravel and sands, dark gray in color; 30% clasts, stones 30 to 35 cm in diameter; 30% clasts 15 to 25 cm in diameter; and 40% gravel to sandy gravel, with few interstitial fines. 90% of clasts correspond to andesites (aphantic and porphiric), dark, unaltered, resistant, sub-angular to sub-rounded. 10% of ignimbritic clasts are tabular, with pink hues. Small percentage
(< 10%) of non cohesive fines. Between 0.20 to 0.30 m, there is a recorded increase in blackish argillaceous material, quite plastic with sufficient moisture, that includes abundant organic matter (plant remains from palaeo-soil). GP type soil, in the Unified Soil Classification System (poorly graded gravel with few fines). Photo 2. The superficial 0.30 to 0.35 m could correspond to material similar to artificial filling.
-
H-2: 0.80 to 1.70 m. Riprap, gravels and sands, light gray in color; 50% of clasts, stones having a mean diameter of 25 to 30 cm; 30% of clasts having a diameter of 8.0 to 10.0 cm; and 20% of gravel to sandy gravel, with few cohesive fines (silt-clay); 80% of clasts are andesites (aphantic and porphiric), blackish, unaltered, resistant, and sub-rounded. 20% of clasts are ignimbritic, mostly tabular and presenting pinkish hues; very few plant remains. GP type soil in the Unified Soil Classification (poorly graded gravel with few fines), Photo 3.
-
H-3: 1.70 to 2.30 m. Riprap, gravels and sands, grayish color; 30% of clasts have a mean diameter of 20.0 m; 30% of clasts have a mean diameter of 10.0 to 15.0 m in diameter; 40% of gravels and sandy gravels have few interstitial fines (silts and clayey silts). Clasts are mostly andesitic (aphantic and porphiric), dark, unaltered, resistant, and sub-rounded. GP type soil in the Unified Soil Classification (poorly graded gravel with few fines).
Lava flows
Alluvial cone, gavels and sands
Surface water intakes of
Silala River
Wetland
Boundary marker
Silala River channeled at the
bottom of deep, narrow ravine
Silala River with little canalization
Springs
Profile
Exploration drilling
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Table 1 (annexed) provides the results of the particle size analyses for the three samples extracted from the trial pit, analyses that were carried out by the Materials Research Lab of Universidad Católica del Norte (LIEMUN in Spanish), at the Antofagasta branch.
Table 1- Particle size analysis
Sieve No.
% that passed through sieve
S A M P L E S
H-1
H-2
H-3
3 ½’
100
100
100
3’
80
8
72
2 ½’
75
81
64
2’
71
77
54
1 ½’
68
70
46
1’
62
60
36
¾’
59
54
33
3/8’
52
44
25
4
46
35
20
10
41
25
15
40
32
12
8
200
12
1
1
Photo 2- Granular materials: fluvial sands, gravels and riprap, corresponding to Horizon H-1, from a 3.2 m deep trial pit, excavated around Intake C-1. Sub-angular to sub-rounded clasts, andesitic, 90%, and ignimbritic and brecciated (10%), unaltered, resistant, having a fresh appearance. Approx. scale 10x16 cm.
Photo 3- Granular material corresponding to Horizon H-2, from the trial pit excavated around Intake C-1. Fluvial deposits with smaller proportion of fines, in comparison to overlying horizon; sub-rounded clasts, unaltered, encased in gravel and sands.
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Fig. 5 shows the respective particle size curves of the 3 samples, corresponding to each of the horizons sampled in the exploration trial pit that was made around Intake C-2.
Fig. 5- Particle size curves of sediments extracted from the trial pit made around Intake C-2.
Values recorded in Table 1. (Left: fine aggregate; right: coarse aggregate)
In the three cases, these are gravels and sands, slightly argillaceous, with abundant stones having rounded to sub-rounded edges, unaltered, resistant, having a fresh appearance. The materials described in situ (walls of the trial pit) show slight stratification; the tabular clasts, mostly ignimbritic, develop an incipient imbrication (overlapping); moderate to low compactness, increasing with depth. The group of particle size, textural and sedimentary properties is typical of a sequence having a fluvial to fluvio-alluvial origin.
Determinations of the Atterberg Limits or (Soil) Moisture Constants for all samples gave a value of NP (Non Plastic).
According to the statements made by Bolivian technicians at an official meeting in Bolivia, at least 8 trial pits had been made with a mean depth of 1.45 m. Out of these, 4 were excavated in the main riverbed of the discharge ravine of the Silala River; 3, around the springs of the Orientales wetland; and 1 around the springs of the Cajón wetland. In all cases, the sedimentary sequence would record a prevalence of granular materials (riprap and sandy gravels), very similar to those detected in the single trial pit excavated in Chilean territory.
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Exploration Drillings of Underground Waters
During 1999, under mandate of the FCAB company, the firm CAPTAGUA carried out two exploration probes intended to prospect for the presence of groundwater in the sedimentary filling of the ravine that contain the Silala riverbed; the drilling took place immediately downstream of Intake C-2 (Table 2) (Fig. 4 and Photo 4).
Table 2- Summary of some characteristics of the two probes
Probe
Depth (m)
Bedrock
(m. below intake)
Static level (m)
Flow (l/s)
S-1 /No. 3038)
62.0
9.0
Upwelling
60
S-2 (No. 3102)
70.0
58.0
Upwelling
115
Photo 4- Adduction that leads the waters from Intake C-2 of FCAB.
In the central part of the photo one can see the exploration probe S-1.
Stratigraphic Description of Probe S-1.
(From the record made by the engineer Mr. Rafael Larraín Ibañez, CAPTAGUA)
-
0.00 – 1.50 m Stones and sand
-
1.50 – 2.00 m Stones, sand, clay 20%
-
2.00 – 3.00 m Stones, sand, clay 25%
-
3.00 – 4.00 m Stones, sand, regular gravel, clay 5%
-
4.00 – 5.00 m Stones, medium to fine sand, clay 25%
-
5-00 – 7.30 m Stones, medium to fine sand, clay 30%
-
7.30 – 9.00 m Stones, medium to fine sand, clay 25%
-
9.00 – 62.00 m Bedrock. Ignimbrite.
Stratigraphic Description of Probe S-2
(From the study made by consulting geologist Mr. Carlos Parraguez Decker)
-
0.00 – 13.0 m Stratum of coarse to fine sands whose greater clastic fraction represents close to 20% of the total deposit, and the matrix, 80%. The matrix fraction is formed by fine to very fine sand and clays between 20 and 30%.
-
13.0 – 29.0 m Stratum whose greater clastic fraction grades from coarse gravel to coarse sand
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(15 to 30%), and the matrix, 70 to 85% is made up of medium to fine sands with proportions of silt and clay that can amount to about 20%.
-
29.0 – 58.0 m Level of greater particle size whose clastic fraction grades from fine riprap to coarse sand (15 to 25%), and whose matrix (75 to 85%) varies between medium coarse sand to fine sand, with proportions of silt and clay amounting to less than 10%. This stratum has the characteristics of a good aquifer.
-
58.0 – 62.0 m Gray volcanic rock, andesite – dacitic in nature, with pink cineritic levels (ignimbrite?).
By carrying out these two probes and their respective pumping tests, it was possible to determine:
a)
The sedimentary character, continuity and thickness of the fluvial to fluvio-alluvial sequence, that is part of the basal filling of the ravine which currently contains the riverbed of the Silala River, immediately downstream from Intake C-2, of FCAB in Chilean territory;
b)
The presence, type and characteristics of aquifers;
c)
Hydrogeological potential of the sequence;
d)
Physicochemical quality of the waters; and
e)
The link or interference between the aquifer and the superficial runoff waters.
The stratigraphic record made it possible to establish a singular irregularity of the bedrock in the 65.0-m segment comprised between the two probes. This situation may be explained by two alternatives: a) an intense, concentrated differential erosion due to fluvial erosive activity, and b) an intervention of tectonic mechanisms.
The presence of a surging aquifer would be controlled by the existence of an upper sedimentary sequence (<10 m), which is thin and therefore somewhat more permeable. This singularity, additionally, would determine a hydraulic disconnection between the local aquifer system and the surface runoff in segments downstream from the Silala River, with regard to the location of the Intake C-2 structure in Chilean territory (Fig. 4). This fact was made evident from the moment that, during the respective pumping tests at each of the probes, the flow rate of the Silala River did not experiment alterations.
HYDROCHEMISTRY
The three field campaigns allowed taking samples of the waters of the Silala River in various segments of its riverbed. The samples were analyzed at the Chemical Lab of SERNAGEOMIN in Santiago. The denominations and locations thereof are recorded in Table 3 and Fig. 6.
Table 3- Denominations and Locations of Surface Water Samples
Denomination of Sample Location of Sample
Sample 1
Intake C-1 of FCAB, in Chilean territory
Sample 2
Intake C-3 of CODELCO
Sample 3
Orientales tributary, immediately upstream from confluence with Cajón tributary
Sample 4
Cajón tributary, immediately upstream from confluence with Orientales tributary
According to the Piper Diagram, recorded in the attached Fig. 6, it is mainly sodium bicarbonated waters having a pH value ranging from 8.10 to 8.86, moderate to low levels of mineralization (95 to 149 mg/l of dissolved solids by evaporation). This property would answer for relatively ‘juvenile’ waters (little residence time), genetically linked to rain, meteoric or modern waters. They have an As content ranging between 0.01 to 0.17 mg/l;
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Chilean Potable Water Standard (NCh 409/1, Document 84) accepts contents of up to 0.05 mg/l of As.
Annexed hereto are the certificates of the four water samples analyzed at the Chemical Lab of SERNAGEOMIN.
Fig. 6- Piper Diagram. Types of water: A: containing sulfate and/or chloride; calcic magnesium; B: containing bicarbonate, calcic magnesium; C: containing chloride and/or sulfate, sodium; and D: containing bicarbonate, sodium.
CHARACTERISTICS OF THE SHRS: WETLANDS – DRAINAGE NETWORK AND POTENTIAL OF THE SURFACE WATER RESOURCE
At its headwaters, the SHRS involves high Andean terrains located in territories of the Republic of Bolivia, at an elevation ranging between 4,500 to 4,700 m.a.s.l.; the total surface area of its hydrographic basin has been estimated at 80.0 km2, out of which about 95% are located in Bolivian territory (Fig. 7).
The terrains that are involved in the headwaters of the Silala River basin, with a marked prevalence of frankly volcanic materials, are made up of: a) successive lava flows forming volcanic structures of the stratovolcano type, having a dacitic and andesitic composition; and b) domes, lava-domes and ignimbritic flows having a dacitic and, in a smaller proportion, rhyolitic composition.
The local rainfall patterns, concentrated during the so-called “Bolivian winter” (between the months of January to March), generates short-lived surface runoffs that have a varied dynamic. Over time, they act on rocky as well as non consolidated materials that are sensitive to water erosion.
At a regional level, this is expressed in the development of a series of lineal features, corresponding to incisions of varying depth and width: streams, brooks or creeks, which in turn come together and form progressively larger courses: ravines or canyons, at the bottom of which the waters run having different volumes of flow, canalized or semi-canalized by means of simple and/or multiple collecting structures.
The dominant North – South direction of the Andean mountain range and the steep slope of its western side, is a determining factor for the prevalence of West – East trajectories in the described structures, according to the shaping that incorporates rectilinear traces with occasional acute breaks.
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From a genetic viewpoint, it is assumed that the presence of some fractures associated to cooling mechanisms of the ignimbritic sequences may have wielded a secondary control in connection with the shaping of the local drainage network. The characteristic aridity that is typical of the highland area, determined that the fluviatile processes should have developed slowly. A large part of the highland riverbeds are contained in ravines that have deep incisions, an irrefutable sign of a dynamic of great competence.
In these environments, the interaction between certain climate processes, rainfalls, and the erosive activity associated to the concentrated runoff of the waters, may create depression zones that are favorable for the development of soggy areas with a large growth of phreatophyte plant species, called “wetlands”; an integral part of the local drainage system. Over time, these structures may become the natural sources for the current and permanent continuous supply of water around the headwaters of numerous highland hydrographic basins. In this regard, the Silala River is a good example of this mechanism.
In our country, the term wetland (“Bofedal” in Spanish) applies to Peaty meadows of infra-aquatic origin mainly made up of plants from the Cyperaceae and Juncaceae families, often having a combined or cushion growth that is found in swampy areas of the highland and puna (high Andean plateau).
The term also applies to depression terrains, poorly drained, having abundant hydrophilic vegetation, to which –by virtue of morphological considerations- surface, subsurface or underground waters associated to the local climate regime gain access.
The headwaters of the hydrographic basin of the Silala River, the Bolivian territory, tally with two wetlands: Cajón and Orientales (Photos 5 and 6).
The surface waters gain access to the wetlands by simple runoff, in response to local rainfall cycles. The underground waters do so by means of percolations associated with flows or discharges, around points where erosive activity exposes the soil / rock interface, or rocks having different hydraulic transmissibility and/or permeability. Normally, the waters well up or emerge from points where the upper limit of the saturated area reaches the surface of the local terrain.
The seasonal-character of the waters, resulting from little surface runoff, creates conditions for the layers of phreatophyte vegetation to exert an effective mechanism of discharge accumulation and regulation. This mechanism determines that, in our highland and puna areas, the wetlands constitute sources for the permanent and controlled supply of waters, which gradually as they run, create brooks, streams, creeks or rivers that are perennial. This condition is observed with greater clarity at the Orientales wetlands (Fig. 4 and Photo 7).
Fig. 7- Hydrographic basin of the Silala River
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There, the waters surface in a focalized manner around the lobular front of a vast lava flow that originated in the Eastern and Southern sides of the Inacaliri or Cajón volcano [Cerro Inacaliri o del Cajón] (Fig. 4). Morphological and geological considerations make it possible to assume that as it advanced towards the Southeast, the flow in question would have partially buried some elements of the original drainage system (segments of the main riverbed), blocking or obliterating in part the existing pattern or organization (Araya, 2003). The interface that controls the underground runoff, with final feed and discharge toward the wetland, appears to be controlled by the contact plane between the lava flow – having secondary permeability and porosity due to fracturing, and a basal ignimbrite sequence, that is impermeable (Photo 7).
Photo 5- General view of the Orientales wetland in Bolivian territory. (Far left) Note the front of lava flow that is superficially fractured and originated in the Inacaliri volcano [Cerro Inacaliri o del Cajón] crater.
Photo 6- General view of the Cajón wetland and Eastern side of the Inacaliri or Cajón volcano [Cerro Inacaliri o del Cajón]. (Upper mid sector) the presence of a probable remnant of glacial morphology can be identified, though it might also be attributed to a mass wasting process.
Photo 7- General view of the Cajón wetlands,
looking toward its headwaters, to the East.
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Around the points where the waters emerge, the rocks present patina associated with white (carbonate?) and green (Chrysocolla?) saline efflorescences (Photo 8).
The important surface fracturing that affects the lava flow capable of increasing the secondary porosity, endows it with the character of a true aquifer in a position to experience recharge, conveyance and storage of underground water. The fracture system shows two types: a) vertical fractures; and b) sub-horizontal fractures, both genetically linked to cooling mechanisms. Normally, the geometry and extension of the lava flow turns out to be determinant for controlling the storage volume. When said volume surpasses the discharge, it brings about a control regarding the flows, so that these respond with some delay or buffering of the more or less abrupt recharges that are associated with very intense rainfall cycles. This singular hydraulic behavior exerts a decisive importance or control on the generation of the base flow involved in the discharges or inflows of both wetlands (Photo 9).
On this matter, it is worth noting that testimonies from the operators of the Silala River water intake system indicate that during the cold season (“Bolivian winter”), the waters of its riverbed do not register variations in their surface runoff, confirming the capacity of supply and regulation of the wetlands. Available records allow establishing that - at least during the past 90 years - the waters would have been flowing spontaneously, with the same volume of flow, having their origin in the Cajón and Orientales wetlands.
The waters that currently spring up with plenty of energy from the fractured rocks, show signs that they are subjected to a certain hydraulic load. This hydrodynamic trait allows assuming that the upwelling acquires a natural, spontaneous character, independent of the effects exerted by possible interventions resulting from human activities linked to the execution of civil works towards the beginning of the 20th Century: drains or collection and/or conveyance ditches.
Photo 8- Water source or spring from which the waters emerge in a sector of the Orientales wetland. The rocks, corresponding to ignimbrites, present slight saline efflorescence (white and greenish).
Photo 9- Detail of the front of a lava flow, fractured and permeable. It is possible to note a slight SE incline. Overlies impermeable ignimbritic materials.
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It is worth noting that the ground reconnaissance carried out around the perimeter of the Cajón and Orientales wetlands does not allow seeing the presence of morphological remnants or plant traits linked to area modifications, possibly induced by human activity: the construction of works for extracting water from the wetlands. Around the current edges of the Orientales wetland, one cannot clearly recognize the presence of paleo-levels, corresponding to concentric “lines” developed in a time when the sector might have been occupied by a small lagoon, and “emptied” by human activity (water extraction).
In the specific case of the headwaters of the Silala River basin in Bolivian territory, the Cajón and Orientales wetlands became a constant source of water supply and regulation to the Silala River system (Fig. 4). In total, both wetlands occupy a surface area of approximately 11,000 m2, that is, 11 hectares; the larger corresponding to Orientales, with a surface area of 7.0 hectares. Even though the Cajón wetland occupies a smaller surface area than Orientales, it clearly presents a higher degree of moisture.
Once the waters have emerged, they are favored by the local slope and after entering a small riverbed, they begin their natural advance or discharge towards the West, to Chilean territory (Photos 10, 11, 12, 13, and 14). In the initial segment, the multiple, scattered transport sections show little canalization. As they advance, the riverbeds tend to occupy the bottom of a narrow ravine that gradually becomes deeper, towards the West (Photos 10, 11 and 12); after running approximately 2.7 km, the waters join the discharge bed of the Cajón wetland (Fig. 3 and Photo 15).
Photo 10- Detail of lava flow indicated in Photo 7. Superficially fractured andesitic rocks around NE side of the Orientales wetland.
Photo 11- One of the springs or water sources that give origin to the Orientales wetland. The waters discharge with plenty of energy.
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Photo 12- Discharge riverbed of the waters that originate in the Orientales wetlands, 1,300 m downstream from the point where they well up.
Photo 13- Discharge riverbed of the Orientales wetland, 400 m downstream from its headwaters (View to the SW).
Photo 14- Waterfall in the discharge riverbed of the Orientales wetland, 300 m upstream from where it joins the Cajón tributary.
Photo 15- Junction point of water conveyance channels from the Cajón and Orientales wetlands.
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Furthermore, in the Cajón wetland it is impossible to identify a specific sector from which the waters emerge. The abundant growth of phreatophyte vegetation, forming “cushion” type traits, does not allow locating with certainty the actual point or points where the waters originate (Photo 16).
It appears that the upwellings are concentrated around an area located in the Western end of the wetland, where a semi-swampy environment predominates. It appears that the waters would spring up along the plane or interface between two banks or ignimbritic strata having different permeability, that more or less coincide with the surface area of the flood plain in the sector. The presence of a tube stuck in the central portion of the wetland, from whose end (0.5 m above the surface) a fluency or upwelling is recorded, gives an indication that in the sector, the subsurface water dynamic is subjected to a certain hydraulic load. Said load controls and facilitates the flow of water to the surface, providing a constant, permanent feed to the wetland.
As a result of this singularity, it is possible to assume that – in the past – the waters would also have run with the same regularity and flow as they do in the present, beyond the intervention of human beings (collection and conveyance works). In its entire extension, one observes that the surface section of the Cajón wetland is saturated with water. Favored by the local slope, the waters feed a nearly straight riverbed which, after running about 300 m, leads them to the West to join the discharge riverbed of the Orientales wetland (Fig. 4 and Photo 15).
The waters that currently feed both wetlands, that are meteoric in nature, would have their origin in the East and Southeast side of the Inacaliri or Cajón volcano [Cerro Inacaliri o del Cajón], related to rain or snow events during the so-called “Bolivian winter”. In a way, the described nature can be demonstrated by the results of the chemical analyses made on two water samples taken from the Intakes C-1 and C-3, on the riverbed of the Silala River. The dissolved solids reach values that range between 95 and 149 mg/l, respectively, indicating relatively young waters, with little “residence time” and therefore having limited capacity to interact or dissolve the minerals that are part of the composition of the rocky or sedimentary materials that contain them.
From the point where the waters of the Cajón and Orientales wetlands join, approximately 700 m East of the Chile-Bolivia border, the waters give rise to the main riverbed of the Silala River, which flows at the bottom of a deep, narrow ravine, carved in ignimbritic sequences. Some authors apply the term “gorge” to denominate this morphological feature (Araya, op cit.). The assumption is that those volcanoclastic materials used to form continuous sequences that covered the entire sector where the ravine is currently located (Fig. 4 and Photo 17).
As a watercourse carries more volume of water, there is a significant drop in the ratio between the friction surface and the riverbed section. What happens is that the energy, previously dissipated by effect of the friction against the walls, would then be used to increase the flow velocity, causing the erosion of the riverbed and a decrease in the gradient in the segment that follows downstream from the junction.
Photo 16- Sector of the Cajón wetland,
with the typical phreatophyte vegetation forming ‘cushion’ structures.
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In the 4.6 km segment comprised between Intake C-2 of FCAB in Chilean territory and the CODELCO Intake, the Silala River runs through a narrow (0.30 to 0.40 m in average), winding and well-developed riverbed (it maintains its transverse profile), carved in an old flood plain, with abundant cover of phreatophyte species. The average slope of the hydraulic centerline is in the range of 3.9 – 4.9% (in an unlined channel, the water runs with a slope of 0.02%). Slight focalized narrowings can be attributed to obstructions linked to the fall of voluminous rocky blocks from the steep sides of the ravine. Throughout this trajectory, only two tributary ravines reach its riverbed: from the left bank, Quebrada Negra, and from the right bank, Quebrada Inacaliri (Fig. 4)
At about 2.3 km downstream from the CODELCO Intake, the Silala River (Fig. 4) gradually and steadily leaves its canalization at the bottom of a deep ravine, joining the discharges of the Queñuagual or Quebrada Cabana; emerging to a flat, low terrain which corresponds to the high part of the San Pedro River basin. From this point, predecessor streams to the current Silala River conditioned the development of a vast alluvial cone, whose apex is located around the point where the ravine loses depth. After exiting the canyon, the stream is no longer confined and both the depth and the gradient decrease suddenly; with which the liquid course cannot continue to transport its entire load. The referred structure corresponds to a typical morphological and depositional feature that is peculiar to the terminal segment of most of our highland ravines or rivers, where changes in the local slope of the terrain determine that the surface waters favor percolation over runoff. Lastly, a significant part of the percolated waters together with a series of lateral inflows -which correspond to surplus non-collected inflows from the Colana and Cabana ravines- flows subsurface to the West and emerges in a depression zone called Ojos of San Pedro, where it is collected by CODELCO by means of a series of drains. The volumes of flow harnessed here fluctuate between 680 and 800 l/s.
It is assumed that at present the discharge riverbed of the Silala River throughout a trajectory of about 7.0 to 7.5 km, from its beginning in the Cajón and Orientales wetlands (4,350 to 4,500 m.a.s.l.) to the discharge zone in the headwaters of the San Pedro River basin (4,150 m.a.s.l.), has reached a relatively balanced profile: it does not induce erosion or deposition. The waters run at a moderate rate, clean, crystalline. Three factors contribute to emphasize this situation: a) inclusion of a settling pond or tank in the FCAB intake structures, C-2; b) stonework lining in the segment of the Silala riverbed comprised between the confluence of the Cajón and Orientales in Bolivian territory and the present FCAB Intake in Chilean territory, C-2 (Fig. 4); and c) abundant growth of phreatophyte vegetation around important segments of the transport section of the Silala River.
It is estimated that, for the most part, the current feed system of the SHRS continues to be linked to the inflow of waters generated during the so-called “Bolivian winter” (rains and/or melting of ice/snow). It is reckoned that, just as it happens in other sectors of our highland area, the local rainfalls are strongly influenced by orographic factors (morphological features and height).
Photo 17- Sector of old Intake C-1 on the Silala River in Bolivian territory,
including the junction of the Orientales and Cajón tributaries.
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At present, near the confluence point of the Orientales and Cajón tributaries (130 m upstream from Intake C-1), in Bolivian territory, the mean base flow of the Silala River is approximately 160 l/s. Out of this total, about 100 l/s would correspond to inflows from the tributary that has its origin in the Orientales wetland, and the remaining 60 l/s, to waters from the tributary that has its origin in the Cajón wetland.
Appraisements done with some discontinuity during the period April 1969 – September 2000 in the riverbed of the Silala River, around the Chile-Bolivia boundary, have provided average values of 182 l/s (Vidal, 2000a).
For the sector corresponding to the headwaters of the Silala River basin in Bolivian territory, the average annual specific yield has been calculated at 2.01 l/s/km2 (Vidal, op cit.).
Regarding the potential of underground waters associated with the Silala River basin, it is worth noting that there is knowledge of only two exploration drillings made close to 1999 around its riverbed, 150 m downstream from the boundary with the Republic of Bolivia. The probe S-1 reached a depth of 62.0 m, while S-2 reached a depth of 70.0 m; the results of their respective pumping tests showed flow rates of 60.0 and 115.01 l/s, respectively (CAPTAGUA, 1995a, and 1995b).
The analysis of the materials traversed in S-2 reports on the existence of a granular sequence, typical of fluvial to fluvio-alluvial processes, (riprap, gravels, and sands) 58.0 m thick. Both probes recorded slight upwelling, attributed to the confinement effect caused by a surface level of about 10.0 m thick, having a higher content of interstitial clay. It is assumed that the recharge mechanisms of the local aquifer system, contained in the sedimentary filling of the Silala River ravine, would mainly respond to inflows linked to the typical rainfall patterns of the highland region, concentrated during the so-called “Bolivian winter” (from December to March). This singularity favors the recharging of the waters, taking into account that after becoming saturated with moisture from the first rains, the soil keeps part of the moisture for the subsequent rains. The recharges that are concentrated in the Cajón and Orientales wetland areas -located in Bolivian territory- occur through granular sedimentary materials having primary porosity, as well as by fracturing and/or alteration, secondary porosity, in ignimbritic rocks. It is assumed that a predominant proportion of the recharge waters would come from percolations of pluvial or pluvio-nival waters, to very porous colluvial sequences, that cover with discontinuous thicknesses the South and Southeast sides of the Inacaliri volcano [Cerro Inacaliri o del Cajón]. Around both wetlands, the flat morphology of the terrain would decisively favor the percolation of rain waters to the deep levels.
According to parameters provided by the General Directorate of Water (1987), it is possible to make calculations that give indications of the attractive hydrogeological potential contained in the sedimentary filling of the Silala River valley around the boundary with the Republic of Bolivia: a) for the hydro-meteorological station installed in the premises of the CODELCO Intake C-3 at 4,100 m.a.s.l., it records an mean annual precipitation of 112.2 mm; and b) applying a correction for altitude, for the area of the headwaters of the Silala River basin in Bolivian territory, at 4,300 m.a.s.l., it is possible to assign a mean annual precipitation of at least 200 mm. Thus, for a basin having a surface area of 80 km2, a rainfall of 22 mm/year, and a 20% percolation of the water that fell, one obtains:
that would correspond to a mean annual flow rate, which passes through a section of sedimentary filling of the Silala River valley around the Chile-Bolivia boundary area.
Based on the preceding background information, it is reckoned that the Silala River valley, in its Chilean section, possesses a voluminous granular sedimentary filling that is very favorable for containing significant renewable resources of underground waters, subjected to effective permanent recharges from the regional climate regime.
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EVOLUTION OF THE RIGHTS AND MODALITIES OF THE EXPLOITATION OF THE SHRS WATER RESOURCES
At present, the SHRS resources are only used for diverse purposes by Chilean companies (FCAB and CODELCO). The capacity to be used is linked to a series of factors: a) favorable topographic and flow characteristics in the intake area; b) steadiness of the volumes of flow; c) good physicochemical quality of the waters; and d) sustained demand of the resource for diverse uses, such as mining, industry, potable.
In the Bolivian sector, however, diverse causes hinder or limit an effective or permanent use of the waters of the SHRS: a) unfavorable topographic characteristics around the area of possible intakes; b) little to no demand for the resource due to the absence of or distance to populated centers and low number of mining, industrial, livestock, farming, and recreational activities; and c) forced or necessary energy requirements to collect and direct the collected waters to possible consumption or use centers.
Around 1906, in view of the availability of an attractive surface flow rate of waters passing by sections of the riverbed of the Silala River around the Chile-Bolivia boundary, the company “Antofagasta (Chili) and Bolivia Railway PLC” (FCAB, in Spanish) was granted by the Chilean authorities the rights to utilize it. The concession was approved on November 30, 1925, through Decree No. 194, recorded in the Water Rights Record of the Irrigation Inspection of the General Directorate of Public Works under the Ministry of Public Works. By virtue of the entry into force of the new Water Code on October 1981, FCAB proceeded in November 1989 to regularize said exploitations for a flow rate of 20,500 m3/day (237 l/s), according to the permanent and continuous consumptive modality.
On September 23, 1908, the same company obtained from the authorities of the Republic of Bolivia a new water right over the same river. The concession does not indicate flow rate; it merely sets down the need for “…leaving one third of the collected water for those who wish to use it afterwards…”
Between 1908 and 1910, as a way of improving the intake and conveyance conditions of the waters to be exploited, FCAB began construction of some civil works: the company recorded two structures corresponding to elements of collection, storage/ settling, and conveyance pipelines. One of them was installed in the riverbed itself of the Silala River, about 50 m downstream from the boundary, Intake C-2 (Photos 17 and 18); and the second, approximately 480 m upstream from said boundary, Intake C-1 (Fig. 4 and Photo 19).
Toward 1928, taking into account considerations linked to the need of guaranteeing the physicochemical character and especially the bacteriological character of the collected waters – given their potable purpose, the FCAB, with the authorization of the Bolivian authorities, began construction of additional works. The company specially included some hundreds of linear meters of ditches or drains (equipped with sections lined in part or in full with masonry of local stone), aimed at improving the intake conditions around the points where the
Photo 18- Former Intake C-1 of FCAB in Bolivian territory, no longer in operation.
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waters emerged in the springs or Cajón or Orientales wetlands, and to accelerate surface runoff. The collection of Silala River waters around their respective points of surface-origin at both wetlands, together with the improvement of the runoff conditions, turned out to be very effective in that they minimized the contamination risk associated with harmful element or substance dissolution mechanisms – from the original natural riverbed- as well as with the intervention of organic wastes of animals that went to drink at said springs or wetlands (organisms like coliforms and heat resistant coliforms).
In the case of the Orientales wetland, in particular, the intake structures set down a series of ditches or drains having linear development, according to a typical geometric “herringbone” layout, concentrated around the Northeast side of the spring or wetland, coinciding with the area where the surface manifestations of waters (water source, spring, “ojos” [water holes]) recorded the maximum flow rates (Photos 11 and 12). The ditches, mainly carved in pink ignimbrite rocks, ultimately discharge into a collecting canal that has a mean width of 1.0 m and a mean depth of 0.30 to 0.40 m. In the case of Cajón wetland, the collecting canal has a mean width of 0.40 m and a depth of 0.30 m. Favored by the morphological conditions of the terrain, these structures ultimately flow together in a single conveyance canal (Fig. 4 and Photos 15 and 17). Only in certain segments does the complete section of the structure have some kind of lining (a type of stonework), built from tabular pieces of ignimbritic rocks (like actual ‘flagstones’).
As a result of this, the riverbed of the Orientales tributary, before joining the Cajón tributary 330 m upstream from Intake C-1, flows at the bottom of a deep, narrow gorge, flanked by vertical walls having average heights that range between 12.0 and 15.0 m (Fig. 4 and Photos 17 and 20). The verticality of the walls together with the geomechanical nature of the materials of the ignimbritic sequence, have caused the fall of voluminous blocks towards the riverbed - in a position of obstructing specifically the runoff – plus a strong differential erosion capable of forming small waterfalls or rapids (Photo 20).
In the 330 m stretch comprised between the junction point of both tributaries and the original intake in Bolivian territory, Intake C-1, the conveyance canal presents its section fully lined with stonework (Fig. 4 and Photo 18).
At the Cajón wetland or spring, however, the works designed for improving the collection and conveyance of the naturally emerging waters, consist in a semi rectilinear canal, about 610 m long; some minor drains flow obliquely into it. Along this stretch, only in certain segments does the riverbed include stonework lining.
The record of the individual water inflows of each of the described wetlands makes it possible to establish that the smaller volume of water corresponds to the Cajón wetland. This singularity appears to be linked more to the little-to-no maintenance of the works (cleaning or extraction of remains corresponding to phreatophyte species and/or sediments, both from the drains and the conveying canal),
Photo 19- Intake structure C-2 of FCAB.
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than to a smaller natural yield of the respective water sources that make up the wetland.
The surplus from the Silala River, downstream from Intake C-2, together with certain flows associated with “recoveries”; springs with an estimated flow rate of 130 – 140 l/s, are collected by the Chilean Copper Corporation (CODELCO, in Spanish) by means of a special structure built in the bed of the Silala River, Intake C-3, around a point located 4.6 km downstream from Intake C-1 (Fig. 4 and Photo 21). The operational efficiency of this intake structure determines that the present riverbed of the Silala River, downstream from this point, shows little surface runoff except during the rainy season associated with the so-called “Bolivian winter” (between December and March). At this time, the waters tend to create an area with moist terrains known as the Ayaviri water meadows, around a point that corresponds to the headwaters of the hydrographic basin of the San Pedro River.
The inflows of the “recoveries”, have subsurface access to the main riverbed from numerous points, the sum of which is seen at Intake C-3 of CODELCO (Photo 21). The waters favor the development of springs located at the foot of the rocky bluffs that delimit the present bottom or bed of the Silala River. They can be identified by the localized presence of abundant phreatophyte vegetation which gives the terrain a semi-swampy character (Photo 21). Most of them are found around the North and Northwest side of the riverbed, concordant with areas where there is an increased fracturing in the rocky sequences involved in the Cabana Ignimbrite. This singularity makes it possible to assume that a large portion of the inflows that feed the springs in an underground manner, may come from percolations of pluvial or nival surface waters that originated around the South side of the Inacaliri or Cajón volcano (Fig. 4). The examination of satellite images of the sectors allows observing the presence of a saturated area (according to a similar hue to the one presented in the Cajón and Orientales wetlands) around the confluence point of Quebrada Incalairi (sic) with the Silala River, upstream from Intake C-3.
This singularity grants the Silala River the character of an effluent river. With regards to superficial inflows, the larger ones would be associated with Quebrada Negra and Quebrada Inacaliri; the first having its origin in the West side of Volcán Silaguala, the second, in the South side of Inacaliri or Cajón volcano [Cerro Inacaliri o del Cajón]. In both cases the inflows would be linked to small hydrographical basins, mainly involving terrains located in the territory of the Republic of Chile. The primary origin of this water would correspond mainly to percolations from the melting of
Photo 21- General view of Intake C-3, CODELCO.
Photo 20- Section of the Silala ravine, 500 m downstream from the intake.
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snow that fell around the highest rock mass during the so-called “Bolivian winter”.
On May 14, 1997, the competent Bolivian authority, decided unilaterally to declare null the concession that had been granted to FCAB in connection with the surface runoff waters of the Silala River, in Bolivian territory. In practice, this operation was materialized by removing a special structure that historically allowed the entry of the waters into a regulation tank and, later, to the conveyance elements towards Chilean territory (Photo 16). As a result of this decision, at present the surface runoff waters of the Silala River – after passing over the original Intake C-1, in Bolivian territory - naturally flow to Intake C-2, in full operation, located in Chilean territory, triggered by the favorable local gradient of its hydraulic centerline. At this point, the waters are collected and conveyed by a metal pipeline to the exploitation sites, in conformity with the rights legally granted by the Chilean authorities of the General Directorate of Water Resources (DGA) under the Ministry of Public Works.
In strict conformity with a series of technical arguments, the competent authorities of the Republic of Bolivia, through the Prefecture of Potosí and via Administrative Resolution No. 71/97 of May 14, 1997, declared null and void the concessions for the use of the waters, which had been granted in favor of the Chilean company FCAB.
As of this unilateral decision, in early 2000, the respective Bolivian authorities decided to grant the concession of all the surface waters of the Silala River via public tender, adjusting this to a mean flow rate measured around the crossing point located immediately upstream from the boundary with Chile. Through Administrative Resolutions No. 15/00 and 20/00 of March 15 and 31, 2000, respectively, the Superintendency of Basic Sanitation declared the proponent DUCTEC S.R.L. (LLC) as concessionaire of the Public Tender for the 40-year concession of the use of the waters. According to the Reference Terms of the Concession, the use of the waters of the “Silala springs” set down “… the industrialization, commercialization in or out of the country and its transportation by means of channels, pipelines or packaged in bottles or demijohns, provision of potable water, etc…” (Superintendency of Water Resources, 1999 and 2000).
MORPHOGENESIS OF THE HYDROGRAPHIC BASIN SYSTEM OF THE SILALA RIVER
Next is an analysis of the processes and mechanisms that would have determined the origin, genesis and evolution of the SHRS (hydrographic basin of the Silala River).
As a result of the particular climatic, geological and tectonic conditions, a large part of our highland area that borders with Peru, Bolivia and Argentina corresponds to a territory that has been morphologically compared in both meridional and latitudinal aspects. The so-called “Andean orogeny” would have exerted the most influence, concurrent with the final uplift of the Andes mountain range, towards the end of the Tertiary Period and beginning of the Quaternary Period.
In the area it is possible to recognize a marked relationship between tectonics and magmatism, from the moment in which the main eruptive centers are located, along a series of alignments or important faults at regional level or slightly on the fringe thereto (Fig. 2). This singularity determines that the interaction between the eruptive (volcanic activity) and tectonic (deformations and faults) processes, mainly, would have been key for controlling the development or formation of the local hydrographic system. The arid environment would have been decisive for imposing a characteristic slowness in the fluviatile processes that began as of the Upper Miocene. Significant changes in the climatic regime may have taken place in connection with Pleistocene glacial phases or cycles, at which time the snow line would have registered remarkable descents.
Around the headwaters of the Silala River is an important center that emits pyroclastic materials (Pastos Largos caldera, in Bolivian territory), whose emissions in phase have generated one of the most extensive tuff and ignimbrite fields of the continent, which for the most part are involved in the shaping of the “lowlands”.
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The climatic environment of the highland area makes it possible to note that the region is associated with a morpho-climatic medium of mechanical domain, with predominantly thermoclastic processes. The level of aggressiveness is expressed in the development of powerful covers of fragmentary materials made up of strong accumulations, colluviums, integrated by small pieces of rock.
The dynamic of the surface runoff of waters becomes a powerful natural agent that intervenes or controls a significant portion of the morphogenetic processes; this situation does not stand out at first glance, taking into account that the processes involved do include very slow and hardly spectacular changes.
The factors that control the erosive activity or capacity of surface runoff include: the slope of the relief, the intensity and annual distribution of rainfall, the geomechanical character of the terrain (soils or rocks), and the presence and characteristics of the plant cover. In the case of interest and for the purposes of this analysis, these last two factors gain special importance. The absence of plant cover plus the marked seasonality of rainfall are decisive in favoring the effects of water erosion; both factors are peculiar to our highland area. The local rainfall patterns associated to the so-called “Bolivian winter” determine that approximately 95% of annual rainfalls are concentrated in only three months (January to March). As a result thereof, the amount of water that flows in the form of surface streams is much greater than that of areas in which the rain is spread out equally throughout the whole year; this singularity conditions a notable increase in the water erosion potential, directly associated with the capacity for shaping ravines or valleys that are able to shape depression zones to contain wetlands and beds of streams, brooks or rivers.
Now, referring specifically to the interests of the present study, the concept of ‘river’ involves a stream of water having a uniform, successive and permanent system (De Pedraza, p. 199, 1996). Strictly speaking, it deals with surface runoff systems that collect, convey and discharge in a linear way the waters that flow in from springs or water sources, as well as from elevated terrains that are subject to pluvial, nival or mixed precipitations.
From a geomorphic viewpoint, the generalized use of the term ‘valley’, when associated to a fluvial domain, is linked to structures that correspond to a confined linear corridor, having a varied bottom (flat or concave) and carved by the direct action of the currents throughout its entire evolution (De Pedraza, 1999, p. 221).
In some Andean environments of the highland area, the first phases of the shaping answer to a glacial-type erosive activity that occurred as of the Quaternary Period (1.8 to 2.0 million years BP), at which time voluminous, active ice and snow caps covered vast sectors of the high summits. Glacial ice is compact and, strictly speaking, rigid; this determines its extraordinary erosive capacity for shaping valleys, depressions, hills and plains, whose effects at present are expressed in the development of singular morphological traits linked to weathering mechanisms (striations, glaciated rocks) as well as in a series of conspicuous depositional structures (moraines, erratic blocks, drumlins, eskers, kames, alluviums).
In the highland area, the pluvial waters that are not retained by the thin soil cover (alluvial or colluvial) or superficially fractured and/or altered rocks, (intercept waters) and that exceed the percolation capacity of the terrain; upon gaining access to depression areas may create temporary or permanent lagoons. If the waters retained there do not evaporate and the inflows continue, they will exceed the storage capacity, beginning their flow to topographically lower areas; this mechanism is expressed by the creation of watercourses that are precursors to rivers, ravines or brooks.
By virtue of their respective ages, the volcanoes tend to present numerous linear incisions in their sides (radial ravines) as well as rounded cones, a situation that allows attributing them to the “older” eruptive cycles. Other “younger” domes and lava flows show morphological traits associated to frankly glacial – and therefore modern - erosion which, according to their respective forms and surface hues, determine the development of showy and unmistakable morphological traits (Lema & Ramos, 1996).
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Regarding the area of interest, what stands out is a voluminous flow of dark lava, andesitic to basaltic andesite in nature, located around the West side of the depression sector that is occupied by the Cajón and Orientales wetlands. Said lava flow originated in the crater of the Inacaliri o del Cajón volcano [Cerro Inacaliri o del Cajón] (5,529 m.a.s.l.); after spilling down the East side, it flowed towards the Southeast, in the form of a voluminous tongue having a lobular front, until reaching, covering and partially occupying a small preexisting depression zone (Fig. 4 and Photo 10). It is assumed that in the sector corresponding to the present surroundings of the Cajón and Orientales wetlands, the flow in question would have induced a significant change in the original local runoff pattern.
The origin of these structures would be linked to various eruptive cycles that took place between the Lower Miocene and the Holocene (Marinovic & Lahsen, 1984; and Ramírez & Huete, 1981; and Mortimer, 1980).
It is estimated that the present hydrographic basin system of the Silala River at its Bolivian headwaters would have developed as of the Upper Miocene (4.5 to 4.8 million years BP), at which time the territory would have attained a shape quite similar to the current one. According to Abele (1991), during the first phases of the Quaternary shaping, the scant availability of water in a hyper-arid environment would have only allowed the development of an incipient drainage system –dendritic- that was consistent with, concordant with or controlled by the regional incline of the terrain and expressed in the development of riverbeds with limited vertical incision and incipient erosive activity, on primitive volcanic cones and on the shaping of ignimbritic plains (Bloom, 1999, p. 286) (De Pedraza, 1999, p. 334).
During the Pleistocene (from 1.8 to 2.0 million years BP), the area was partially covered by glacial caps more developed in the spring Este de los Andes. This is in response to persistent contributions of moisture from the interior of the continent (Romero et al., 1991, p. 87).
The glacial activity, acting on the preexisting morphology in a undoubtedly volcanic environment, would have played a decisive role on the shaping of the primary traits of the SHRS, with prevalence of an incipient drainage system made up of a series of linear courses having short trajectories, little depth, and short-lived or seasonal runoff.
Later, it is assumed that the local slope of the terrain would have favored the capacity of erosion or competence (understood as the capacity to transport sediments) and the effort of surface runoff (load capacity limit). By reason of the steep local slopes and the consequent great energy of the flows, the original incisions would have only been accentuated around the sides of some larger volcanoes and in some segments of depression zones and/or narrow passes.
In response to the prevailing climatic conditions, the pluvial waters – in an environment with more moisture than the preceding and even the present one – after running and concentrating in local depression areas (shaped from vast plains constituted by ignimbritic deposits) would have only favored the focalized development of incipient closed, endorheic or centripetal initial basins. Later, at local level, some of them would have then evolved into actual lagoons, that at present lack permanent waters, even though they continue to receive that denomination: for example, Blanca and Chica, in Bolivian territory.
It is assumed that as of the 19th Century, a gradual rise in temperature would have determined a definite retreat of the ice – snow masses or caps that marked out the highest summits of volcanoes and hills in the sector. In terms of the levels of rainfall, evaporation and moisture of the air, the climate tended to evolve toward a regime that is very similar to the present one; this translated in fewer inflows or availability of surface waters to the existing or established water systems. In response to this climatic mechanism, the SHRS in general and the original Silala River in particular, would have experienced a significant drop in volume of flow. This explains the fact that the valley containing the riverbed of the Silala River possesses a transverse profile that in transport capacity completely surpasses the present flow-through (Photos 12, 15, 16, and 17).
Meanwhile, the waters accumulated in depression zones, high Andean lagoons, would have begun to decrease in volume, reducing their area expanse (Blanca and Chica). The presence
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of some local lagoons having linear and concentric morphological traits, genetically linked to remains of paleo-lines of beaches, constitute irrefutable signs of this mechanism; the described traits are fully identified in satellite images at a 1:50,000 scale (Landsat Image TM5 233075RGB741), on the banks of the Khara lake, located in Bolivian territory, 17.0 km Northeast of the point where the Silala River enters Chilean territory.
Its present mechanisms of seasonal recharges or feed are linked to surface runoff waters, concentrated during the so-called “Bolivian winter” (from December to March). After a temporary storage, almost all of the waters evaporate. On the surface, in the Southwest side of the Orientales wetland, it is still possible to identify the presence of fine materials, clayey silts, whitish, powdery, saline, remains of sedimentation processes in a frankly lacunar to pseudo-lacunar environment.
Over time and particularly during the Late Glacial – Early Holocene (10,400 to 13,500 years BP), coinciding with the maximum moist phase of the highland area between 22° and 24° S, an active rain cycle with marked descent of the evaporation begins, due to an increase in regional cloud cover (Gey et al., 1999, p. 243; and Grosjean et al., 1999). Palynological and paleo-edaphological evidence from pollen found in highland wetlands and/or peat bogs, lacustrine sedimentology, and human settlement history all indicate that in the region there would have been rainfalls equivalent to double the present ones, that is, in the range of 180 – 200 mm/year.
This would have determined the start of a fluvial dynamic of great competence, favored by the local slope and by the presence of impermeable terrain, able to accelerate the runoff. Consequently, the primitive drainage system rapidly evolved into a more mature system. Isotopic studies make it possible to determine that in the high Andean area in Northern Chile, this rain cycle generated a large portion of the present recharge of the main aquifer systems that exist there (Grosjean et al., 1995, p. 250); the great availability of water increased the surface runoff, favoring the deepening of preexisting or primary riverbeds.
In essence, due to the changes in the preexisting climatic patterns, the greater availability of concentrated runoff water would have determined a substantial change in the primitive hydraulic variables, compatible with the need of evacuating the larger volumes of flow.
At SHRS level, the necessary increase of the respective transport sections would have materialized through a deepening and widening of the preexisting riverbed of the Silala River.
The local slope and morphology, together with the presence of superficial cooling cracks in the ignimbritic sequences, determined that the waters developed a natural, concentrated forced flow with discharge or spillage toward the West until reaching depression grounds that are currently occupied by the “ojos” (water holes) or wetlands of San Pedro, in Chile.
The flow energy, helped by the slope of the original hydraulic centerline, together with favorable, constant pluvio-nival recharges, determined that the Silala River not only developed a discharge riverbed having a semi-rectilinear trace, but also acquired the condition of being permanent. As a result, the original SHRS having a closed or endorheic nature evolved into an exorheic one, a situation that endures to the present day. In keeping with this nature, the hydrographic basin of the Silala River allows it to be encompassed in the categorization of a typical highland exorheic basin.
The gradual and persistent deepening of the ravine that contains both the present main discharge riverbed of the Silala River (in Chilean and Bolivian territory) and its Orientales and Cajón tributaries (exclusively in Bolivian territory), gave shape to a structure having a typical rectangular section that is characteristic of rivers having a tranquil or hardly varying dynamic, carved in sub-horizontal stratified rocks (breccia and ignimbrites) (Photos 15, 16, and 18). In keeping with the local slope, the runoff –associated with a rapid flow – would have determined a greater capacity of erosion and sediment transport, with the consequent increase in roughness and depth of the respective transport sections, reductions in the slopes and velocities, with a tendency to restore the original slow, tranquil flow.
Strictly speaking, the present pattern of the shaping of the Silala River corresponds exactly to an example at reduced scale of most of the main river systems in Northern Chile. In all cases, the character of river is given by: a) natural and successive flow or stream of waters from a higher to a lower level; b) relatively uniform volume of flow; c) the transport of material
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by the water is carried out along a narrow, winding riverbed contained at the bottom of an irregular flood plain that is limited by subvertical rock wall (Fig. 4 and Photo 12).
The described shaping, unquestionably associated to fluvial to fluvio-alluvial processes, under similar morphological and geological conditions is peculiar to most, if not all hydrographic systems in arid zones, in the Coastal mountain range, the East side of the Pampa, and the pre-highland and highland areas of Chile, from at least the First to the Fourth Regions; irrefutable examples thereof are the ravines of Azapa, Lluta, Camarones, Vitor, Suca, Camiña, Retamilla, Tarapacá, Aroma, Chacarilla, and Guatacondo, among others. A large portion of these include riverbeds that are contained in ravines having deep incisions.
Around the specific area of interest, it is worth mentioning the typical traits of fluvial shaping of the present riverbeds of the Loa, Salado (with its tributaries Linzor, Toconce, and Caspana), San Pedro, Grande, and Vilama Rivers, etc. The Loa River in particular offers a clear testimony of a fluvial shaping in arid zones of our country.
We are evidently dealing with drain styles or traits that are not exclusive or peculiar to our Andean area. On the contrary, worldwide, the geomorphological literature records numerous examples of fluvial shaping in arid or semi-arid zones, definitely similar to those characteristic of the Silala River. In that regard, there are very good examples cited and described in multiple references corresponding to studies that were conducted in Peru, Bolivia, Argentina, Mexico, USA, Spain, Morocco, South Africa, Israel, Turkey, Australia, etc.
From a genetic viewpoint, most of the valleys and deep, narrow ravines – such as the one that contains the present riverbed of the Silala River- that are located in arid zones in Chile as well as in many countries worldwide, have their origin in rapid, large water flows.
The volume of flow is controlled by basins having effective efficiency, during very intense rain cycles or episodes that occurred in the geological past, while the runoff energy, having high erosive power, responds to favorable morphological conditions (steep slope of the hydraulic centerline) (Fig. 8).
In order to confirm the definitive fluvial nature and origin of the present shaping that contains the riverbed of the Silala River, both in Bolivian and Chilean territory, we resorted to analyzing the sedimentary materials extracted from various trial pits between 1.5 and 3.0 m deep, excavated in the edges of the present riverbed as well as around the Cajón and Orientales wetlands (Fig. 4). The record of the sedimentary sequences traversed in the trial pit allowed establishing the presence of granular deposits like riprap, gravels, and sands, in few interstitial fines, with dominantly volcanic clastic elements, homo-compositional (andesites and basaltic andesites), unaltered, resistant. Said deposits show characteristics of rounding and sphericity that are peculiar to deposition in an unmistakable fluvial to fluvio-alluvial environment (Photos 2 and 3).
In addition, the presence of hetero-compositional, faceted or striated clasts, incorporation of large blocks, or clear sedimentary traits, typical of glacial-type genetic mechanisms, as the Bolivian party maintains, was not identified in the extracted materials.
Morphological traces that are peculiar to
Fig. 8- Profiles by hydraulic centerline of the Silala River.
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glacial activity can be identified in the South and Southeast side of the Cajón or Inacaliri volcano, genetically associated with small morainic remains, even though they can also be attributed to mass wasting processes: landslides, solifluction, and block or debris flows.
CONCLUSIONS
The totality of the preceding background information makes it possible to determine, unmistakably and contrary to the thesis maintained by the Bolivian party, the existence of the Silala River. It is a river whose headwaters and discharge riverbed have been carved in volcanoclastic, ignimbrite sequences. Its sources, corresponding to two typical highland wetlands (Cajón and Orientales), are located in Bolivian territory mainly fed by underground flows that are situated in volcanic rocks, associated to a voluminous lava flow. Having originated in the crater of Inacaliri or Cajón volcano [Cerro Inacaliri o del Cajón], they ran down its South and Southeast sides, covering preexisting ignimbritic sequences. The two wetlands total a surface area of about 11.0 hectares. The local morphological traits, associated to slopes towards the West, grant the river a consistent character with a natural discharge or runoff to Chilean territory, peculiar to an exorheic basin of our highland area.
The significant energy with which the waters surface in both wetlands demonstrates the existence of hydrodynamic conditions controlled by a certain hydraulic load. Therefore the intake works (drains, channels, and linings) that were made towards the beginning of the 20th Century in both wetlands as well as in important segments of the discharge riverbed do not exert any action whatsoever as to forcing said flow. As a result thereof, after welling up in both wetlands, the waters run in a successive, natural and continuous manner toward Chilean territory. Furthermore, around the periphery of both wetlands, it is not possible to identify the presence of remains of morphological (palaeo-levels) or plant traits, linked to drops in water levels, induced by civil works built to optimize the exploitation of the surface water resource. In keeping with the morphological character of the terrain around the Cajón and Orientales wetlands, stems the conviction that the local slope of the terrain is absolutely sufficient for the sum of the upwelled waters to naturally run to the West (Chilean territory), by means of a successive and continuous course (the Silala River).
In connection with the Bolivian thesis that maintains that the interventions made in the area occupied by the Cajón and Orientales wetlands would have been essential to force the runoff of the waters from an endorheic basin toward Chilean territory, it should be pointed out that according to the local geomorphological, geological and hydrogeological environment, such actions would have had to record: a) mechanical impulse or elevations, pumping; and b) complex canalization systems which incorporate alternatives of cuts and/or tunnels. Ruling out these procedures, from a hydraulic viewpoint, it is impossible for the waters of an endorheic basin to otherwise flow West (Chilean territory).
In keeping with what has been set out in the preceding point, stems the conviction that the interventions made towards the beginning of the 19th Century in the area of the Cajón and Orientales wetlands (drains and canalizations) would not have caused the effect of artificially forcing the runoff of the sum of the upwelled waters toward Chilean territory.
The Bolivian thesis maintaining that prior to the interventions made in the area of the Cajón and Orientales wetlands there prevailed an environment typical of an endorheic basin, must be conditioned to the presence of poorly drained terrains, that is, lacking in discharge and, therefore, favorable to the natural development of lagoons or salt flats. The observations made in the area have not allowed identifying traces or remains of this type of structures.
Based on the application of modern techniques, Vidal (2000) was able to establish that the reduction in evaporation generated by the civil works executed at the beginning of the 19th Century at the Cajón and Orientales wetlands -due to effects of reductions in direct evaporation and evapotranspiration- would have translated into the increase of only 3.0 % with respect to the original natural volume of flow of the Silala River.
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The waters of the Silala River run according to a riverbed contained in a ravine that has deep incision, whose drainage style is peculiar to the highland area. The decisive control that the volcanic activity exerts on the drainage determines that, from a genetic viewpoint, the majority of the ravines are categorized as “young” (later than the Upper Tertiary or Plio-Pleistocene Period).
The morphological and geological characteristics of the sector make it possible to establish that prior to the execution of the intake works, the Silala River waters – which originated in Bolivian territory – naturally ran to their natural discharge in Chilean territory. The hydraulic slopes (in the range of 3.9 to 4.9%) of the riverbeds that convey and discharge the waters that originated in the Cajón and Orientales wetlands, suffice to generate an effective, permanent and natural runoff toward Chilean territory, granting it the nature of a consistent river.
The significant and permanent lateral inflows that the Silala River receives along its discharge riverbed make it possible to rate it as an effluent river.
The singularity that the hydrographic headwaters of the Silala River are located in Bolivian territory make it possible to assign it an unmistakable character of a binational river and, therefore, possessor of a shared water resource.
For various reasons, at present the surface waters of the Silala River not only are the subject of exploitation on the part of two Chilean companies: a) the FCAB collects an average of 140 l/s, through a structure located near the Chile-Bolivia boundary; and b) CODELCO collects an average of 140 l/s, which includes the sum of significant “recoveries” (focalized springs), through an intake located at approximately 4.6 km downstream from the first.
At present, the Silala River presents a base flow that is quite constant over time, linked to a system of feed and regulation from two wetlands: Cajón and Orientales. At the point of entry into Chilean territory, the Silala River records a mean flow ranging between 160 and 180 l/s.
From a hydrochemical viewpoint, these are for the most part sodium bicarbonated waters having low to moderate levels of mineralization: 95 to 149 mg/l of dissolved solids (determined by evaporation), whose recharge would correspond to meteoric or modern waters genetically linked to the present local fluvio to fluvio-nival patterns. These waters have a pH close to neutral and slight excess of As content for potable purposes (ranging between 0.06 to 0.17 mg/l; the Chilean Potable Water Standard [NCh 409/1, Document 84] recommends maximum values of 0.05 mg/l of As).
REFERENCES
Araya, J. 2002. Análisis evolutivo de la cuenca del rio Silala, Plateau de la Puna, Norte de Chile. 10 p. National State Borders and Boundaries Department (DIFROL).
Baker M. C. W.; Francis, P. W. 1978. Upper Cenozoic volcanism in the central Andes. Ages and volumes. Earth Planetary Sciences Letters. Vol. 41; No. 2; p. 175-187.
Bazoberry, Q. A. 2003. El mito del Silala. Plural Editores. La Paz, Bolivia. 199 p.
Bloom, L. A. 1991. Geomorphology. A systematic Analysis of the Late Cenozoic Landforms. Prentice Hall, 532 p. New Jersey. USA.
Bruggen, J. 1950. Geología. Editorial Nacimiento; 509 p. Santiago.
CAPTAGUA Ingeniería S. A. 1995a. Informe Final. Construcción Pozo N° 1, Siloli. FCAB. (Unpublished).
CAPTAGUA Ingeniería S. A. 1999b. Informe Final Construcción Pozo N° 2. (Pozo 3102). Siloli. FCAB. (Unpublished).
De Pedraza, J. 1996. Geomorfología. Principios, Métodos y Aplicaciones. Editorial Rueda, 414 p. Madrid.
Gey, M.; Grosjean, M.; Nuñez, L.; Schotterer, U. 1999. Radiocarbon Reservoir Effect and Timing of the Late-Glacial/ Early Holocene Humid Phase in the Atacama Desert (Northern Chile). Quaternary Research. No. 52; p. 143-153.
González-Ferrán, O. 1994. Volcanes de Chile. Military Geographic Institute [Instituto Geográfico Militar, in Spanish]; 635 p. Santiago.
Grosjean, M.; Gey, M.; Messerli, B.; Schotterer, U. 1995. Late- glacial and early Holocene lake sediments, groundwater formation and climate in the Atacama Altiplano, 22°-24° S; Journal of Paleolimnology. No. 14; p 241-252.
Guest., J. E. 1969. Upper Tertiary Ignimbrites in the Andean Cordillera of Part of the Antofagasta Province, Northern Chile. Geological Society of America Bulletin. Vol. 80, p. 337-362.
Hauser, A. 1999a. Características geomorfológicas y geológicas del sector en torno a las captaciones de aguas superficiales en el valle del río Silala, límite con la República de Bolivia. Segunda Región. National Sub-
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Directorate of Geology. National Geology and Mining Service, 19 p. Santiago. (Unpublished).
Hauser, A. 1999b. Consideraciones hidrogeológicas en segmentos limítrofes del río Silala, Segunda Región. National Sub-Directorate of Geology. National Geology and Mining Service. 22 p. Santiago. (Unpublished).
Hauser, A. 2000. Modalidades de aprovechamiento: Marco geológico- tectónico- hidrogeológico- e hidroquímico. Morfogénesis y evolución del sistema hidrográfico compartido chileno - boliviano del rio Silala. National Geology and Mining Service. 57 p.
Lema, J. C.; Ramos W. 1996. Hoja Sanabria, Escala 1:100.000. National Geology and Mining Service of Bolivia. Geological Map of Bolivia. SGM Publication, Series 1 - CGB - 43.
Llibutry, L. 1956. Nieves y glaciares de Chile. Ediciones Universidad de Chile; 471 p. Santiago.
Marinovic, N.; Lahsen, A. 1984. Hoja Calama, Región de Antofagasta. Geological Map of Chile, No. 58, National Geology and Mining Service; 139 p. Santiago.
Mortimer, C. 1980. Drainage Evolution in the Atacama Desert of Northernmost Chile. Revista Geológica de Chile. No. 11; p. 3-28.
Portilla, G. F. Elementos de Geología. 1952. Editorial Aguilar; 653 p. Bilbao. Spain.
Ramírez, C. F.; Huete, C. 1981. Hoja Ollagüe. Región de Antofagasta. Geological Map of Chile, No. 40. Scale 1:250,000. Geological Research Institute [Instituto de Investigaciones Geológicas, in Spanish]. 47 p. Santiago.
Romero, H.; Rivera, A.; Fernández, P. 1994. Climatología en la Puna de Atacama y su relación con los recursos hídricos. Altiplano. Ciencia y Conciencia en los Andes; 455 p. Santiago.
Superintendency of Water Resources [Superintendencia de Aguas, in Spanish]. Sectorial Regulation System. Bolivia. 1999. Concesión de uso y aprovechamiento de los manantiales del Silala. Tender Documentation. (Unpublished).
Superintendency of Water Resources. Sectorial Regulation System. Bolivia. 2000. Contrato de concesión de uso y aprovechamiento de los manantiales del Silala. (Unpublished).
Vidal, J. F. 2000. Rio Silala. Memoria de visita a terreno. General Directorate of Water Resources. Ministry of Public Works. 7 p.
Vidal, J. F. 2000a. Rio Silala. Informe Hidrológico. (Draft Report). General Directorate of Water Resources. Ministry of Public Works. 47 p.
(Signature)
Arturo Hauser Y.
Geologist
Santiago, 20 of October, 2004
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APPENDIX B
PUMPING AND RECOVERY TESTS
1 PW-BO WELL
1.1 Pumping tests
A Variable-Rate Pumping Test (VRPT) or step-drawdown test and a recovery test were
conducted to determine the maximum long term output of the well. The well was
pumped at various rates increasing in steps with the aim of achieving stabilized
pumping levels. The test consisted of seven steps, ranging between 3 and 15 l/s. The
maximum pumping flow rate to reach a steady state was estimated to be 11 l/s.
The Constant-Rate Pumping Test (CRPT) involved measuring how the dynamic height
of the cone of depression evolved with a constant flow throughout the entire test to
determine the Transmissivity and Storage Coefficient of the aquifer. The analysis of the
results of the CRPT requires a variety of assumptions, not all of which apply. A
pumping rate of 10.8 l/s was used for the CRPT.
Pressure transducers were installed in both the pumped well, PW-BO and the CW-BO
observation well, and water level measurements were recorded digitally on a data
logger. Water levels were also measured manually throughout the testing.
1.1.1 Variable-Rate Pumping Test (VRPT) in Well PW-BO
The seven-step variable-rate pumping test was carried out on 29 November 2016 with
approximate flow rates of 3, 5, 7, 9, 11, 13, and 15 l/s (see Table 1-1 for a summary of
information). The test attained a maximum rate of 15 l/s. Notably, for the majority of
steps, the water level did stabilize. For the 15 l/s pumping rate, the drawdown was 46.27
m, and recovery to 90% took place in less than 5 minutes after pumping stopped. A pretest
pumping period was used to establish the steps for the VRPT, but water levels were
allowed to recover before starting the VRPT.
The results are plotted in Figures 1-1, 1-2 and 1-3. The figures show linear behaviour
over the first 20 meters of drawdown, which is consistent with the response of a
confined aquifer. This result matches what was observed in the field, where water was
found at 24 m depth in the Silala Ignimbrite and the water level rose to nearly 7 m.
The observation well was located 11 m away from the pumping well but even at the
maximum pumping rate had a drawdown of just 0.91 m. See Figure 1-3.
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2 Figure 1-1. Variable-rate pumping test in PW-BO well. Flow rate l/s Duration (min) Starting level (m.b.g.l.) Ending level (m.b.g.l.) Cumulative drawdown (m.b.g.l.) Head stabilization 3 120 8.76 14.46 5.7 Yes 5 240 14.46 15.67 6.91 Yes 7 510 15.67 20.55 11.79 No 9 330 20.55 24.22 15.46 Yes 11 360 24.22 29.53 20.77 No 13 270 29.53 41.1 32.34 Yes 15 110 41.1 55.03 46.27 Yes Table 1-1. Summary of variable-rate pumping test. 350
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Figure 1-2. Plot of pumping rate versus drawdown during the VRPT in the PW-BO well.
Figure 1-3. Variable-rate pumping test in the CW-BO well.
0
5
10
15
20
25
30
35
40
45
50
0 2 4 6 8 10 12 14 16
Drawdown (m)
Flow (L/s)
Pumping rate versus drawdown VRPT PW-BO Well
Annex II Appendix B
351
4 1.1.2 Constant-Rate Pumping Test (CRPT) in PW-BO Well The CRPT commenced on 1st December, 2016 at 10:30 a.m. with an initial static water level of 8.8 m.b.g.l. (meters below ground level) and pumping rate of approximately 10.8 l/s. The test lasted for 20.5 hours (Figure 1-4). When the test began, the water levels had fully recovered from the variable-rate pumping test. After approximately 13.5 hours of pumping (810 minutes), the water level stabilized at around 29.87 m.b.g.l., i.e. a drawdown of 21.07 m. Once the test was over, recovery was measured for 4 hours (240 minutes). The well recovered rapidly, reaching 90% of the pre-test level after 2 minutes. The observation well had a maximum drawdown of 0.59 m, but the water level did not return to the pre-test levels after 4 hours (see Figure 1-5). Figure 1-4. Recording water levels during the CRPT in well PW-BO. 352
Annex II Appendix B
5
Figure 1-5. Recording water levels during the CRPT in observation well CW-BO.
1.1.3 Estimating Transmissivity and Storage Coefficient from the CRPT results
Variable-regimen equations were used to obtain the elastic parameters of the aquifer,
assuming that all water comes from its own storage. To do so, the data from the CRPT
performed in the pumping well PW-BO and the observation well CW-BO and their
respective recovery tests were used (see location in Figure 1-6). It should be noted that
the observation well was 117 m deep, nearly 40 m deeper than the 80-m deep pumping
well PW-BO. The additional 40 m in the CW-BO well contained very friable rock and a
fault crossed the borehole (See SERNAGEOMIN, 2017), which may indicate a zone of
high transmissivity (see Figure 1-7).
Annex II Appendix B
353
6 Figure 1-6. Location of wells PW-BO and CW-BO. 354
Annex II Appendix B
7
Figure 1-7. Geological cross-section of the PW-BO, CW-BO, and MW-BO wells.
The results of the pumping test analysis for well PW-BO, were: transmissivity (T) =
450-1600 m2/d, permeability (K) = 8-17 m/d, and storage coefficient (S) = 2*10-4. The
analyses performed are summarized below.
The data from the CRPT in pumping well PW-BO were analysed using the AQTSolve
software and evaluated with the Theis and Jacob equations for confined aquifers.
Because the pumping for the pumping well took place in the well itself, the storage
coefficient obtained is not valid. An aquifer thickness of 57 m and total penetration of
the well in the aquifer were assumed (see Figure 1-8, Figure 1-9). The equations are
given in Figure 1-10 and Figure 1-11 and the AQTSolve curve fitting adjustment results
are summarized in Figure 1-12 and Figure 1-13.
Annex II Appendix B
355
8 Figure 1-8. Stratigraphy and completion of well PW-BO. 356
Annex II Appendix B
9
Figure 1-9. Stratigraphy and completion of well CW-BO.
Annex II Appendix B
357
10 Formulation: 𝑠𝑠=𝑄𝑄4∙𝜋𝜋∙𝑇𝑇∙𝜔𝜔(𝜇𝜇) 𝜇𝜇=𝑟𝑟2∙𝑆𝑆4∙𝑇𝑇∙𝑡𝑡 Where, Q= Pumping rate (L3/T) r= Radial distance from pumping well to observation well (L) s= Drawdown (L) S= Storage coefficient (dimensionless) t= elapsed time since start of pumping (T) T= Transmissivity (L2/T) W(u) = Well function (dimensionless) Figure 1-10. Theis’ (1935) Formula. Source: FCIHS, 2009 and Villanueva, 1984. 358
Annex II Appendix B
11
Formulation:
𝑇𝑇 = 0.183 ∙
𝑄𝑄
𝑚𝑚
𝑆𝑆 =
2.25 ∙ 𝑇𝑇 ∙ 𝑡𝑡0
𝑟𝑟2
Where,
m= Difference in
drawdown over one
logarithmic cycle (1/L)
Q= Pumping rate (L3/T)
r= Radial distance from
pumping well to
observation well (L)
s= Drawdown (L)
S= Storage coefficient
(dimensionless)
T0= Value of t at the
intercept (T)
T= Transmissivity
(L2/T)
Figure 1-11. Cooper- Jacob's (1946) Formula.
Source: FCIHS (2009) and Villanueva (1984).
m
1
Annex II Appendix B
359
12 Figure 1-12. Results of the Theis analysis of well PW-BO. Source: Results of adjustments in AQTSolve. Figure 1-13. Results of the Cooper-Jacob analysis of well PW-BO. Source: Results after adjustments in AQTSolve. The data from the CRPT in observation well CW-BO were also analysed. The observation well was located approximately 11 m away from the main well. An aquifer thickness of 93 m and partial penetration of the wells in the aquifer were assumed, given the information taken from the stratigraphy and completion of the wells (see Figure 1-8, 1.10.100.1000.1.0E+415.15.315.615.916.216.516.817.117.417.718.Time (min)Displacement (m)Obs. WellsPW-BOAquifer ModelUnconfinedSolutionTheisParametersT = 450.2 m2/dayS = 2.416E-41Kz/Kr = 1.b = 57. m1.10.100.1000.1.0E+415.15.315.615.916.216.516.817.117.417.718.Time (min)Displacement (m)Obs. WellsPW-BOAquifer ModelUnconfinedSolutionTheisParametersT = 450.2 m2/dayS = 2.416E-41Kz/Kr = 1.b = 57. m 360
Annex II Appendix B
13
Figure 1-9). The data were analysed using equations from Theis (1935) and Cooper
Jacob (1946) for confined aquifers. The equations are given in Figure 1-10 and Figure
1-11, respectively. The results of the curve fitting adjustments made in AQTSolve are
given in Figure 1-14 and Figure 1-15.
Figure 1-14. Results of the Theis analysis of observation well CW-BO.
Source: Results of adjustments in AQTSolve.
1. 10. 100. 1000. 1.0E+4
0.
0.2
0.4
0.6
0.8
1.
Time (min)
Displacement (m)
Obs. Wells
CW-BO
Aquifer Model
Confined
Solution
Theis
Parameters
T = 1087.8 m2/day
S = 0.0001982
Kz/Kr = 5.865E+6
b = 93. m
Annex II Appendix B
361
14 Figure 1-15. Results of the Cooper-Jacob (1946) analysis of observation well CW-BO. Source: Results of adjustments in AQTSolve. The recovery was analysed using the Recovery Theis (1935) equation. The graphs and results derived from this analysis are summarized in Figure 1-16. An aquifer thickness of 93 m was used because it was assumed that the observation well provides a conduit for water from depth to the PW-BO well. The parameters obtained are given in Table 1-2. 1.10.100.1000.1.0E+40.0.20.40.60.81.Adjusted Time (min)Displacement (m)Obs. WellsCW-BOAquifer ModelConfinedSolutionCooper-JacobParametersT = 1087.8 m2/dayS = 0.0001982 362
Annex II Appendix B
15
Data:
M=0.11
Q=10.8 l/s (933.12
m3/d)
B= 100 m (assuming
influence of well CWBO)
Formula:
T= 0,178 ∗ 𝑄𝑄
𝑚𝑚
Results:
T= 1626 m2/d
K= 17 m/d
Data:
M=0.15
Q=10.8 l/s (933.12
m3/d)
B= 100 m
Results:
T= 1177 m2/d
K= 13 m/d
Figure 1-16. Analysis of recovery from the CRPT in the PW-BO and CW-BO wells.
M=0.11
M=0.15
Annex II Appendix B
363
16 Analyzed test Method T (m2/d) K (m/d) S Aquifer depth CRPT in well PW-BO Theis 450 8 -- 57 CRPT in well PW-BO Jacob 450 8 - 57 CRPT in well CW-BO Theis 1087 12 2∙10-4 93 CRPT in well CW-BO Jacob 1087 12 2∙10-4 93 Recovery well PW-BO Theis 1626 17 - 93 Recovery observation well CW-BO Theis 1177 13 - 93 Table 1-2. Summary of parameters obtained. 2 PW-UQN WELL 2.1 Pumping Tests A five-step Variable-Rate Pumping Test (VRPT) or step-drawdown test was performed in well PW-UQN. The pumping rates ranged from 10 to 30 l/s. The optimal pumping rate was estimated to be 20 l/s. After recovery, a CRPT was performed with a flow rate of 20 l/s, and recovery was measured. Pressure transducers were installed in well PW-UQN, and also in the observation well MWL-UQN. Water levels were also measured manually throughout the testing. 2.1.1 Variable-Rate Pumping Test (VRPT) in Well PW-UQN The five-step variable-rate pumping test was conducted on 24 November, 2016 with approximate pumping rates of 10, 15, 20, 25, and 30 l/s. Notably, in the first three steps, water levels stabilized. For the maximum pumping rate, the drawdown was 12.27 m, and recovery to 90% took place in 50 minutes after pumping stopped. Figure 2-1 plots the data obtained. When the test began, water levels had recovered from the pre-test pumping. The results of the variable-rate pumping test are plotted in Figure 2-1 and Figure 2-2. The results are consistent with the response expected for a confined aquifer. The observation well was located 13 m away from the pumping well and had a maximum drawdown of 8.44 m. See Figure 2-3. 364
Annex II Appendix B
17
Figure 2-1. Variable-rate pumping test in well PW-UQN.
Flow rate
l/s
Duration
(min)
Starting
level
(m.b.g.l..)
Ending
level
(m.b.g.l..)
Cumulative
drawdown
(m.b.g.l..)
Head
stabilization
10 160 9.43 11.95 2.52 No
15 210 11.95 13.83 4.4 Yes
20 540 13.83 16.58 7.15 Yes
25 390 16.58 18.64 9.21 Yes
30 180 16.59 21.7 12.27 No
Table 2-1. Summary of variable-rate pumping test (VRPT) in well PW-UQN.
Annex II Appendix B
365
18 Figure 2-2. Drawdowns during the VRPT in the PW-UQN well. 366
Annex II Appendix B
19
Figure 2-3 .Variable-rate pumping test in the MWL-UQN well.
2.1.2 Constant-Rate Pumping Test (CRPT) in Well PW-UQN
The CRPT commenced on 25 November 2016 at 5:30 p.m., with an initial static water
level of 9.86 m.b.g.l. and pumping rate of approximately 20 l/s. The test lasted for 24
hours (Figure 2-4). When the test began, the water levels were close (drawdown 0.43 m)
to pre-variable-rate pumping test levels.
After approximately 7.5 hours of pumping (450 min), the water level stabilized at
around 16.72 m depth, i.e. a drawdown of 6.86 m. Once the test was over, recovery was
measured for 390 minutes. The well recovered rapidly, reaching 90% of the pre-test
water level by 35 minutes. A maximum drawdown of 5.06 m was seen in the
observation well, after which it recovered to the water level before the test (see Figure
2-5).
Annex II Appendix B
367
20 Figure 2-4. Recording water levels during the CRPT in well PW-UQN. Figure 2-5. Recording water levels during the CRPT in observation well MWL-UQN. 368
Annex II Appendix B
21
2.1.3 Estimating Transmissivity and Storage Coefficient from the CRPT results
The two boreholes (PW-UQN and MWL-UQN) both penetrate to the Silala and Cabana
ignimbrites, so might be expected to give similar results from analysis (see Figure 2-7).
For PW-UQN the results were: transmissivity (T) = 200-500 m2/d, permeability (K) =
4-9 m/d, and storage coefficient (S) = 1*10-4. The analyses are shown below.
Figure 2-6. Location of wells PW-UQN and MWL-UQN.
Annex II Appendix B
369
22 Figure 2-7. Geological cross-section of the PW-UQN, MWS-UQN, and MWL-UQN wells. The software AQTSolve was used to analyse the results from both the pumping and the observation wells. The observation well MWL-UQN was located approximately 13 m away from the main well. An aquifer thickness of 57 m was assumed based on the stratigraphy (see Figure 2-8, Figure 2-9, and Figure 2-10). Total penetration of the wells in the aquifer was assumed, though this may not be the case. The data were analysed using equations from Theis (1935) and Cooper-Jacob (1946) for confined aquifers. The equations are summarized in Chapter 1.1.3. The results of the AQTSolve curve fitting adjustments are summarized in Figure 2-11 and Figure 2-12. 370
Annex II Appendix B
23
Figure 2-8. Stratigraphy and completion of well PW-UQN.
Annex II Appendix B
371
24 Figure 2-9. Stratigraphy and completion of well MWS-UQN. Figure 2-10. Stratigraphy and completion of well MWL-UQN. 372
Annex II Appendix B
25
Figure 2-11. Results of the Theis (1935) analysis of observation well MWL-UQN.
Source: Results of adjustments in AQTSolve.
1. 10. 100. 1000. 1.0E+4
0.
1.6
3.2
4.8
6.4
8.
Time (min)
Displacement (m)
Obs. Wells
MWL-UQN
Aquifer Model
Confined
Solution
Theis
Parameters
T = 241.2 m2/day
S = 0.0001123
Kz/Kr = 1.
b = 57. m
Annex II Appendix B
373
26 Figure 2-12. Results of the Cooper-Jacob (1946) analysis of observation well MWL-UQN. Source: Results of adjustments in AQTSolve. Recovery was analysed using the Recovery Theis (1935) equation. The graphs and results derived from this analysis are summarized in Figure 2-13. The parameters obtained from the various estimates are summarized in Table 2-2. 1.10.100.1000.1.0E+40.1.63.24.86.48.Adjusted Time (min)Displacement (m)Obs. WellsMWL-UQNAquifer ModelConfinedSolutionCooper-JacobParametersT = 246.5 m2/dayS = 0.0001096 374
Annex II Appendix B
27
Data:
M=0.11
Q=20 l/s (1728
m3/d)
B= 100 m
Formula:
T= 0,178 ∗ 𝑄𝑄
𝑚𝑚
Results:
T= 510 m2/d
K= 8.9 m/d
Data:
M=0.11
Q=20 l/s (1728
m3/d)
B= 100 m
Results:
T= 471 m2/d
K= 8.3 m/d
Figure 2-13. Analysis of recovery from the CRPT in the PW-UQN and MWL-UQN wells.
Analyzed test Method T
(m2/d) K (m/d) S Aquifer
thickness
CRPT in well MWL-UQN Theis 241 4 10-4 57
CRPT in well MWL-UQN Cooper-
Jacob
247 4 10-4 57
Recovery well PW-UQN Theis 510 9 - 57
Recovery observation well
MWL-UQN
Theis 471 8 - 57
Table 2-2. Summary of parameters obtained.
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1 10 100 1000
Drawdown (m)
t/t'
Drawdown versus t/t' CRPT PW-UQN well
M=0.62
M=0.67
Annex II Appendix B
375
28 3 PW-DQN WELL 3.1 Pumping Tests A four-Step Variable-Rate Pumping Test (VRPT) or step-drawdown test was performed with pumping rates between 15 and 30 l/s. The optimal pumping flow rate was estimated to be 20 l/s. After recovery, a CRPT was carried out with a pumping rate of 20 l/s, and recovery was measured. Pressure transducers were installed in well PW-DQN, and also in the observation well MW-DQN. Water levels were also measured manually throughout the testing. 3.1.1 Variable-Rate Pumping Test (VRPT) in Well PW-DQN The four-step variable-rate pumping test was conducted on 7 December 2016 with approximate pumping rates of 15, 20, 25, and 30 l/s. Notably, the water level did not stabilize in any of the steps. For the maximum pumping rate, the drawdown was 10.27 m, and recovery to 90% took place in 390 minutes after pumping stopped. Figure 3-1 shows plots of the data obtained. Water levels had recovered from the pre-test pumping when the test began. The results are summarized in Table 3-1 and in Figure 3-2. The results are consistent with the response of a confined aquifer. The observation well was located 11 m away from the pumping well and the maximum drawdown was 9.63 m. See Figure 3-3. 376
Annex II Appendix B
29
Figure 3-1. Variable-rate pumping test in well PW-DQN.
Flow rate
l/s
Duration
(min)
Starting
level
(m.b.g.l..)
Ending
level
(m.b.g.l..)
Cumulative
drawdown
(m.b.g.l..)
Head
stabilization
15 180 3.64 7.54 3.9 No
20 140 7.54 8.8 5.16 No
25 210 8.8 11.95 8.31 No
30 270 11.95 13.91 10.27 No
Table 3-1. Summary of variable-rate pumping test (VRPT) in well PW-DQN.
Annex II Appendix B
377
30 Figure 3-2. Drawdowns during the VRPT in well PW-DQN. 02468101205101520253035Drawdown (
m)flow (l/s)Pumping rate versus drawdown PW-DQN well 378
Annex II Appendix B
31
Figure 3-3. Variable-rate pumping test in well MW-DQN.
3.1.2 Constant-Rate Pumping Test (CRPT) in PW-DQN Well
The CRPT commenced on 8 December 2016 at 9:30 a.m. with an initial static water
level of 5.81 m.b.g.l. and pumping rate of approximately 20 l/s. The test lasted for 24
hours (Figure 3-4). When the test began, water levels had not recovered from the
variable-rate pumping test. The difference in depth was approximately 2 m.
After about 24 hours (1140 min) of pumping, the water level appeared to be stabilizing
at a depth of 12.61 m, i.e. a drawdown of 6.8 m. Once the test ended, recovery was
measured for 160 minutes. The well recovered more slowly than wells PW-BO and PWUQN,
having only reached around 60% recovery after 160 minutes. The observation
well had a maximum drawdown of 6.89 m, after which it showed a similar rate of
recovery to the pumping well (see Figure 3-5).
Annex II Appendix B
379
32 Figure 3-4. Recording water levels during the CRPT in well PW-DQN. 380
Annex II Appendix B
33
Figure 3-5. Recording water levels during the CRPT in observation well MW-DQN.
3.1.3 Estimating Transmissivity and Storage Coefficient from the CRPT results
The data from the CRPT performed in pumping well PW-DQN and observation well
MW-DQN and their respective recovery results were analysed with AQTSolve
software. The location of the wells is shown in Figure 3-6. For well PW-DQN results of
analysis were: transmissivity (T) = 100-130 m2/d, permeability (K) = 2-4 m/d, and
storage coefficient (S) = 1*10-3. The analyses are shown below.
Annex II Appendix B
381
34 Figure 3-6. Location of wells PW-DQN and MW-DQN. The observation well MW-DQN was located approximately 11 m from the main well (see Figure 3-6). Both wells were completed in the Silala Ignimbrite (see Figure 3-7). An aquifer thickness of 36 m was assumed, obtained from the completions of wells PW-DQN and MW-DQN. Total penetration of the wells in the aquifer was also assumed (see Figure 3-8 and Figure 3-9). The data was analysed using equations from Theis (1935) and Cooper-Jacob (1946) for confined aquifers. The equations are summarized in Chapter 1.1.3. The results of the AQTSolve curve fitting adjustments are summarized in Figure 3-10 and Figure 3-11. 382
Annex II Appendix B
35
Figure 3-7. Geological cross-section of the PW-DQN and MW-DQN wells.
Figure 3-8. Stratigraphy and completion of well MW-DQN.
Annex II Appendix B
383
36 Figure 3-9. Stratigraphy and completion of well PW-DQN. 384
Annex II Appendix B
37
Figure 3-10. Results of the Theis (1935) analysis of observation well MW-DQN.
Source: Results of adjustments in AQTSolve.
1. 10. 100. 1000. 1.0E+4
0.
1.4
2.8
4.2
5.6
7.
Time (min)
Displacement (m)
Obs. Wells
MW-DQN
Aquifer Model
Confined
Solution
Theis
Parameters
T = 129.7 m2/day
S = 0.003477
Kz/Kr = 1.
b = 36. m
Annex II Appendix B
385
38 Figure 3-11. Results of the Cooper-Jacob (1946) analysis of observation well MW-DQN. Source: Results of adjustments in AQTSolve. Recovery was analysed using the Recovery Theis (1935) equation. The graphs and results derived from this analysis are summarized in Figure 3-12. The advantage of this analysis is that it does not require large amounts of data to be performed and is therefore applicable to both unconfined and confined aquifers. The parameters obtained from the various estimates are summarized in Table 3-2. 1.10.100.1000.1.0E+40.1.42.84.25.67.Adjusted Time (min)Displacement (m)Obs. WellsMW-DQNAquifer ModelConfinedSolutionCooper-JacobParametersT = 129.7 m2/dayS = 0.003477 386
Annex II Appendix B
39
Data:
M=0.11
Q=20 l/s (1728 m3/d)
B= 100 m
Formula:
T= 0,178 ∗ 𝑄𝑄
𝑚𝑚
Results:
T= 107 m2/d
K= 3.0 m/d
Data:
M=0.11
Q=20 l/s (1728 m3/d)
B= 60 m
Results:
T= 102m2/d
K= 2.8 m/d
Figure 3-12. Analysis of recovery from the CRPT in the PW-UQN and S2B wells.
Analyzed test Method T (m2/d) K (m/d) S Aquifer
thickness
CRPT in well MWDQN
Theis 130 3.6 3∙10-3 36
CRPT in well MWDQN
Cooper-
Jacob
130 3.6 3∙10-3 36
Recovery well PWDQN
Theis 107 3.0 - 36
Recovery observation
well MW-DQN
Theis 102 2.8 - 36
Table 3-2. Summary of parameters obtained.
M=2.95
M=3.1
Annex II Appendix B
387
40 4 CONCLUSION The transmissivity varies considerably beneath the Silala River ravine. It would appear that this heterogeneity occurs both in the horizontal and vertical directions. The total range of transmissivity was 100-1600 m2/d and permeability is in the range of 3-17 m/d. Storativity values varied between 10-4 and 10-3, these are typical values for a confined aquifer. Well Transmissivity (T) (m2/d) Permeability (K) (m/d) Storage Coefficient (S) PW-BO 450-1600 8-17 2*10-4 PW-UQN 200-500 4-9 1*10-4 PW-DQN 100-130 3-4 1*10-3 5 REFERENCES Bentall, R., 1963. Methods of determining permeability, transmissibility and drawdown. Geological Survey Water-Supply Paper, 1536-I, 243-341. Cooper, H.H. Jr., Jacob, C.E., 1946. A generalized graphical method for evaluating formation constants and summarizing well field history, Trans. Amer. Geophys. Union, 27(4), 526-534. Cooper, H.H. Jr., Jacob, C.E., 1953. A generalized graphical method for evaluating formation constants and summarizing well-field history. U.S. Department of the Interior Geological Survey, Ground Water Notes Hydraulics, N°7, 90-102. FCIHS.2009. Hidrogeología. Comisión Docente Curso Internacional de Hidrología Subterránea. Barcelona, España. Jacob, C.E., 1940. On the flow of water in an elastic artesian aquifer. Trans. Amer. Geophys. Union, 21(2), 574-586. Jacob, C.E., 1941. Coefficients of storage and transmissibility obtained from pumping tests in the Houston District, Texas. Trans. Amer. Geophys. Union, 22(3), 744-756. SERNAGEOMIN, 2017. Geology of the Silala River Basin. (Vol. 5, Appendix VIII). Theis, C.V., 1935. The relation between the lowering of the Piezometric surface and the rate and duration of discharge of a well using groundwater storage. Trans Amer. Geophys. Union 16(2), 519-524. 388
Annex II Appendix B
41
Tseng, P.-H., Lee, T.-Ch., 1997. Numerical evaluation of exponential integral: Theis
well function approximation. Journal of Hydrology, 205(1-2), 38-51.
Villanueva, Manuel. 1984. Pozos y Acuífero: Técnicas de Evaluación Mediante
Ensayos de Bombeo. Instituto Geológico y Minero de España. Madrid, España. 426pp.
Annex II Appendix B
389
390
Annex II
Annex II Appendix C
391
1
APPENDIX C
GEOPHYSICS
1 INTRODUCTION
As part of the hydrogeological study, and to complement the geological information
obtained from the drilling investigations in the study area, two geophysical studies were
conducted (Figure 1-1).
1. Multiparameter well logging, measuring natural gamma, porosity, near and far
resistivity (Geodatos, 2017).
2. An Electrical Resistivity Tomography (ERT survey), calibrated using isolated
NanoTEM (nano-transient electromagnetic, Geodatos, 2016) measurements.
Both the ERT and NanoTEM methods are used to identify geological units in the
subsurface based on their different resistivities, which in this case correlated with wetter
and drier zones and varying clay content. The natural gamma and porosity
measurements were used to identify lithological changes in the wells logged.
Dual neutron and dual induction logging probes were used to measure natural gamma
and porosity and near and far resistivity, respectively. The natural gamma method
measures the total gamma radiation emitted from a formation. The intensity of the
natural gamma is an intrinsic property of a rock usually related to clay content. Porosity,
on the other hand, exists in an indirect relationship to the variable measured, because the
test measures the number of hydrogen (in water filled porosity) atoms in a formation;
the more hydrogen atoms, the higher the porosity of a deposit or rock formation.
The ERT and NanoTEM methods involved placing electric dipoles linearly along the
surface every 5 or 6 m (and multiples of this distance) in order to reach investigation
depths of between 50 and 60 m. The greater the distance between the dipoles, the deeper
the investigation can go but at a lower resolution. In this study, the dipole placement
provided good data resolution in the first 50-60 m of the subsurface. TEM is an
inductive electromagnetic method that runs in the time domain. Using metal loops
installed in the ground, conduction currents are generated in the subsoil and the transient
magnetic field produced by the decay of these currents when transmission stops is
measured (Geodatos, 2017).
The company Geodatos collected this geophysical information for the survey in
December 2016 and March 2017.
392
Annex II Appendix C
2 Figure 1-1. Location map of geophysical studies.
Annex II Appendix C
393
3
2 WELL LOGGING RESULTS
Logging was carried out in six wells: PW-BO, PW-UQN, EW-PS, PW-DQN, MWLUQN
and MW-DQN (Figure 1-1). The former two (PW-BO, PW-UQN and MWLUQN)
display similar characteristics. Wells PW-BO and PW-UQN are 80m deep
whereas well MWL-UQN is 60 m deep. The logging conducted is shown below with
the geological units found in each well in Figure 2-1, Figure 2-2, and Figure 2-3. These
descriptions show that significant shifts in natural gamma are consistent with the
lithological changes noted from drill cuttings at some 45 m.b.g.l. in wells PW-UQN and
MWL-UQN (Figure 2-2 and Figure 2-3 respectively) and at some 65 m.b.g.l. in well
PW-BO (Figure 2-1). The porosity logging returned various peaks within the ignimbrite
units, which would be related to zones of high water content and hence high porosity.
These areas may be more fractured or if similar deflections are seen in the gamma logs
they may indicate increased clay content (clay normally has a high unconnected
porosity).
The logging in wells EW-PS and PW-DQN does not display any significant breaks in
the values logged (Figure 2-4 and Figure 2-5), so there is no correlation with the
lithology in the two wells. However, in well EW-PS the natural gamma values were
above 100 API, which seems likely to be correlated with the presence of clay, the result
of weathering of the Cabana Ignimbrite.
The gamma-ray curve logged in well MW-DWN seems to respond to lithologic change,
with a marked increase in gamma-ray values at some 10 m.b.g.l., in the contact between
fluvial deposits and the Silala Ignimbrite (Figure 2-6). Porosity curve shows marked
peaks in the uppermost Silala Ignimbrite.
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4 Figure 2-1. Logging in Well PW-BO.
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395
5
Figure 2-2. Logging in Well PW-UQN.
396
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6 Figure 2-3. Logging in Well MWL-UQN.
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397
7
Figure 2-4. Logging in EW-PS.
398
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8 Figure 2-5. Logging in Well PW-DQN.
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9
Figure 2-6. Logging in Well MW-DQN.
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10 3 TOMOGRAPHY AND NANOTEM RESULTS Nine 2D resistivity cross-sections were generated from the survey results. Five of these are from whole sections (P1, P3, P5, P8, and P9), while the remaining four (P2, P4, P6, and P7) were divided into stretches of approximately 600 m, with an overlap of around 150 m between them. Sections P2 and P4 were divided into three profiles, section P6 into 7 profiles, and section P7 into 16 profiles. The latter section corresponds to the entire length of the Silala River within the study area. Figure 1-1 is a site map with the location of all of the cross-sections, while Figure 3-1 to Figure 3-34 show each resistivity profile interpreted. The 34 resistivity profiles obtained have a scale of resistivity ranging between 20 and 1,000 Ohm-m. High resistivity values are associated with geological units that have low water saturation, little clay, and more resistive geological materials, like fresh rock. Low resistivity values are associated with water saturated highly fractured rock and/or a high clay content. Three broad geoelectrical units emerged from interpreting the profiles. These units are (see Figure 3-1): UGE-1 (low resistivity), UGE-2 (high resistivity), and UGE-3 (medium resistivity). UGE-1 This is a relatively low-resistivity unit, where most values were found to be around 100-200 Ohm – metres (Ohm-m), but the total range was between 20 and 250 Ohm-m. The unit has a variable thickness between 20 and 100 m, observable in most of the profiles, at depths of between 0 and 70 meters below ground level (m.b.g.l.). This unit is located mainly in the shallow depths under the base of the main ravines in the study area: Silala River (P7 - Figure 3-17 to Figure 3-32; P1 -Figure 3-2; P2.2 - Figure 3-4; P8 - Figure 3-33; and P5 - Figure 3-10), Quebrada Negra (P3 - Figure 3-6; and P9 - Figure 3-34), and Quebrada Inacaliri (P4.1 - Figure 3-7; and P6.1 - Figure 3-1). In some zones, especially under the ravines, the profiles show some vertical continuity from the base of the ravine with depth. These zones may be associated with areas that have fractures or faults but could also be areas where water recharges or discharges from springs or to the river in the Silala ravine. Beneath the Silala River, there are three areas where this geophysical unit is more than 70 m thick. The first is in the lower course of the Silala River near the Inacaliri Police Station at the confluence between the Silala River and the Quebrada Inacaliri, and extends for approximately 300 m (Profile P7.5, Figure 3-21); the second is in the DQN zone downstream of the confluence of the Silala River and the Quebrada Negra and about 250 m long (Profile 7.12, Figure 3-28).
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11
The third is in the BO zone and stretches for approximately 400 m (Profile P7.16,
Figure 3-32). Since there still appears to often be an upper and a lower low resistivity
layer the upper may be associated with saturated or partially saturated fluvial deposits
(see later UGE-3). The lower layer would appear to be correlated with saturated
Ignimbrites.
The wells PW-BO, PW-DQN, PW-UQN, and PW-UQI, drilled during this study, have
been included in profiles P1 (Figure 3-2), P8 (Figure 3-33), P2.2 (Figure 3-4), and P4.1
(Figure 3-7). These profiles show that the low-resistivity zone toward the base of the
profiles is correlated with the Cabana Ignimbrite and Silala Ignimbrite geological units.
UGE-2
A high-resistivity geological unit with values ranging between 250 and 1000 Ohm-m,
with an estimated thickness of 20 to 120 m, observed at depths of 0 to 60 m.b.g.l. These
high resistivity values could be associated with unsaturated and/or fresh rock, with little
fracturing and low amounts of clay. Profiles P1 (Figure 3-2), P8 (Figure 3-33), P2.2
(Figure 3-4), and P4.1 (Figure 3-7), could be associated with the unsaturated zones of
the alluvial deposits, fluvial deposits, as well as the unsaturated ignimbrites and other
volcanic rocks.
This unit is mainly located far away from the main riverbeds and ravines in the area of
study, as can be seen in profiles P2.1 and P6.3, P6.4, and P6.5 (Figure 3-3, Figure 3-12,
Figure 3-13, and Figure 3-14 respectively). However, in the lower Silala area, there are
two places where this unit is found directly underlying the Silala River: first, in the area
downstream of the Inacaliri Police Station, seen in profile P7.1 (Figure 3-17), and then
500 m upstream of the confluence of the Quebrada Inacaliri and the Silala River,
represented in profiles P4.3, P7.7, P7.8, and P7.9 (Figure 3-9, Figure 3-23, Figure 3-24,
and Figure 3-25, respectively). In these zones, it can be inferred that there is practically
no interaction between the Silala River surface water and the geological units
underlying them.
UGE-3
This is the geoelectrical unit closest to the surface. Its resistivity values range between
150 and 400 Ohm-m, and thickness ranges between 5 and 20 m. Its shape is tabular and
is located just a few meters under the ground surface. This “unit” may be associated
with saturated zones or zones with higher amounts of clay of the alluvial or fluvial
deposits.
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12 They exist throughout practically the entire study zone. Under the Silala River, this unit is correlated with fluvial deposits and is less thick than in zones outside of the valley, as can be seen in profile P7 (Figure 3-17 to Figure 3-32). Outside the Silala River ravine, this unit is relatively thicker and is correlated with perched groundwater in the alluvial deposits. The presence of this unit underlying the Silala River suggests that this unit's surface waters interact with the groundwater that could be in this unit, i.e. it is a zone of water recharge or discharge for the river. Moreover, there are zones where this unit directly overlies the UGE-1, which could indicate areas where there is fracturing and/or groundwater saturation, which would allow for deep flows to rise up or would allow infiltration of groundwater into deeper regions.
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13
Figure 3-1. ERT Profile P6.1.1
1 This and the following figures can be found in pdf format in the Data CD, Geodatos Folder.
404
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14 Figure 3-2. ERT Profile P1.
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405
15
Figure 3-3. ERT Profile P2.1.
406
Annex II Appendix C
16 Figure 3-4. ERT Profile P2.2.
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407
17
Figure 3-5. ERT Profile P2.3.
408
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18 Figure 3-6. ERT Profile P3.
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409
19
Figure 3-7. ERT Profile P4.1.
410
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20 Figure 3-8. ERT Profile P4.2.
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21
Figure 3-9. ERT Profile P4.3.
412
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22 Figure 3-10. ERT Profile P5.
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23
Figure 3-11. ERT Profile P6.2.
414
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24 Figure 3-12. ERT Profile P6.3.
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25
Figure 3-13. ERT Profile P6.4.
416
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26 Figure 3-14. ERT Profile P6.5.
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27
Figure 3-15. ERT Profile P6.6.
418
Annex II Appendix C
28 Figure 3-16. ERT Profile P6.7.
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419
29
Figure 3-17. ERT Profile P7.1.
420
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30 Figure 3-18. ERT Profile P7.2.
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31
Figure 3-19. ERT Profile P7.3.
422
Annex II Appendix C
32 Figure 3-20. ERT Profile P7.4.
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423
33
Figure 3-21. ERT Profile P7.5.
424
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34 Figure 3-22. ERT Profile P7.6.
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425
35
Figure 3-23. ERT Profile P7.7.
426
Annex II Appendix C
36 Figure 3-24. ERT Profile P7.8.
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427
37
Figure 3-25. ERT Profile P7.9.
428
Annex II Appendix C
38 Figure 3-26. ERT Profile P7.10.
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39
Figure 3-27. ERT Profile P7.11.
430
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40 Figure 3-28. ERT Profile P7.12.
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41
Figure 3-29. ERT Profile P7.13.
432
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42 Figure 3-30. ERT Profile P7.14.
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433
43
Figure 3-31. ERT Profile P7.15.
434
Annex II Appendix C
44 Figure 3-32. ERT Profile P7.16.
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435
45
Figure 3-33. ERT Profile P8.
436
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46 Figure 3-34. ERT Profile P9.
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437
47
4 REFERENCES
Geodatos, 2017. Geophysical Study: Geophysical Borehole Logging. Silala River Basin
Project, Región de Antofagasta, Chile. (Data CD, Geodatos Folder).
Geodatos, 2016. Geophysical Study: Electric Resistivity Tomography - NanoTEM.
Silala River Basin Project, Región de Antofagasta, Chile. (Data CD, Geodatos
Folder).
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1
APPENDIX D
HIGH-RESOLUTION TOPOGRAPHY
1 Methodology
Between November 2016 and January 2017, a high-resolution survey was conducted
using a photogrammetric flight with a Remotely Piloted Aircraft System and postprocessing
and collection of coordinates with differential GPS. The results are
summarized below.
1.1 High-Resolution Topographical Survey
A high-resolution digital elevation model was required to use as the basis for the
hydrogeological conceptual model. A photogrammetric flight with a Remotely Piloted
Aircraft (Drone) System (RPAS) was carried out.
The drone used was a DJI, model Phantom 3 Professional, with Pix4D Capture flight
control software, used to design the flight lines, which in this case mainly involved 500
m x 500 m scenes with an overlap of 70% between images and a flight height of 120 m.
A Ground Control Point (GCP) was set up at each of the drone take-off points, which
were measured on the ground with a differential GPS, obtaining precision of the order
of 10 cm.
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2 Figure 1-1. Flight plan for the photogrammetric survey using RPAS. The survey produced a set of 5055 photograms and 15 Ground Control Points. Once the information was downloaded, the data underwent post-processing to generate a point cloud (a set of data points in some coordinate system) and the digital elevation model.
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3
Figure 1-2. Handling the drone for take-off and landing.
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4 Name UTM East (m) UTM North (m) Elevation A 599067.411 7565577.210 4349.935 B 599864.678 7564933.898 4292.605 D 597991.952 7565414.769 4308.948 E 598981.580 7564897.548 4285.592 F 599961.130 7564390.619 4292.849 G 596983.983 7564896.505 4185.699 H 597992.313 7564397.741 4208.497 I 598943.737 7563918.267 4213.896 J2 599467.441 7563881.027 4236.832 K 595987.639 7564909.808 4167.668 L2 596973.244 7564069.280 4119.580 M 597986.560 7563392.326 4204.809 P 595977.037 7563899.147 4073.224 T 595964.496 7562867.254 4010.691 W2 595493.016 7562386.525 3975.694 Table 1-1. Ground Control Points – UTM WGS84 19S Coordinates. 1.2 Post-Processing of the Information Gathered by the Drones The Pix4d program was used to post-process the information gathered by the drone. This program takes the photographs from the flight and georeferences them using the GPS data, thus developing a preliminary raster grid (DTM) that offers an idea of what the final result will look like. Once the images have been processed and georeferenced, and the grid has been generated, the next step is to rectify the positioning with the aid of the ground support. This was conducted in parallel to the aerial photogrammetric survey. This support involved taking strategically-distributed reference points that were also captured by the drone camera. With these coordinates, the next step is to locate the photographs where
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5
the Control Points appear and, using the program, specifically, the Raycloud (point
cloud) module, correct the coordinates at each checkpoint based on the field results.
Once these data have been entered, we proceeded to reprocess the images and develop
the final raster using the digital terrain model (DTM), point cloud, contour lines, and the
orthomosaics with centimetre-level precision.
This final result produces detailed terrain-level data that can be run through various
programs depending on what is needed. Several of these formats include DWG, DXF,
or GIS. Photos 1 to 4 show the details of the steps performed.
Photo 1. Example of the first process, where the program takes photographs and positions them
on the basis of the data collected.
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6 Photo 2. Generating a raster with the digital terrain model.
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445
7
Photo 3. Results of correcting the positioning and generating the point cloud.
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8 Photo 4. Obtaining the contour lines from the raster that can be exported in dxf format. 1.3 Well Summaries On January 4 and 5, the coordinates of the wells located in the Silala River sector were surveyed using a Dual Frequency GPS System with Post-Processing, Brand ASTECH, Model Promark 100, which included a base station and a mobile station. In terms of the methodology, the work involved establishing Control Points to perform the survey. The points used were the Flamengo Mine Measurement Milestone Checkpoint (HMFL, in Spanish) and the Inacaliri Checkpoint (INAC, in Spanish). After collecting each coordinate for the wells, using the Stop & Go survey system, the information was downloaded and underwent post-processing, which produced the definitive coordinates for each of the wells surveyed with a very high level of precision, because the dual frequency GPS system was used. Below are the summaries of the wells surveyed in the field on January 4 and 5.
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447
9
Well name MW-BO
Location Boundary sector
Coordinate East (WGS84 19S) Coordinate North (WGS84 19S) Elevation (EGM
2008)
600,191.619 7,565,286.960 4,273.086
Figure 1-3. Summary of well MW-BO.
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10 Well name PW-BO Location Boundary sector Coordinate East (WGS84 19S) Coordinate North (WGS84 19S) Elevation (EGM 2008) 600,185.090 7,565,278.322 4,272.621 Figure 1-4. Summary of well PW-BO.
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11
Well name CW-BO
Location Boundary sector
Coordinate East (WGS84 19S) Coordinate North (WGS84 19S) Elevation (EGM
2008)
600,174.705 7,565,266.583 4,272.604
Figure 1-5. Summary of well CW-BO.
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12 Well name MWL-UQN Location Upstream Quebrada Negra sector Coordinate East (WGS84 19S) Coordinate North (WGS84 19S) Elevation (EGM 2008) 599,352.862 7,564,072.179 4,205.129 Figure 1-6. Summary of well MWL-UQN.
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13
Well name PW-UQN
Location Upstream Quebrada Negra sector
Coordinate East (WGS84 19S) Coordinate North (WGS84 19S) Elevation (EGM
2008)
599,346.414 7,564,063.247 4,204.590
Figure 1-7. Summary of well PW-UQN.
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14 Well name MW-UQN Location Upstream Quebrada Negra sector Coordinate East (WGS84 19S) Coordinate North (WGS84 19S) Elevation (EGM 2008) 599,346.414 7,564,063.247 4,204.590 Figure 1-8. Summary of well MW-UQN.
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15
Well name SPW-DQN
Location Downstream Quebrada Negra sector
Coordinate East (WGS84 19S) Coordinate North (WGS84 19S) Elevation (EGM
2008)
599,091.110 7,563,870.565 4,189.800
Figure 1-9. Summary of well SPW-DQN.
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16 Well name PW-DQN Location Downstream Quebrada Negra sector Coordinate East (WGS84 19S) Coordinate North (WGS84 19S) Elevation (EGM 2008) 598,838.646 7,563,779.894 4,178.465 Figure 1-10. Summary of well PW-DQN.
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17
Well name MWL-DQN
Location Downstream Quebrada Negra sector
Coordinate East (WGS84 19S) Coordinate North (WGS84 19S) Elevation (EGM
2008)
598841.323 7,563,769.179 4,179.384
Figure 1-11. Summary of well MWL-DQN.
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18 Well name EW-PS Location Inacaliri Police Station sector Coordinate East (WGS84 19S) Coordinate North (WGS84 19S) Elevation (EGM 2008) 596,388.241 7,563,832.860 4,032.157 Figure 1-12. Summary of well EW-PS.
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19
Well name PW-UQI
Location Upstream Quebrada Inacaliri sector
Coordinate East (WGS84 19S) Coordinate North (WGS84 19S) Elevation (EGM
2008)
596,388.241 7,563,832.860 4,032.157
Figure 1-13. Summary of well PW-UQI.
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20 Checkpoint Name Inacaliri (INAC) Location Inacaliri Police Station and Cell-phone Tower sector Coordinate East (WGS84 19S) Coordinate North (WGS84 19S) Elevation (m.a.s.l.) 596,314.553 7,563,923.064 4,084.600 Figure 1-14. Inacaliri Checkpoint INAC.
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21
Checkpoint Name Flamengo Mine Measurement Milestone (HMFL)
Location Sector going down to Silala ravine
Coordinate East (WGS84 19S) Coordinate North (WGS84 19S) Elevation (m.a.s.l.)
598,464.466 7,564,264.108 4,222.200
Figure 1-15. Flamengo Mine Measurement Milestone Checkpoint HMFL.
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1
APPENDIX E
INFILTRATION TESTS
1 INTRODUCTION
This document presents the results of infiltration tests performed as part of the
fieldwork that Arcadis carried out on 17 and 22 December 2016, for the detailed
hydrogeological study of the Silala River.
The test sites were chosen to enable characterization of the permeability of a selection
of the surface geological deposits in the Silala catchment. The Guelph permeameter and
double ring methods were used.
2 METHODOLOGY
2.1 Guelph Permeameter
This permeameter consists of two concentric tubes with different-sized diameters. One
acts as a water container and the other smaller tube is placed in contact with the soil and
is coupled to a system to maintain a constant hydraulic head (see Figure 2-1).
Measuring hydraulic conductivity using the permeameter involves measuring the speed
at which the water level in a cylinder changes as the water infiltrates into the soil. The
Guelph permeameter is a constant-head permeameter that relies on the Mariotte
principle (McCarthy, 1934). This method makes it possible to measure the rate of water
recharge in a steady state in unsaturated soil (in a borehole), where the water head is
maintained at a constant level. For further theoretical discussion regarding the use and
applicability of the Guelph Permeameter, it is recommended to consult Elrick et al.
(1989) and Zhang et al. (1998).
The first step is to bore a hole, preferably no deeper than 38 cm. In most soils, the
drilling process will lead to the formation of a layer at the edges that makes the soil
impermeable and affects the measurement. A brush is therefore used to remove any low
permeability layer.
The permeameter is then filled, which requires removing the top from the container and
ensuring that the flow-regulating valve's indicator is pointing upward to keep the inner
and outer reservoirs connected.
To install the equipment in the test hole, the permeameter is gently lowered through the
tripod whilst making sure that the support tube does not hide the sides of the hole.
If the borehole is more than 38 cm deep, the permeameter can be positioned without the
tripod using a support that slides over the ground to ensure that the equipment is stable.
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2 Before starting to collect data, it is necessary to check the set-up of the permeameter, confirming that the indicator at the valve at the base of the container is pointing upwards, the water level indicator is at the base of the top of the permeameter, and the hole to fill the closed permeameter and the vacuum tube are correctly sealed. Once the set-up of the permeameter has been checked, the height of the water level in the hole is determined using the height indicator on the upper part of the permeameter. If the rate of fall is very slow, the inner reservoir is selected by flipping the indicator downwards. Once the reservoir has been chosen, it can no longer be changed during the test. Figure 2-1. Description of the Guelph permeameter. Source: Operating instructions 2800K1(www.soilmoisture.com).
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3
Once the reservoir and the head to use have been selected, with the head ranging
between 5 and 10 cm in the tests carried out, 2 minutes should be allowed to achieve
soil saturation, before starting the test. After this time, data collection can begin. The
test is over when the rate of fall does not change significantly in three time intervals in a
row, indicating that the infiltration has reached a steady state. The data are recorded
every 1 or 0.5 minute, and the test would normally last between 2 and 15 minutes,
depending on the soil type.
The permeability values are calculated from the field measurements and the spreadsheet
in Figure 2-2. If there are two valid measurements at the same point with a different
head, the spreadsheet calculates the permeability with both and then calculates a
quadratic mean, which is the final value given. If there is only one valid measurement,
the value in the table will be the value calculated at that point.
Figure 2-2. Example of permeability spreadsheet.
HOJA DE REGISTRO PERMEAMETRO DE GUELPH
CALCULO DE CONDUCTIVIDAD HIDRAULICA CON 1 CARGA
Ensayo : LC-001
Fecha : 13.08.09 Coordenadas N: E:
Profesional : Mario Gajardo / Alvaro Elgueta Peso Específico de Sólidos Gs: 2,7
Humedad Inicial in Situ w : 15 %
Densidad Seca In Situ gd : 1,700 t/m3
a* = 0,04 cm-1 Profundidad de la Perforación 47 cm
Primer set de lecturas: H1 = 5 cm Segundo set de lecturas: H2 = 10 cm
Nº de Lectura
Tiempo
Intervalo de
Tiempo (min)
Nivel de Agua en
Reservorio (cm)
Variación de
Nivel de Agua
(cm)
Tasa de
Variación de
Nivel de Agua
(cm/min)
Nº de Lectura
Tiempo
Intervalo de
Tiempo (min)
Nivel de Agua en
Reservorio (cm)
Variación de
Nivel de Agua
(cm)
Tasa de
Variación de
Nivel de Agua
(cm/min)
1 2,00 0,50 6,80 1,20 2,40 1 2,50 0,50 12,00 1,20 2,40
2 2,50 0,50 7,90 1,10 2,20 2 3,00 0,50 13,20 1,20 2,40
3 3,00 0,50 9,00 1,10 2,20 3 3,50 0,50 14,20 1,00 2,00
4 3,50 0,50 10,20 1,20 2,40 4 4,00 0,50 15,50 1,30 2,60
5 4,00 0,50 11,40 1,20 2,40 5 4,50 0,50 16,50 1,00 2,00
6 4,50 0,50 12,50 1,10 2,20 6 5,00 0,50 17,60 1,10 2,20
7 5,00 0,50 13,50 1,00 2,00 7 5,50 0,50 18,60 1,00 2,00
8 5,50 0,50 14,60 1,10 2,20 8 6,00 0,50 19,80 1,20 2,40
9 6,00 0,50 15,90 1,30 2,60 9 6,50 0,50 20,90 1,10 2,20
10 6,50 0,50 16,90 1,00 2,00 10 7,00 0,50 21,90 1,00 2,00
11 7,00 0,50 17,90 1,00 2,00 11 7,50 0,50 23,00 1,10 2,20
12 7,50 0,50 18,90 1,00 2,00 12 8,00 0,50 24,00 1,00 2,00
2,00 2,00
R av Tasa de flujo en régimen permanente, obtenida cuando R es la misma al menos durante 3 intervalos de tiempo consecutivos
R1,av = 2,00 cm/min = 3,33E-02 cm/s R2,av = 2,00 cm/min = 3,33E-02 cm/s
Conductividad Hidraulica de Campo Kf s1 = 0,00087 x 35,22 x 3,33E-02 = 1,0E-03 cm/s
Kf s2 = 0,0006 x 35,22 x 3,33E-02 = 7,0E-04 cm/s Kf s, av = 8,5E-04 cm/s
Potencial de Flujo Matricial fm1 = 0,02179 x 35,22 x 3,33E-02 = 2,6E-02 cm/s
fm2 = 0,01511 x 35,22 x 3,33E-02 = 1,8E-02 cm/s fm, av = 2,1E-02 cm2/s
Parámetro Alfa (calculado) a = 8,48E-04 / 2,13E-02 a = 0,04 cm-1
Variación de Humedad Volumétrica Dq = 0,370 - 0,255 Dq = 0,115 cm3/cm3
Sortividad S = ( 2 x 0,11537 x 2,13E-02 ) 0.5 S = 7,0E-02 cm s-1/2
R1,av R2,av
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4 2.2 Double Ring Infiltrometer Tests This method involves saturating a portion of soil encircled by two concentric rings, measuring the amount of water infiltrating in the inner cylinder. The soil may be dry or partially wet, and therefore not saturated, when the test begins. In this case the initial infiltration may be high, and will start to decline until reaching steady state when the soil is saturated. The time needed to reach final saturation conditions will depend on the degree of wetness in advance, the texture and structure of the soil, the thickness of the area through which the water flows, and the height of the water in the inner ring. To perform the infiltration tests with the double-ring infiltrometer, the method described in the Standard Test Method for Infiltration Rate of Soils in Field Using Double-Ring Infiltrometer (ASTM, 2003) was used. The tests were performed on a flat surface. A trial pit of approximately 1.5 by 1.5 m with a depth of 15 to 30 cm was dug. The cylindrical metal rings (5 and 10 cm diameter) were placed on the surface of the trial pit, checking that there were no rocks or roots under the edge of any of them and that the inner cylinder was entirely centred inside the outer cylinder. Then the Mariotte tubes are placed, connected to the rings as shown in Figure 2-3. Before beginning the test, water is poured into the rings to saturate the soil as much as possible. Once the test begins, the rate of fall of the water level in the Mariotte tube over time is recorded. The test should last until the rate of fall of the water in the Mariotte tube reaches a steady state, as shown in the example in Figure 2-4. This rate is corrected depending on the area of the inner ring and the infiltrated volume.
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5
Figure 2-3. Set-up of infiltration tests with the double ring method.
Figure 2-4. Example of a figure showing the stabilization of the rate of fall.
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6 3 RESULTS This section presents the results of the permeability measurements conducted at the sites selected in the Silala catchment. Ten infiltration tests were conducted, 5 using the Guelph permeameter and 5 using the double ring. 3.1 Location of Measurement Sites The selection of test sites was designed to be representative of the characteristic soils and geology found in the Silala area. Table 3-1 summarizes the UTM coordinates of the points measured. Figure 3-1 shows the sites located on a map. Point Methodology UTM East (m) UTM North (m) Measurement date Characteristics of the terrain I1 Double ring 599,582 7,564,843 19-12-2016 Alluvial deposits, geological unit Pls(a) I2 Double ring 597,151 7,564,717 18-12-2016 Alluvial deposits, geological unit Pls(a) I3 Double ring 598,026 7,562,578 18-12-2016 Geological unit PlH(pc) I4 Guelph perm. 597,768 7,562,227 19-12-2016 Incipient soil south of the river, geological unit MsPvd I5 Guelph perm. 599,847 7,562,063 22-12-2016 Incipient soil south of the river, geological unit MsPvd I6 Guelph perm. 597,429 7,560,157 19-12-2016 Incipient soil south of the river, geological unit Piic I7 Double ring 600,123 7,565,216 18-12-2016 Fluvial deposits, geological unit Hf I8 Double ring 596,471 7,563,867 17-12-2016 Fluvial deposits, geological unit Hf I9 Guelph perm. 598,897 7,563,890 19-12-2016 Incipient soil north of the river, geological unit Pliis I10 Guelph perm. 601,503 7,560,285 19-12-2016 Incipient soil south of the river, geological unit Pliv(a) Table 3-1. Location of the points. Note: Coordinates in WGS84.
Annex II Appendix E
467
7
Figure 3-1. Location of measurement points.
3.2 Results of Permeability Measurements
Table 3-2 and Table 3-3 contain the results of the infiltration tests. The results of the 10
tests have geometric mean permeability of 0.32 m/day with a minimum value of 0.02
m/day and a maximum of 2.05 m/day.
The results from the Guelph permeameter tests are noteworthy, because 4 of the 5
measurement points returned permeabilities of over 0.3 m/day. Only site I5 had a lower
permeability (0.03 m/day). This low permeability is within the expected range for
incipient soils. On the other hand, the results using the double ring method reveal that
468
Annex II Appendix E
8 the fluvial and alluvial soils display high permeability, with values ranging between 0.19 and 2.05 m/day, which are within the expected range for this type of soil. Using the double ring method on the pyroclastic fall deposit pointed to a significantly lower permeability (0.02 m/day in I3), which is also to be expected, given how weathered this clay-rich unit is. To calculate the permeabilities with the Guelph permeameter, a spreadsheet was used with two calculation methods: the one-head and two-head methods. It is best to do calculations with the two-head method, but the results of that method are not always valid because negative values can be produced, in which case it is necessary to use the one-head method. According to the literature,1 highly heterogeneous soils can lead to negative permeability values which are invalid, because the theory used to calculate permeability assumes that the soil in the area surrounding the permeameter is homogeneous. One case where the soil being tested was highly heterogeneous is given in Figure 3-2, which shows a schematic view of a permeability test in heterogeneous soil, where an incipient soil layer (weathered rock) is covered by a soil layer of high horizontal permeability. In 4 of the 5 sites tested using the Guelph permeameter, the two-head calculation method led to invalid (negative) results, making it necessary to use the one-head method. These results are due to the presence of a thin layer of approximately 15 cm of fractured and weathered rock (incipient soil) located over rock (see an example in Figure 3-3). In such cases, the permeability calculated there is the combined permeability of the rock and the overlying incipient soil layer. Figure 3-2. Schematic view of a test in heterogeneous soil. 1 2800Ka Guelph Permeameter operation instructions, SOILMOISTUREEQUIPMENT CORP, July 2005.
Annex II Appendix E
469
9
Point
UTM
East
(m)
UTM
North (m)
Measurement
date
Depth
(cm) Reservoir Heads Permeability
(m/day)
I4 597,768 7,562,227 19-12-2016 25 Combined 2 1.61
I5 599,847 7,562,063 22-12-2016 30 Interior 1 0.03
I6 597,429 7,560,157 19-12-2016 25 Combined 1 0.48
I9 598,897 7,563,890 19-12-2016 25 Combined 1 0.37
I10 601,503 7,560,285 19-12-2016 25 Combined 1 0.93
Table 3-2. Results of the permeabilities measured with the Guelph permeameter.
Note: Coordinates in WGS84.
Point UTM East
(m)
UTM North
(m)
Measurement
date
Permeability
(m/day)
Expected
permeability
(m/day)
I1 599,582 7,564,843 19-12-2016 0.63 1 to 0.01
I2 597,151 7,564,717 18-12-2016 2.05 1 to 0.01
I3 598,026 7,562,578 18-12-2016 0.02 1 to 0.01
I7 600,123 7,565,216 18-12-2016 0.19 1 to 0.01
I8 596,471 7,563,867 17-12-2016 0.29 1 to 0.01
Table 3-3. Results of the double-ring permeability measurements.
Note: Coordinates in WGS84.
470
Annex II Appendix E
10 Figure 3-3. Incipient soil (Point I6). 4 REFERENCES ASTM Standard D3385-9, 2003. Standard Test Method for Infiltration Rate of Soils in Field Using Double-Ring Infiltrometer. ASTM International. Elrick, D.E., Reynolds, W.D. and Tan, K.A., 1989. Hydraulic conductivity measurements in the unsaturated zone using improved well analyses. Groundwater Monitoring & Remediation, 9(3), 184-193. McCarthy, E.L., 1934. Mariotte’s Bottle. Science, 80(2065), 100. SoilMoisture Equipment Corp., 2012. Guelph Permeameter 2800 Operating Instructions. Zhang, Z.F., Groenevelt, P.H., Parkin, G.W., 1998. The well shapefactor for the measurement of soil hydraulic properties using the Guelph Permeameter. Soil and Tillage Research, 49(3), 219-221.
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471
11
PHOTOS OF GUELPH PERMEAMETER MEASUREMENTS
Photo 1. Point I-4.
472
Annex II Appendix E
12 Photo 2. Point I-5.
Annex II Appendix E
473
13
Photo 3. Point I-6.
474
Annex II Appendix E
14 Photo 4. Point I-9.
Annex II Appendix E
475
15
Photo 5. Point I-10.
476
Annex II Appendix E
16 PHOTOS OF THE DOUBLE-RING TESTS Photo 6. Point I-1.
Annex II Appendix E
477
17
Photo 7. Point I-2.
478
Annex II Appendix E
18 Photo 8. Point I-3.
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479
19
Photo 9. Point I-7.
480
Annex II Appendix E
20 Photo 10. Point I-8.
Annex II Appendix F
481
1
APPENDIX F
BOREHOLE FLUID LOGGING
1. Methodology
In November and December 2016, an electrical conductivity and temperature logging
campaign was conducted in wells PW-BO, PW-UQN, CW-BO, and PW-DQN. The
Leveltroll200 instrument from In Situ, Inc. was used for this work. Below are the details
of the results obtained in each of the wells mentioned above.
1.1 PW-BO Well
The PW-BO well was completed with slotted screen starting at 24 m.b.g.l., so
groundwater flows will only be encountered below this depth. Above this, logs should
be ignored. Figure 1-1 shows that below 24 m, electrical conductivity is relatively
constant, rising slowly but sustainably with depth, ranging from 310 to 330 S/cm
approximately, with practically constant temperatures of 16.5 °C. These results suggest
that well PW-BO contains the same type of water over the entire screened region, with a
likely main intake of water located at the base of the well and an upward vertical flow.
This is consistent with what was observed when the well was being bored, where an
initial water inflow was observed at 24 m, increasing with depth, especially between 60
and 80 m.
482
Annex II Appendix F
2 Figure 1-1. Logging results in well PW-BO. 1.2 PW-UQN Well The PW-UQN well was completed with slotted screen beginning at 24 m.b.g.l., so the logging is only relevant below this depth. Figure 1-2 shows that below 24 m.b.g.l., electrical conductivity is relatively constant at about 305 S/cm but there was a change at 30-31 m.b.g.l. with a deviation indicating the entrance into the well of lower conductivity water. Below this level the conductivity is constant at about 320 S/cm. At 40 m.b.g.l. there was a deviation in the log to the right indicating entrance into the well of very slightly higher conductivity water. The temperature log revealed that the groundwater had a constant 19 °C temperature to 31 m.b.g.l. after which it rose to 19.2 °C at 34 m.b.g.l. Other minor deflections of the logs may indicate further inflows. During the drilling of the well, it was noted that there were two main inflow zones, located between 72 and 78 m and between 54 and 62 m.
Annex II Appendix F
483
3
Figure 1-2. Logging results in well PW-UQN.
1.3 CW-BO Well
CW-BO, the diamond cored well, was completed with slotted screen starting at 25.2
m.b.g.l., so the logging is only relevant below this depth. Figure 1-3 reveals that below
25 m.b.g.l., electrical conductivity had a relatively constant decline from about 300 to
260 S/cm with some deflections which may indicate water inflows or cross-flows. The
temperature log shows a variation between 16.8 and 17.8 °C. A constant temperature of
16.8 °C was observed down to 42 m.b.g.l. with a noticeable deflection and steadily
increasing temperature below this level. This suggests an inflow at about 42 m.b.g.l.
then upward flow to the base of the plain casing, and perhaps outflow at this point.
484
Annex II Appendix F
4 Figure 1-3. Logging results in well CW-BO. 1.4 PW-DQN Well The PW-DQN well was completed with slotted screen starting at 6 m.b.g.l., so the logging is only relevant below this depth. Figure 1-4 shows that below 6 m, electrical conductivity rises gradually with depth down to 31 m.b.g.l., from 160 to 220 S/cm. Below 31 m, electrical conductivity remains relatively constant, perhaps creeping up very slightly with depth. This may indicate a water inflow at the base of the well and an upward vertical flow. The temperature logging showed decreasing temperatures down to about 20 m.b.g.l. then a fairly constant temperature to the base of the well.
Annex II Appendix F
485
5
Figure 1-4. Logging results in well PW-DQN.
486
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Herrera, C. and Aravena, R., 2017. Chemical and Isotopic Characterization of Surface Water and Groundwater of
the Silala Transboundary Basin, Second Region, Chile
487
488
CHEMICAL AND ISOTOPIC CHARACTERIZATION OF SURFACE WATER
AND GROUNDWATER OF THE SILALA RIVER TRANSBOUNDARY BASIN,
SECOND REGION, CHILE
Christian Herrera (PhD)
Assistant Professor, Universidad Católica del Norte
Ramón Aravena (PhD)
Emeritus and Adjunct Professor, University of Waterloo
May, 2017
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489
GLOSSARY Alkalinity: The name given to the quantitative capacity of an aqueoussolution toneutralizeanacid. Anion:An ionic species, with a net negative charge. Aquifer: A permeable region of rock or soil capable of storing, transmitting and yielding exploitable quantities of water. Cation:Anionicspecies with a positive charge.Deuterium excess: The concept of deuterium excess (d) is defined as d=δ2H-8δ18O.The deuterium excess can be used to identify vapor source regions for air masses producing precipitation which contribute to groundwater recharge. Global meteoric line: An equation defined by the geochemist Harmon Craig that states the average relationship between hydrogen and oxygen isotope ratios in natural terrestrial waters, expressed as a worldwide average: δ2H = 8δ18O + 10‰.Headwater:A tributary stream of a river, close to or forming part of its source.Hydrochemical:Dealing with the chemical characteristics of bodies of water. Ion chromatography: A chromatography process that separates ions and polar molecules based on their affinity to an ion exchanger. Isotope: One or two or more species of the same chemical element, having the same numbers of protons in the nucleus but differing from one another by having a different numbers of neutrons. The isotopes of an element have slightly different physical properties, owing to their mass differences, by which they can be separated. Isotopic characterization:The identification of isotopic signature, the distribution of certain stable isotopes and radioactive isotopes within chemical compounds.Meteoric water line:Alinear equation that define the average relationship between hydrogen and oxygen isotope ratios in rain waters in an defined area. Mineralization: Process by which groundwater through interaction with minerals in the aquifer incorporated chemical elements in the water. Percent Modern Carbon: Unit to report radiocarbon dates. The reference is the radiocarbon content of the atmospheric CO2 before 1950 defined as 100 percent modern carbon. Perched aquifer:Groundwater body, generally of moderate dimensions, supported by a relatively impermeable stratum and which is located between a deeper water table and the ground surface. Plasma emission spectrometry: An analytical technique used for the detection of trace elements. It is a type of emission spectroscopy that uses the inductively coupled plasma 490
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to produce excited atoms and ions that emit electromagnetic radiation at wavelengths
characteristic of a particular element.
Radioactive isotope: A radioactive form of an element, consisting of atoms with
unstable nuclei, which undergo radioactive decay to stable forms, emitting characteristic
alpha, beta, or gamma radiation. These may occur naturally, as in the cases of tritium
and radiocarbon, or may be created artificially.
Recharge: Groundwater recharge (or deep drainage or deep percolation) is a
hydrologic process whereby water that has infiltrated the surface moves downward from
the unsaturated zone to groundwater. Recharge is the primary method through
which water enters an aquifer. Its source can be precipitation or surface water.
Redox process: A chemical reaction in which the oxidation states of atoms are
changed. Any such reaction involves both a reduction process and a complementary
oxidation process, two key concepts involved with electron transfer processes.
Salinity: The concentration of dissolved salts in water.
Silicate minerals: Silicate minerals are rock-forming minerals made up of silicate
groups. They are the largest and most important class of rock-forming minerals and
make up approximately 90 percent of the Earth's crust.
Silicate weathering: The destructive process by which silicate minerals on exposure to
atmospheric agents (water, wind, temperature changes, etc.) at or near the Earth's
surface are changed in color, texture, composition, firmness, or form, with little or no
transport of the loosened or altered material.
Silicate: A compound whose crystal structure contains SiO4 tetrahedral, either isolated
or joined through one or more the oxygen atoms to form groups, chains, sheets, or three
dimensional structures with metallic elements.
Stable isotope: One that does not transmute into another element with emission of
corpuscular or electromagnetic radiations.
Stagnant groundwater: Water present in low permeability rocks where the flow is
extremely low.
Tritium: A radioactive isotope of hydrogen. The nucleus of tritium contains
one proton and two neutrons. Naturally occurring tritium is rare on Earth, where trace
amounts are formed by the interaction of the atmosphere with cosmic rays.
Volumetric method: A quantitative chemical analysis that involves the measurement of
volume of a solution of known concentration which is used to determine the
concentration of the analyte.
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491
Weathering: The destructive process by which earth materials on exposure to atmospheric agents (water, wind, temperature etc.) at or near the Earth's surface are changed in color, texture, composition, firmness, or form, with little or no transport of the loosened or altered material. 492
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TABLE OF CONTENTS
1. INTRODUCTION ..................................................................................................... 1
1.1 Presentation ............................................................................................................. 1
1.2 Location of the investigated area............................................................................. 1
1.3 Objective of the report ............................................................................................. 2
1.4 Summary of the methodology ................................................................................. 2
1.5 Structure of the report.............................................................................................. 3
2. RESULTS AND DISCUSSION ................................................................................. 12
2.1 Geochemistry Data ................................................................................................ 12
2.2 Environmental isotope data ................................................................................... 14
2.2.1 δ18O and δ2H data ...........................................................................................15
2.2.2. Tritium Data...................................................................................................21
2.2.3 Carbon-14 and Carbon 13-Data......................................................................23
3. CONCLUSIONS ......................................................................................................... 26
4. REFERENCES............................................................................................................ 28
APPENDIX A ................................................................................................................. 30
APPENDIX B ................................................................................................................. 34
APPENDIX C ................................................................................................................. 38
APPENDIX D ................................................................................................................. 40
APPENDIX E ................................................................................................................. 48
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11.INTRODUCTION1.1 PresentationThe National Director of the Dirección Nacional de Fronteras y Límites del Estado (DIFROL) of the Ministry of Foreign Affairs of Chile, Mrs. Ximena Fuentes, requested a study concerning a hydrochemical and isotopic characterization of the transboundary basin of the Silala River in the Northern Chile region as part of a major study aimed atdeepening the hydrogeological knowledge of this basin. The study of the chemical and isotopic evolution of surface and groundwater in the Silala River basin can contribute to the understanding of the complex interaction between the river and the groundwater and mechanisms of local and regional recharge to the river flow. This report was elaborated under the supervision and instruction of Professors Howard Wheater and Denis Peach. 1.2 Location of the investigated areaThe headwaters of the Silala River are located above 4000 m.a.s.l.in Bolivian territorywhere the perennial river flow originates from two wetland areas, the Cajones and the Orientales, which are fed by groundwater from many springs. After the river enters a ravine it crosses into Chilean territory. In Chile, the basin is located between S-21.98°and S -22.06° latitude and W -68.08° and W-68.02° longitude, in the second region of Chile. The Silala Riverhas carved a ravine at the border between Chile and Bolivia, into the existing bedrock, that, in some places, is more than 10 m deep (Latorre and Frugone, 2017). Part of the flow of the river is diverted at a small impoundment just south west of the international border in Chilean territory. A major ephemeral tributary, called the Quebrada Negra (Figure 1), reaches the Silala River from the southeast, some 500 m downstream from the border (Latorre and Frugone, 2017). The upper course of the Silala River in this report refers to the area between the international border and Quebrada Negra, whereas the lower course term refers to the area between Quebrada Negra and the CODELCO intake (Figure 1), which is a surface water abstraction intake structure located downstream of the Silala River. 494
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2
Figure 1. Location map of the study area.
1.3 Objective of the report
The main objective of this study is to characterize the chemistry and isotopic
composition of the surface and groundwater of the Silala River basin. Chemical and
isotopic tracers can potentially provide information to evaluate the mechanisms of rivergroundwater
interaction and the origins of waters in the Silala River basin.
1.4 Summary of the methodology
Three periods of field work were conducted during the study. The first was carried out
during the 28th of August, 2017, by a multidisciplinary team. The main activities carried
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495
3 out during this field trip focused on evaluating the hydrogeological context of the study area and an evaluation of spring systems was also performed. The second and third field campaigns were carried out between December 19 and 21, 2016 (base flow) and during the period January 31, 2017 to February 3, 2017 (rainy season), respectively and focused on water sample collection. The second field campaign was carried out under base flow conditions before the beginning of the rainy season whereas the third campaign was representative of wetter, possibly recharge conditions because it was carried out during the rainy season. During the second field campaign (base flow), samples from springs, river and groundwater were collected for chemical and isotopic analysis, and groundwater was sampled from boreholes drilled as part of the hydrogeological investigation in the study area (Arcadis, 2017). A sampling location map is presented in Figure 2. During the third campaign (rainy season), samples of river water and a larger number of springs were collected for chemical and isotope analysis. A sampling location map for the third campaign is presented in Figure 3. Also during the third campaign a survey of all the springs found on the northern flank of the ravine in the upper course of river was also performed and in situ parameters including pH, electrical conductivity and temperature were also measured (Table 3). A location map showing the spring sites is presented in Figure 4. The sampling protocol including materials used in the sampling is described in Appendix A, pictures of some of the sampling locations are presented in Appendix B, and the analytical methods are detailed in Appendix C. The chemical analysis included major cations and anions. The anions were determined by ion chromatography (chloride, sulfate, nitrate) (Cl-, SO42-, NO3-) and volumetric titration (bicarbonate) (HCO3-), and cations (sodium, potassium, calcium, magnesium) (Na+, K+ ,Ca2+, Mg2+) by plasma emission spectrometry (ICP-OES). The isotope analysis included oxygen-18 (18O) and deuterium (2H), tritium (3H) and carbon 14 (14C). The chemical analysis was performed at the ALS Laboratory in Chile and the isotope analyses were carried out at IT2 Isotope Tracer Technologies Inc. in Canada. The chemical data are presented in Tables 1 and 2 and the isotope data are reported in Tables 4, 5, 6 and 7. 1.5 Structure of the report Chapter 2 provides a description and discussion of the river, spring and groundwater hydrochemistry from the two sampling campaigns. The discussions focus on salinity patterns and the chemical composition of the different water types analyzed in the study. 496
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4
Then, the stable isotopic composition of these waters is presented for each campaign.
Here the discussion focuses on the differences between the isotopic signatures of the
river, springs and groundwater and their possible relationship to local and regional
recharge. The tritium and Carbon 14 data are also presented and discussed in Chapter 2,
within the context of the conceptual model of the river-groundwater interaction in the
Silala River basin system. Chapter 3 details the conclusions drawn from the study where
all the data and information are integrated and a conceptual model for the rivergroundwater
interaction is proposed. Details of the sampling methods are reported in
Appendix A whereas pictures recording some sampling activities are part of Appendix
B. Detailed information about analytical methods is described in Appendix C and
finally the official isotope data reported by the laboratory are presented in Appendix D.
The official chemical data is reported in Appendix E.
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497
5 Figure 2. Location of samples collected during the second campaign (base flow), December 2016. 498
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6
Figure 3. Location of samples collected during the third campaign (rainy season), January-
February 2017.
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499
7 Figure 4. Location map of the spring survey in the upper river course 500
Annex III
Sample ID
Coordinates
Date
Sampling depth (m.b.g.l.)
Water
type
T°C
pHlab
EClab
Alkalinity
Cl
SO4
HCO3
Ca
Mg
K
Si
Na
NO3
x
y
(μS/cm)
(mg/l of CaCO3)
mg/l
mg/l
mg/l
mg/l
mg/l
mg/l
mg/l
mg/l
mg/l
R-SI2-16
600242
7565357
20-12-2016
River
17.5
8.67
204.8
91
2,34
5,92
91,622
9,90
4,099
2,500
18,80
19,74
0,19
R-Río 1-16
599410
7564117
21-12-2016
River
14.5
8.09
175.7
104
4,55
7,40
93,818
9,80
4,014
2,780
21,90
18,07
0,25
SP-SI1-16
599943
7564936
20-12-2016
Spring
15.2
7.76
189.7
77
2,13
6,11
92,72
10,34
4,293
2,960
22,00
16,75
0,33
SP-SI05-16
597518
7564344
21-12-2016
Spring
20.3
7.01
88,3
25
1,28
8,26
30,378
3,93
0,646
2,910
21,40
10,37
0,27
PW-DQN-SI-16
599090
7563871
21-12-2016
Well
20.7
7.58
315
150
1,86
9,80
170,312
21,89
10,300
5,070
30,70
21,09
0,32
PW-BO-A-16
600185
7565278
21-12-2016
50
Ground
water
18.9
7.80
382
5,86
9,80
206,912
24,99
13,900
5,110
29,30
26,70
0,35
PW-BO-B-16
600185
7565278
21-12-2016
75
Ground
water
17.7
7.38
354
152
5,36
11,03
201,178
24,90
12,700
4,990
28,00
24,79
0,30
CW-BO-A-16
600175
7565267
21-12-2016
55
Ground
water
16.9
7.53
356
148
7,29
13,69
181,78
21,57
11,890
4,900
29,60
26,12
0,58
CW-BO-B-16
600175
7565267
21-12-2016
110
Ground
water
16
7.49
345
147
6,48
17,13
179,218
22,09
11,660
4,810
29,10
26,51
0,56
PW-UQN-A-16
599346
7564063
21-12-2016
40
Ground
water
19.4
7.48
321
147
2,19
10,35
183,854
23,11
10,470
5,610
32,80
21,97
0,28
PW-UQN-B-16
599346
7564063
22-12-2016
75
Ground
water
20.1
7.56
327
168
4,65
11,33
187,514
22,99
10,440
5,550
32,20
21,73
0,31
MWL-UQN-A-16
600175
7565267
22-12-2016
50
Ground
water
20.3
7.46
319
110
5,35
11,57
181,78
22,69
10,020
5,390
32,10
21,31
0,31
8
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501
PW-DQN-A-16
598839
7563780
22-12-2016
45
Ground
water
17.4
7.47
255.6
3,50
17,75
128,344
16,32
7,567
4,160
25,80
21,12
0,31
PW-DQN-B-16
598839
7563780
22-12-2016
35
Ground
water
17.7
7.34
262.3
102
3,39
19,00
129,93
16,45
7,302
4,230
27,20
20,50
0,29
MW-DQN-A-16
598841
7563769
22-12-2016
35
Ground
water
19.5
7.41
288.3
137
2,58
11,73
167,14
20,93
9,243
5,220
28,50
22,06
0,29
Table 1. Location, field parameters and chemical data for the second campaign.
9
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Annex III
Sample ID
Coordinates
Date
Water type
T °C
pH lab
EC lab
Alkalinity
Cl
SO4
HCO3
Ca
Mg
K
Si
Na
NO3
x
y
(μS/cm)
(mg/l of CaCO3)
mg/l
mg/l
mg/l
mg/l
mg/l
mg/l
mg/l
mg/l
mg/l
R-SI-2-17
600227
7565333
31-01-2017
River
17.1
8.6
186.7
66
2,36
6,27
95.6
8,37
3,633
2,010
22,10
17,44
0,22
R-SI-3-17
599184
7563959
01-02-2017
River
18.3
7.9
181.3
22
2,31
6,48
91.6
9,29
3,664
2,440
19,80
16,56
0,23
R-SI-4-17
597908
7564081
01-02-2017
River
20.8
8.6
260.3
96
1,99
7,89
133
16,04
7,164
3,740
25,90
18,39
0,24
R-SI-7-17
596611
7563887
01-02-2017
River
18.4
8.7
243.9
119
1,92
9,33
115
14,42
6,407
3,550
25,30
17,16
0,19
SP-SI-1-17
599956
7564952
31-01-2017
Spring
15.2
7.6
182.9
63
2,12
6,64
100
9,96
4,106
2,710
21,70
15,97
0,35
SP-SI-5-17
597517
7564342
01-02-2017
Spring
20.2
7.8
88.2
48
1,24
8,19
34
3,79
0,563
2,570
21,90
9,41
0,29
SP-SI-8-17
596886
7564854
01-02-2017
Spring
19.2
7.2
95.3
25
1,18
11,50
31
3,95
0,489
2,250
20,40
10,66
0,24
SP-SI-9-17
597091
7564257
01-02-2017
Spring
18.5
7.2
92.1
64
1,09
9,72
32
4,24
0,525
2,580
21,10
9,77
0,21
SP-SI-10-17
600098
7563292
01-02-2017
Spring
13.6
7.9
228.4
74
2,16
14,88
99
14,63
6,294
6,680
30,60
11,86
0,22
SP-SI-15-17
599926
7564847
31-01-2017
Spring
15.6
7.9
161.2
43
2,09
6,24
76
8,45
3,090
2,360
19,70
14,88
0,35
SP-SI-16-17
599927
7564885
31-01-2017
Spring
15.5
7.9
150.9
48
2,09
5,94
73
7,06
2,550
2,040
23,00
13,52
0,36
SP-SI-17-17
599871
7564761
31-01-2017
Spring
15.1
7.9
136.5
28
2,06
5,81
68
6,54
2,119
2,120
18,60
13,66
0,34
SP-SI-18-17
599765
7564582
31-01-2017
Spring
15.6
7.8
140.4
19
2,06
6,08
62
6,12
2,175
1,960
22,90
12,91
0,34
SP-SI-19-17
599609
7564354
31-01-2017
Spring
16.1
7.8
139.8
28
2,04
5,94
66
6,60
2,463
2,060
19,60
13,35
0,34
SP-SI-27-17
599611
7564360
31-01-2017
Spring
16.6
7.8
158.7
83
2,03
6,52
74
7,66
3,107
2,180
23,80
14,02
0,33
SP-SI-28-17
599825
7564812
31-01-2017
Spring
11.5
7.6
176.3
17
2,13
7,10
87
9,60
3,908
2,630
22,00
15,45
0,34
SP-SI-29-17
598290
7563892
01-02-2017
Spring
21.5
7.6
167.3
44
2,01
6,28
78
8,59
2,762
2,810
19,60
14,81
0,31
SP-SI-31-17
596773
7563900
02-02-2017
Spring
19.1
7.9
192.7
75
2,32
6,55
82
8,73
2,907
3,710
26,60
16,17
0,44
Table 2. Location, field parameters and chemical data for the third campaign.
10
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perched11 WGS84 Field Parameters ID X Y Date Altitude pH Temperature (°C) Conductivity (μS/cm) SP-FCAB-1 599926 7564847 31-01-2017 4320 8.11 15.6 131 SP-FCAB-2 599932 7564890 02-02-2017 4194 8.19 14.7 161 SP-FCAB-3 599927 7564861 02-02-2017 4268 8.21 15.2 151 SP-FCAB-4 599914 7564899 02-02-2017 4269 8.36 15.4 106 SP-FCAB-5 599915 7564886 02-02-2017 4275 8.24 15.6 98 SP-FCAB-6 599954 7564869 02-02-2017 4297 8.34 15.1 131 SP-FCAB-7 599890 7564829 02-02-2017 4272 8.34 15.4 133.4 SP-FCAB-8 599893 7564824 02-02-2017 4270 8.42 16 122 SP-FCAB-9 599897 7564808 02-02-2017 4257 8.34 15.4 105 SP-FCAB-10 599874 7564755 02-02-2017 4254 8.38 15.9 125 SP-FCAB-11 599900 7564740 02-02-2017 4268 8.48 15.9 115 SP-FCAB-12 599927 7564737 02-02-2017 4301 8.38 15.2 124 SP-FCAB-13 599845 7564627 02-02-2017 4242 8.38 16.1 131 SP-FCAB-14 599802 7564619 02-02-2017 4243 8.48 15.9 122 SP-FCAB-15 599797 7564611 02-02-2017 4240 7.95 13.72 140 SP-NN1 599919 7564845 02-02-2017 4259 8.15 14.1 111 SP-NN2 599895 7564799 02-02-2017 4247 8.41 16.1 118 Table 3. Location of springs survey and field parameters, third campaign.
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2. RESULTS AND DISCUSSION
2.1 Geochemistry Data
In order to facilitate the discussion of the data, the study area was divided into the upper
and lower course of the river, which correspond to the zones above and below the
Quebrada Negra (Figure 1). The Silala River and the springs in the study area are
generally characterized by low conductivity values ranging between 84 and 290 μS/cm
(Tables 1 and 2). The waters of springs located in the upper part of the Silala River
course have a relative higher mineralization, with values of electrical conductivities
(EC) ranging between 100 and 189.7 μS/cm, compared to the springs located in the
northern part of the lower course of the river Silala which present EC values ranging
between 88.3 and 95.3 μS/cm (Tables 1 and 2). This pattern was observed in both the
second (base flow condition) and third (wet condition during the rainy season)
campaigns.
The Silala River, with EC values ranging between 175.7 and 260.3 μS/cm, presents a
similar degree of salinity to the springs located in the upper course of the river Silala,
like SP-SI1-16 (Figure 2); SP-SI-17-17, SP-SI-16-17, SP-SI-18-17 (Figure 3). The
groundwaters from the second campaign borehole sampling with EC values ranging
between 255.6 and 382 μS/cm, are characterized by higher EC values than either the
springs or the river. (Tables 1 and 2). The spring survey (Figure 4) also showed that the
spring system in the higher part of the river course has much lower EC values (Table 3)
than the groundwater in the deep aquifer.
The Silala River and the springs are mainly Sodium (Na)-Bicarbonate type water with
relative high content of Ca and no significant differences are observed between the
springs located in the upper or lower part of the river course. The water chemical
composition can be visualized using Stiff diagrams (Figures 5 and 6). The Stiff diagram
consists of a polygonal shape of four parallel horizontal axes extending on either side of
a vertical zero axis. Cations are plotted in milliequivalents on the left side of the zero
axes, one to each horizontal axis, and anions are plotted on the right side. The
groundwaters, which are Calcium (Ca)-Bicarbonate type water, tend to have a different
chemical composition to the river and spring waters. The high Na and Ca content is
probably related to weathering of silicate minerals, which is supported by the high silica
content of these waters, which ranges between 18 and 37 mg/l (Table 1 and 2).
The chemical data have shown that the spring system located near the river in the upper
part of the river course does not have the chemical fingerprint associated with
groundwater discharge of the deep, perhaps regional, aquifer system. This pattern
suggests that the springs are part of a subsurface flow system associated with a perched
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505
13 aquifer, which drains into the river. The chemical data does not preclude the possible influence of local recharge for the spring system and the river, and the chemistry of the river and springs along the river are clearly related. Figure 5. The Stiff diagrams of water samples collected during the second campaign in the Silala River basin. 506
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Figure 6. The Stiff diagrams of water samples collected during the third campaign in the Silala
River basin.
2.2 Environmental isotope data
This section deals with the evaluation of environmental isotope data collected from the
springs, river and groundwater in the study area. The stable isotopes used in this
research correspond to 18O, 2H and 13C, while the radioactive isotopes were tritium (13H)
and carbon 14 (14C). The stable isotopes, which are part of the water molecule, provide
information about the origin of groundwater, therefore are used for evaluation of
recharge areas, and 3H and 14C provide information about groundwater residence time.
13C provides information about geochemical reactions that can affect the dissolved
inorganic carbon (DIC) along the groundwater flow system (Clark and Fritz, 1997).
These tracers have been extensively used in groundwater studies in Northern Chile
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15 (Magaritz et al., 1989; Aravena and Suzuki, 1990; Herrera et al., 2006; Uribe et al., 2015). 2.2.1 δ18O and δ2H data One key aspect that needs be constrained to allow the interpretation of the isotope data using the typical diagram of δ 2H vs δ18O is the local meteoric water line, which is a reflection of the isotopic composition of the precipitation in the study area. A description of the preparation of the local meteoric water line is described below. The isotopic characterization of precipitation has been made using data corresponding to the city of La Paz for the period 1995-2009 (International Atomic Energy Agency (IAEA) and from precipitation data corresponding to different locations in northern Chile. Most of the northern Chile data were obtained from Aravena et al. (1999), which correspond to locations higher than 4.000 m.a.s.l. Precipitation data from the city of La Paz have been used because of its continuous monitoring of the precipitation isotopic composition (IAEA / World Meteorological Organization (WMO)) and the large amount of information available for the different months of the year. All samples show a good correlation between δ18O and δ2H at all sampling points, regardless of the proximity to the study area. Having discarded the rain samples that were suspected of being affected by evaporation, a local meteorological line has been calculated by linear interpolation using least squares which has the following expression: δ2H= 7.9δ18O + 14.One key characteristic of the precipitation in Northern Chile is the existence of anisotopic gradient with altitude where the high altitude rainfall tends to be isotopically more depleted than rainfall at lower altitude (Fritz et al., 1981; Chaffaut, 1998; Aravena et al., 1999; Uribe et al., 2015). This explains the rationale behind the use of environmental isotopes in water resources studies in the Northern Chile, Bolivian and Peruvian Altiplano regions. The isotope data for the river, springs and groundwater collected for the second and third campaigns are reported in Tables 4 and 5, respectively. Figure 7a and Figure 7b show these data compared with the global meteoric water line (δ2H = 8δ18O + 10) and the local meteoric water line (δ2H = 7,9δ18O + 14). A clear pattern is observed in these data. The springs located in the upper course of the river have a different isotope fingerprint to the springs located in the northern part of the lower course of the river (Figure 7a). The lower course springs are plotted near the local meteoric water line with higher deuterium excess values (around 15 ‰) where the upper springs are located below the local meteoric water line. Based on the isotope data, the springs in the northern part of the lower course of the river should represent local recharge. The isotopic pattern observed in the second campaign was confirmed in the third campaign 508
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16
where more springs of the lower and upper course of the river were collected (Figure
7b). Furthermore, the data collected in the third campaign showed that some springs
located in the southern part of the lower river course showed a similar isotopic
fingerprint to the upper river course springs. This pattern suggests that these springs are
part of the same hydrogeological system that generates the springs in the upper course
of the river and/or part of a subsurface flow system fed by groundwater discharge
associated with the Quebrada Negra valley, represented by the spring SP-SI-10-17
(Figure 3), which has an isotopic composition in the range of the upper river course
springs (Figure 7b).
Concerning the river waters, they have a similar isotopic fingerprint to the upper springs
and the lower springs located in the southern part of the river (Tables 4 and 5), therefore
they plotted in the same group. This is observed in the data collected in both campaigns
(Figures 6a and 6b). The isotope data indicated that both types of water have a similar
origin. The isotopic data for the groundwater in both campaigns also plotted as part of
the river and upper springs group, which suggest that all these waters are associated
with recharge areas at similar altitudes. The isotope composition of these waters all
plotted below the local meteoric water line, which is a typical feature for groundwater
and springs in Northern Chile (Fritz et al., 1981; Magaritz et al., 1989; Uribe et al.,
2015). This pattern has been associated with evaporation during the waters’ residence
time in the unsaturated zone (Magaritz et al., 1989). Therefore, assuming a slope of 3
for the evaporation line in soil (Clark and Fritz, 1997) and extrapolating the data using
this slope, the evaporation line would intersect the local meteoric water line around -
14,5 ‰ of δ18O, which is within the range of isotope values measured for precipitation
above 3,500 m.a.s.l. (Aravena et al., 1999; Uribe et al., 2015).
The isotope data indicate that the river, the upper springs and the groundwater are part
of a regional flow system recharged in the high Andes of Bolivia and Chile.
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509
17 Sample ID Water type δ18O VSMOW (‰) δ2H VSMOW (‰) R-SI-02-16 River -11.5 -92 R-Río 1-16 River -11.5 -91 SP-SI-01-16 Spring -11.7 -92 SP-SI-21-16 Spring -11 -82 SP-SI-05-16 Spring -11.5 -83 PW-DQN-SI-16 Well -11.9 -93 PW-BO-A-16 Groundwater -11.9 -94 PW-BO-B-16 Groundwater -11.9 -93 CW-BO-A-16 Groundwater -11.9 -94 CW-BO-B-16 Groundwater -11.9 -94 PW-UQN-A-16 Groundwater -12 -93 PW-UQN-B-16 Groundwater -11.9 -93 MWL-UQN-A-16 Groundwater -11.9 -93 PW-DQN-A-16 Groundwater -11.7 -92 PW-DQN-B-16 Groundwater -11.8 -92 MWL-DQN-A-16 Groundwater -11.9 -93 Table 4. Stable isotopes results of second campaign samples. 510
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18
Sample ID Water type δ18O (VSMOW ‰) δ2H (VSMOW ‰)
R-SI-2-17 River -11.6 -93
R-SI-3-17 River -11.6 -92
SP-SI-1-17 Spring -11.8 -93
SP-SI-5-17 Spring -11.7 -83
SP-SI-8-17 Spring -12 -84
SP-SI-9-17 Spring -12 -84
SP-SI-10-17 Spring -11.7 -90
SP-SI-15-17 Spring -11.8 -92
SP-SI-16-17 Spring -11.8 -92
SP-SI-17-17 Spring -11.8 -92
SP-SI-18-17 Spring -11.8 -92
SP-SI-19-17 Spring -11.8 -92
SP-SI-27-17 Spring -11.8 -92
SP-SI-28-17 Spring -11.8 -92
SP-SI-29-17 Spring -11.7 -91
SP-SI-31-17 Spring -11.7 -90
Table 5. Stable isotope results of the third campaign samples.
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19 Figure 7. a) Plot of δ18O and δ2H for river, spring water, and wells (second campaign) b) Plot of δ18O and δ2H of river and spring water (third campaign). LML: Local meteoric line. GML: a) b) 512
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20
Global Meteoric Line. The solid black line represents an evaporation line with slope of 3 in
both cases.
Based on the isotope and chemical data it is clear that the river and upper spring waters
could be closely related. It seems likely that the origins are from recharge to a perched
series of aquifers overlying the Silala Ignimbrite and possibly the Cabana Ignimbrite
and the widespread andesitic lava flow (SERNAGEOMIN, 2017) that forms the eastern
edge of the Orientales wetland. The water stored in these subsurface perched units
moves through alluvial deposits (see Arcadis, 2017 and SERNAGEOMIN, 2017) or
horizontal fractures in the ignimbrites. The water level data obtained in the new wells
drilled in the deeper aquifer, as part of the hydrogeological investigation (Arcadis,
2017), which showed the water level in the aquifer is lower than the river water level,
tends to support this hypothesis. Figure 8 shows the general situation of the catchment
with the springs and mountains that edge the Silala River.
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513
21 Figure 8. Catchment, springs and Silala River. 2.2.2. Tritium Data The interpretation of tritium data in groundwater requires a reconstruction of the tritium content of the precipitation during the last seven decades. One of the difficulties in constructing the tritium input function in the study area is the lack of continuous monitoring of tritium activity in rainwater from 1954 to the present. In South America, there is no observation station with a continuous series of data. The most complete data are from Porto Alegre and Río de Janeiro, which are part of the International Atomic Energy Agency (IAEA) monitoring network. There are four observation stations at a 514
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22
latitude relatively close to the Silala area. These are Cuzco (3,246 m.a.s.l.) in Perú, La
Paz (4,071 m.a.s.l.) in Bolivia, and Los Molinos (1,300 m.a.s.l.) and Salta (1,187
m.a.s.l.) in Argentina (Herrera et al., 2006) (Figure 9). However, in order to reproduce
the tritium input function, it is necessary to know its concentrations in rainwater since
1953, when thermonuclear tests were initiated in the atmosphere. The period between
1954 and 1968 of the series was completed with tritium data from Porto Alegre and Río
de Janeiro, Brazil. The tritium input function for the southern Hemisphere is presented
in Figure 9. Based on this figure the tritium data for recent precipitation in the study
area should be between 3 and 5 TU.
Figure 9. Concentrations of monthly rainwater tritium measured at IAEA stations in the
Southern Hemisphere in South America (Herrera et al., 2006).
1957
1959
1961
1963
1965
1967
1969
1971
1973
1975
1977
1979
1981
1983
1985
1987
1989
1991
1993
1995
1997
1999
2001
2003
0
10
20
30
40
50
60
70
80
90
100
Porto Alegre
Cuzco
Salta
Los Molinos
La Paz
Leyenda
TRITIO (UT)
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515
23 The tritium data for both campaigns are presented in Table 6. These data showed that the springs, river water and groundwater basically do not contain tritium, indicating that these waters were recharged before the 1960s. Sample ID Collection Date TU Water type ± 1σ PW-BO-B-16 21-12-2016 <0.05 Groundwater 0.23 PW-UQN-B-16 22-12-2016 0.07 Groundwater 0.23 PW-DQN-B-16 22-12-2016 0.22 Groundwater 0.23 R-SI-02-16 20-12-2016 0.16 River 0.23 SP-SI-21-16 21-12-2016 0.18 Spring 0.22 SP-SI-05-16 21-12-2016 < 0.05 Spring 0.19 SP-SI-8-17 01-02-2017 <0.05 Spring 0.2 SP-SI-15-17 31-01-2017 0.31 Spring 0.29 SP-SI-10-17 01-02-2017 <0.05 Spring 0.11 R-SI.7-17 01-02-2017 <0.05 River 0.31 Table 6. Tritium data. 2.2.3 Carbon-14 and Carbon 13-Data By convention, the radiocarbon dating technique assumes that the 14C content of the atmospheric carbon dioxide (CO2) was 100 percent modern carbon (pMC) and has been constant in the past. For example, if a sample of wood has a 14C content of 50 pMC, which corresponds to half of the initial 14C of the atmospheric CO2 and based on the 14C half life of 5730 years, it can be estimated that the wood sample has a radiocarbon age of 5730 years. In the case of groundwater, the 14C gets into the groundwater during dissolution of soil CO2 during recharge events. The soil CO2 has a 14C content of 100 pMC but during groundwater flow in the aquifer, the 14C content can be affected by the input of old carbon, for example from dissolution of carbonate, from old organic carbon involved in redox processes such as sulfate reduction or input of volcanic CO2 in volcanic areas (Clark and Fritz, 1997). The 13C data provide information about processes and input of old carbon to the dissolved inorganic carbon along the groundwater flow system. δ13C values for soil CO2 in the recharge areas of arid environments can be around -18 ‰ (Fritz et al., 1981). The δ13C values for ground water range between -7.3 and -8.0 ‰, the river showed a value 516
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24
of -8.0 ‰ during base flow conditions and the spring located in the northern part of the
lower river course showed a δ13C value of -7 ‰ (Table 7). A slightly more depleted
δ13C value of -9 ‰ was observed in in the river during the rainy season and the springs
showed δ13C values between -5.7 and -6.8 ‰ (Table 8). The δ13C enrichment pattern
observed in the dissolved inorganic carbon compared to the expected δ13C value for
CO2 in the recharge area should be associated with dissolution of carbonates minerals
during groundwater flow in the aquifer. Carbonates minerals tend to have δ13C values
close to 0 ‰ (Clark and Fritz, 1997). This also should be reflected in the 14C content,
which will be influenced by the input of old carbon from dissolution of carbonates
minerals and radioactive decay during groundwater flow in the aquifer. For this study,
the C-14 data will not be used to estimate water residence time and it will only be used
as a tracer to evaluate the river-groundwater interactions and river-springs interactions.
The 14C data for both campaigns are reported in Table 7. These data show that the
lowest values are observed in groundwater collected in the deep boreholes, which is
characterized by values of 9.5 and 14.5 pMC. The river at the sampling site near the
border has a 14C value of 26.6 pMC collected during base flow before the rainy season
and changes to a value of 45.9 pMC in a downstream location during the rainy season
(Figure 10). The 14C value during the rainy season can be related to some contribution
of recent groundwater associated with recent precipitation which is supported by an
increase in river flow during the rainy season (Suárez et al., 2017). However, because of
the almost nil concentration of tritium in these waters, it is probably that the
contribution of new water is small. One spring (SP-SI-15-17) from the higher part of the
river course has a value of 32.4 pMC, which is near the 14C content of the river during
baseflow conditions. This suggests that the flow system feeding the springs is not made
up of new, very recent recharge associated with recent precipitation. The spring located
in the Quebrada Negra, which represents discharge of a regional flow system, perhaps
recharged at higher altitude in Bolivia, has a 14C value of 30 pMC. The springs located
in the northern lower part of the river course, which represent local recharge have much
higher 14C content than the rest of the water with a value of 76.9 pMC in the first
campaign, which is confirmed by a value of 78 pMC in the second campaign (Table 7,
Figure 10). The 14C data tend to confirm the interpretation based on the stable isotope
data in water that the springs of the perched aquifer and the river are part of a regional
flow system recharged in the high areas of Bolivia and Chile and have spent some time
in storage.
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517
25 ID sample Water Type δ 13C (PDB) 14C DIC pMC ± 1σ R-SI2-16 River -8 26.66 0.13 SP-SI05-16 Spring -7 76.86 0.35 PW-BO-B-16 Groundwater -7.3 9.93 0.08 PW-UQN-B-16 Groundwater -8 14.54 0.09 R-SI-3-17* River -9.1 45.97 0.27 SP-SI-8-17* Spring -6.8 78.39 0.24 SP-SI-15-17* Spring -5.8 32.41 0.15 SP-SI-10-17* Spring -6.7 30.06 0.15 Table 7. C-14 data for river, springs and groundwater. First and second* campaign. The sampling points distribution is presented in Figure 10. 518
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26
Figure 10. Distribution of 14C sampling points in the Silala River basin. This figure is
complemented by Table 7, which contains the sample point values.
3. CONCLUSIONS
The chemical data show that the river, springs and groundwater are characterized by
low salinity. The springs in the high part of the river course tend to be more saline than
the springs located in the lower northern part of the river course. The river has similar
salinity to the upper springs and the groundwater has a higher salinity than the river and
springs. In general, the water is Na-bicarbonate type with differing degrees of Ca
content. The groundwater is Ca-bicarbonate type. The high silicate content of these
water indicated that the main source of the chemical composition of the water is
weathering of silicate minerals. The chemical data suggest that the springs in the upper
part of the river course are not a reflection of groundwater discharge from the deeper
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519
27 aquifer, indicating that probably the springs emerge from a subsurface flow associated with a perched aquifer. The isotope data showed that the springs located in the lower northern part of the river course have a different isotopic fingerprint to the springs located in the upper course of the river. The river water has a similar isotopic pattern to the upper springs indicating they have a similar origin. Furthermore, the isotope data showed the springs located in the lower southern part of the river might be similar in origin to the springs located in the upper river course. This may indicate that they are part of the same hydrogeological system and/or part of subsurface flow system fed by a regional groundwater flow system that has a very small discharge in the upper Quebrada Negra. Concerning the groundwater, they have a similar isotope composition to the upper springs and the river. This is interpreted as indicating that these waters were recharged from precipitation falling at a similar altitude. Based on the chemical and isotope data, visual observation in the field and water level data in the new wells compared to the river, this information tends to confirm the hypothesis that the upper springs are discharging features of a perched aquifer and that the deep water characterized in the new wells would corresponds to a regional aquifer in the volcanic rock. The tritium data in upper and lower springs, groundwater and river water show that the tritium concentration is practically nil indicating these waters are not likely to be recent. Concerning the 14C data, a wide range in values is observed in these data. The springs representing the lower northern course of the Silala River, which appear to represent local recharge, showed values near 77 pMC. Much lower 14C content is observed in the groundwater, with values of 14.5 and 9.9 pMC in water collected in the new wells and in the river with a value of 26.6 pMC. The river value increases to 45.9 pMC during the rainy season, indicating some contribution of recent groundwater into the river, which is related to precipitation events during the rainy season. The C-14 data of 32 pMC obtained for the upper springs which is near the C-14 value of the river during base flow condition, support the conceptual model postulated based on the isotope, chemical and hydrogeological data. This model includes an interaction between a perched aquifer, probably in alluvial deposits on the flanks of the high mountains, and the river as result of a complex system of fractures present in the ignimbrites. These waters are likely be part of a regional flow system recharged in the high Andes of Bolivia and the flanks of the Volcán Apagado and Cerro Inacaliri in Chile. 520
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4. REFERENCES
Aravena, R., and Suzuki, O., 1990. Isotopic evolution of rivers in northern Chile. Water
Resources Research, 26 (12), 2887-2895.
Aravena, R., Suzuki, O., Peña, H., Pollastri, A., Fuenzalida, H., Grilli, A., 1999.
Isotopic composition and origin of the precipitation in northern Chile. Applied
Geochemistry 14 (4), 411-422.
Arcadis, 2017. Detailed Hydrogeological Study of the Silala River. (Vol. 4, Annex II).
Chaffaut, I., 1998. Precipitations d'Altitude, Eau Souterraines et Changements
Climatiques de L'Altiplano Nord-Chilien. Universite de Paris Sud U.F.R. Scientifique
D'Orsay, Paris, France.
Clark, I.D. and Fritz, P., 1997. Environmental Isotopes in Hydrogeology. Lewis
Publishers, Boca Raton, Florida, p. 342.
Fritz, P., Suzuki. O., Silva. C., and Salati. E., 1981. Isotope hydrology of groundwaters
in the Pampa del Tamarugal, Chile. Journal of Hydrology 53, 161-184.
Latorre, C., Frugone, M., 2017. Holocene Sedimentary History of the Río Silala
(Antofagasta Region, Chile). (Vol. 5, Annex IV).
Herrera, C., Pueyo, J., Sáez, A. & Valero-Garcés, B., 2006. Relación de aguas
superficiales y subterráneas en el área del lago Chungará y lagunas de Cotacotani, norte
de Chile: Un estudio isotópico. Revista Geológica de Chile, 33 (2), 299-325.
IAEA/WMO, 2015. Global Network of Isotopes in Precipitation. The GNIP Database
(Available at: http://www.iaea.org/water).
Magaritz, M., Aravena, R., Pena, H., Suzuki, O., and Grilli, A., 1989. Water chemistry
and isotope study of streams and springs in northern Chile. Journal of Hydrology, 108,
323-341.
SERNAGEOMIN (National Geology and Mining Service), 2017. Geology of the Silala
River Basin. (Vol. 5, Annex VIII).
Suárez, F., Sandoval, V., Sarabia, A., 2017. River-Aquifer Interactions Using Heat as a
Tracer in the Transboundary Basin of the Silala River. (Vol. 5, Annex X).
Uribe, J., Muñoz, J.F., Gironás, J., Oyarzún, R., Aguirre, E., and Aravena, R., 2015.
Assessing groundwater recharge in an Andean closed basin using isotopic
characterization and a rainfall-runoff model: Salar del Huasco basin, Chile.
Hydrogeology Journal, 23, 1535-1551.
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APPENDIX A
Materials used in the sampling events included:
• Notebook and pencil.
• Containers for sampling.
• Ice Packs.
• Transparent adhesive tape.
• Scissors.
• Container or bottle for measurements of physical and chemical parameters in situ.
• Equipment for in situ measurements (pH meter, conductivity meter, thermometer).
• Replacement batteries.
• Measuring tape.
• Photographic camera.
• Bailer for manual sampling with rope (optional).
• Submersible pump, controller and generator in case the sampling is carried out
through the well drain.
• Latex gloves.
• Distilled water for the washing of the multiparameter probes.
The containers used for each sampling point is listed below as a reference.
• 1 plastic container of 1000 mL without additives, labelled for analysis of General
Parameters.
• 1 plastic container of 500 - 1000 mL with additive included (H2SO4) inside, labelled
for nutrient analysis.
• 1 plastic container of 500 mL with additive included (NaOH) inside, labelled for
cyanide analysis.
• 1 500 mL plastic container with additive included (HNO3) inside, labelled for total
metal analysis.
• 1 plastic container of 250 - 500 mL without additives, labelled for total suspended
solids (SST) analysis.
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31 • 1 plastic container of 250 mL without additives, labelled for analysis of dissolved metals. • 1 plastic container with double lid of 100 - 250 mL, without additives, labelled for isotopic analysis of deuterium (δ2H) and oxygen (δ18O) of the water. Each of these containers was labelled with the following information: • Name of the sample. • Date of sampling. • Place of sampling (basin or place name or coordinates, etc.). • Type of sample (groundwater / surface / residual / precipitation / etc.). At each of the sampling points mentioned above, the following in situ parameters were measured: • pH. • Conductivity. • Alkalinity. • Temperature. After sampling, the following information was entered on a spreadsheet: • Sampling time. • Indicate the characteristics of the sample taken, whether it is filtered or not, and whether it contains preservatives or additives, and label with the type of additive. • The label of each container is protected with thick transparent tape to prevent it from getting wet and deforming or erasing the labelled information. The field pH measurement was performed using a Hanna portable pH / mV meter, model HI9124, which has a precision range of ± 0.01 pH unit. The same equipment was used to measure temperature, which has a precision range of ± 0.4 °C. The equipment was calibrated before obtaining the first sample of each day, using two buffers, 4 and 7. The field conductivity was measured using a Hanna multi-range portable conductivity meter with waterproof temperature compensation, model HI-9033. This equipment has a precision range of ± 1%. Finally, the alkalinity was measured with the "Digital Tester - Water Alkalinity Checker HI772", which performs the measurements using the colorimetric method. Since this alkalinity measurement methodology is not validated, the value obtained in the field will only be used as a reference and for with that obtained in the laboratory and by the modeling considering the concentrations of HCO3. For 524
Annex III Appendix A
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water filtration, a 0.45 mm filter was used, along with a Geotech Geopump ™ Series I
and II peristaltic pump, which are designed for single or multiple stage pressure or
liquid suction.
In the case of carbon 14 sampling, these steps were followed:
• The water was taken from the mouth of the well, spring or river.
• Before collecting the sample, the water was allowed to flow for a sufficient time so
that the collected water comes directly from the aquifer / spring/river.
• The bottle was filled but leaving the neck of the bottle empty to allow the liquid to
expand during transport. During this step the peristaltic pump with the filter was used.
• Adhesive tape was placed around the cap to prevent exchange or loss of CO2 from the
water.
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33 526
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APPENDIX B
Pictures of the sampling locations for the second field campaign:
Picture 1. Sampling of the spring SP-SI-5-17. The up gradient area was under vegetation, so the
whole sample set was filtered using the peristaltic pump to avoid any type of contamination.
Picture 2. The Silala River sample point just across the Chile-Bolivia boundary, in Chile.
Annex III Appendix B
527
35 Pictures of some of the sampling locations for the third field campaign: Picture 3. R-SI-7-17 sampling point. Picture 4. SP-SI-8-17 sampling point. 528
Annex III Appendix B
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Picture 5. SP-SI-9-17 sampling point.
Picture 6. SP-SI-16-17 sampling point.
Annex III Appendix B
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37 Picture 7. Spring SP-SI-2-17 sampling point. Picture 8. Spring SP-SI-5-17 sampling point. 530
Annex III Appendix B
38
APPENDIX C
The anions were determined by ion chromatography (Cl-, SO42-, NO3-) and volumetric
method (HCO3-), and cations by plasma emission spectrometry (ICP-OES). δ2H and
δ18O were measured on a gas-source isotope ratio mass spectrometer (Finnigan Delta S).
Water samples were analyzed for both oxygen and hydrogen isotopes in Isotope Tracer
Technologies, on a Picarro CRDS (Model L1102-i). The Picarro CRDS isotopic water
analyzers provides both δ18O and δ2H stable isotope ratios with high precision in one
fast measurement. The instrument is equipped with a high precision autosampler,
capable of making consistent small volume injections into the vaporizer. In addition, the
instrument is configured with a unique vaporization module that converts the liquid
water sample to the vapour phase in a flash process at 140 °C. The vapour is then
delivered into the CRDS cavity for analysis. This process avoids any possible
fractionation effects that may occur with other liquid/vapour transitions, such as
nebulizers. The Picarro analyzers are equipped with a thermally controlled optical
cavity that ensures minimal drift, even in the harshest environments. In addition, an
onboard wavelength monitor enables the absorption lines unique to H 2 16 O, H 2 18 O,
and HD 16 O to be scanned repeatedly, quickly and precisely.
Three to four calibrated internal standards are included at the beginning and end of
every run, as well as after every 10 samples. The employed internal standards have been
calibrated to VSMOW, GISP, and SLAP. The results are evaluated and corrected
against standards that bracket the samples, and then reported against the international
reference material. Precision is 1.0 per mil or better for δ2H and 0.1 per mil or better for
δ18O based on repeated internal standards.
Tritium was measured by liquid scintillation spectrometry on samples that were first
distilled to remove non-volatile solutes, and then enriched by electrolysis by a factor of
about 9. Enriched samples were mixed 1:1 with Ultimagold Low Level Tritium (R)
cocktail, and counted for 1500 minutes in a Quantulus 1220 Spectrometer in an
underground counting laboratory at the Isotope Trace Technologies. The detection limit
under these conditions is 0.6 TU. Standardization is relative to NIST SRM 4361C.
Tritium is reported in Tritium Units. 1TU = 3.221 Picocurries/l per IAEA, 2000 Report.
1TU = 0.11919 Becquerels/l per IAEA, 2000 Report.
Due to the large amount of dissolved sulfate and the low dissolved inorganic carbon
concentrations in water, the 14C content was determined by accelerator mass
spectrometry (AMS) in a USA laboratory. The CO2 was prepared at the Isotope Tracer
Technologies Laboratory and send to the AMS lab for analysis. AMS dating involves
accelerating the ions to extraordinarily high kinetic energies followed by mass analysis.
Annex III Appendix C
531
39 Samples are converted to graphite prior to AMS carbon dating. Although more expensive than radiometric dating, AMS dating has higher precision, and needs small sample sizes. The standard used was OX1: 1.05 x e-10, OX2: 1.35 x e-10, C6: 1.5 x e-10 and C7: 0.5 x e-10 and the typical standard deviation is 5 to 10% of Standard values. The 13C DIC analyses were measured using a Finnigan Mat, DeltaPlus XL IRMS in the Isotope Tracer Technologies, with a standard IT2-27 / IT2-34 / NBS-18/NBS-19 and a typical standard deviation of 0.2 per mil. 532
Annex III Appendix C
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APPENDIX D
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533
41 534
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42
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535
43 536
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45 538
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APPENDIX E
APPENDIX E
Second campaign results
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INFORME DE ENSAYO: 48774/2016Propuesta comercial: 15818/2016.3Arcadis Chile SPAAntonio Varas 621 - Providencia - SantiagoAtención: Ximena OrregoAnálisis Terreno SilalaMuestras recibidas el: 26/12/2016Informe generado el 12/01/2017Pág. 1 de 5 Hermanos Carrera Pinto #159, Parque Industrial Los Libertadores, Colina, Santiago, Chile | Telf +56 2 2654 6104
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INFORME DE ENSAYO: 48774/2016RESULTADOS ANALÍTICOS Muestras del Item: 1N° ALS483362/2016-1.0483364/2016-1.0Fecha de Muestreo22/12/201621/12/2016Hora de Muestreo13:40:0017:45:00Tipo de MuestraAguaSuperficialAguaSuperficialIdentificaciónSI2B-IRIOParámetroCMUnidadLDLQValoresValoresF, Fluoruro11551mg/L0,020,060,120,09Cl, Cloruro11551mg/L0,030,085,354,55ClO3, Clorato11551mg/L0,050,11<0,11<0,11Br, Bromuro11551mg/L0,050,10<0,10<0,10SO4, Sulfato11551mg/L0,160,1211,577,40N-NO2, Nitrito11551mg/L0,040,09<0,09<0,09N-NO3, Nitrato11551mg/L0,020,050,310,25P-PO4, Fosfato11551mg/L0,040,13<0,13<0,13Fecha de Análisis11551---------27/12/2016 10:0027/12/2016 10:00Conductividad Eléctrica11863μS/cm2,0---319,0175,7Fecha de Análisis11863---------28/12/2016 00:0028/12/2016 00:00Aluminio Disuelto (Al)12671mg/L---0,010,010,02Antimonio Disuelto (Sb)12671mg/L---0,00020,00040,0010Arsénico Disuelto (As)12671mg/L---0,00030,05410,1020Bario Disuelto (Ba)12671mg/L---0,00030,01130,0023Berilio Disuelto (Be)12671mg/L---0,00002<0,00002<0,00002Bismuto Disuelto (Bi)12671mg/L---0,00002<0,00002<0,00002Boro Disuelto (B)12671mg/L---0,0020,2040,310Cadmio Disuelto (Cd)12671mg/L---0,00002<0,00002<0,00002Calcio Disuelto (Ca)12671mg/L---0,0622,699,80Cromo Disuelto (Cr)12671mg/L---0,0001<0,0001<0,0001Cobalto Disuelto (Co)12671mg/L---0,0001<0,00010,0010Cobre Disuelto (Cu)12671mg/L---0,00050,00080,0016Hierro Disuelto (Fe)12671mg/L---0,006<0,0060,022Plomo Disuelto (Pb)12671mg/L---0,0004<0,0004<0,0004Litio Disuelto (Li)12671mg/L---0,00030,06700,0889Magnesio Disuelto (Mg)12671mg/L---0,00510,0204,014Manganeso Disuelto (Mn)12671mg/L---0,00010,00070,0031Mercurio Disuelto (Hg)12671mg/L---0,0001<0,0001<0,0001Molibdeno Disuelto (Mo)12671mg/L---0,00020,00190,0013Niquel Disuelto (Ni)12671mg/L---0,0001<0,0001<0,0001Fosforo Disuelto (P)12671mg/L---0,0050,0420,034Potasio Disuelto (K)12671mg/L---0,0095,3902,780Selenio Disuelto (Se)12671mg/L---0,0003<0,0003<0,0003Silicio Disuelto (Si)12671mg/L---0,0332,1021,90Plata Disuelta (Ag)12671mg/L---0,00002<0,00002<0,00002Sodio Disuelto (Na)12671mg/L---0,0121,3118,07Estroncio Disuelto (Sr)12671mg/L---0,00060,11200,0563Talio Disuelto (Tl)12671mg/L---0,0002<0,0002<0,0002Estaño Disuelto (Sn)12671mg/L---0,0005<0,0005<0,0005Titanio Disuelto (Ti)12671mg/L---0,0002<0,0002<0,0002Uranio Disuelto (U)12671mg/L---0,000060,006580,00272Vanadio Disuelto (V)12671mg/L---0,00030,02160,0187Zinc Disuelto (Zn)12671mg/L---0,00070,0114<0,0007Fecha de Análisis12671---------06/01/2017 00:0006/01/2017 00:00Oxígeno Disuelto14493mg/L0,10---6,566,92Fecha de Análisis14493---------26/12/2016 00:0026/12/2016 00:00Pág. 2 de 5 Hermanos Carrera Pinto #159, Parque Industrial Los Libertadores, Colina, Santiago, Chile | Telf +56 2 2654 6104
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INFORME DE ENSAYO: 48774/2016 Muestras del Item: 1N° ALS483362/2016-1.0483364/2016-1.0Fecha de Muestreo22/12/201621/12/2016Hora de Muestreo13:40:0017:45:00Tipo de MuestraAguaSuperficialAguaSuperficialIdentificaciónSI2B-IRIOParámetroCMUnidadLDLQValoresValorespH14524---0,01---7,478,09T° de pH14524°C------24,925,0Fecha de Análisis14524---------26/12/2016 16:0026/12/2016 16:00Alcalinidad Bicarbonato14526mg CaCO3/L1,0---149,076,9Fecha de Análisis14526---------05/01/2017 00:0005/01/2017 00:00Alcalinidad Carbonato14527mg CaCO3/L1,0---<1,0<1,0Fecha de Análisis14527---------05/01/2017 00:0005/01/2017 00:00Filtración de Metales Disueltos (Agua)15779---------sisiFecha de Análisis15779---------26/12/2016 15:1026/12/2016 15:10Amoniaco (NH3)17139mg/L0,01---0,010,01Fecha de Análisis17139---------04/01/2017 00:0004/01/2017 00:00 Muestras del Item: 2N° ALS483369/2016-1.0Fecha de Muestreo22/12/2016Hora de Muestreo11:00:00Tipo de MuestraAguaSubterráneaIdentificaciónSI2-IIParámetroCMUnidadLDLQValoresF, Fluoruro11551mg/L0,020,060,12Cl, Cloruro11551mg/L0,030,084,65ClO3, Clorato11551mg/L0,050,11<0,11Br, Bromuro11551mg/L0,050,10<0,10SO4, Sulfato11551mg/L0,160,1211,33N-NO2, Nitrito11551mg/L0,040,09<0,09N-NO3, Nitrato11551mg/L0,020,050,31P-PO4, Fosfato11551mg/L0,040,13<0,13Fecha de Análisis11551---------27/12/2016 10:00Conductividad Eléctrica11863μS/cm2,0---327,0Fecha de Análisis11863---------28/12/2016 00:00Aluminio Disuelto (Al)12671mg/L---0,01<0,01Antimonio Disuelto (Sb)12671mg/L---0,00020,0004Arsénico Disuelto (As)12671mg/L---0,00030,0524Bario Disuelto (Ba)12671mg/L---0,00030,0113Berilio Disuelto (Be)12671mg/L---0,00002<0,00002Bismuto Disuelto (Bi)12671mg/L---0,00002<0,00002Boro Disuelto (B)12671mg/L---0,0020,196Cadmio Disuelto (Cd)12671mg/L---0,00002<0,00002Calcio Disuelto (Ca)12671mg/L---0,0622,99Cromo Disuelto (Cr)12671mg/L---0,0001<0,0001Cobalto Disuelto (Co)12671mg/L---0,0001<0,0001Cobre Disuelto (Cu)12671mg/L---0,00050,0011Hierro Disuelto (Fe)12671mg/L---0,0060,031Plomo Disuelto (Pb)12671mg/L---0,0004<0,0004Litio Disuelto (Li)12671mg/L---0,00030,0660Magnesio Disuelto (Mg)12671mg/L---0,00510,440Manganeso Disuelto (Mn)12671mg/L---0,00010,0034Mercurio Disuelto (Hg)12671mg/L---0,0001<0,0001Pág. 3 de 5 Hermanos Carrera Pinto #159, Parque Industrial Los Libertadores, Colina, Santiago, Chile | Telf +56 2 2654 6104
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INFORME DE ENSAYO: 48774/2016 Muestras del Item: 2N° ALS483369/2016-1.0Fecha de Muestreo22/12/2016Hora de Muestreo11:00:00Tipo de MuestraAguaSubterráneaIdentificaciónSI2-IIParámetroCMUnidadLDLQValoresMolibdeno Disuelto (Mo)12671mg/L---0,00020,0019Niquel Disuelto (Ni)12671mg/L---0,0001<0,0001Fosforo Disuelto (P)12671mg/L---0,0050,042Potasio Disuelto (K)12671mg/L---0,0095,550Selenio Disuelto (Se)12671mg/L---0,0003<0,0003Silicio Disuelto (Si)12671mg/L---0,0332,20Plata Disuelta (Ag)12671mg/L---0,00002<0,00002Sodio Disuelto (Na)12671mg/L---0,0121,73Estroncio Disuelto (Sr)12671mg/L---0,00060,1122Talio Disuelto (Tl)12671mg/L---0,0002<0,0002Estaño Disuelto (Sn)12671mg/L---0,0005<0,0005Titanio Disuelto (Ti)12671mg/L---0,0002<0,0002Uranio Disuelto (U)12671mg/L---0,000060,00669Vanadio Disuelto (V)12671mg/L---0,00030,0210Zinc Disuelto (Zn)12671mg/L---0,0007<0,0007Fecha de Análisis12671---------06/01/2017 00:00Oxígeno Disuelto14493mg/L0,10---6,34Fecha de Análisis14493---------26/12/2016 00:00pH14524---0,01---7,46T° de pH14524°C------25,1Fecha de Análisis14524---------26/12/2016 16:00Alcalinidad Bicarbonato14526mg CaCO3/L1,0---153,7Fecha de Análisis14526---------05/01/2017 00:00Alcalinidad Carbonato14527mg CaCO3/L1,0---<1,0Fecha de Análisis14527---------05/01/2017 00:00Filtración de Metales Disueltos (Agua)15779---------siFecha de Análisis15779---------26/12/2016 15:10Amoniaco (NH3)17139mg/L0,01---0,01Fecha de Análisis17139---------04/01/2017 00:00Pág. 4 de 5 Hermanos Carrera Pinto #159, Parque Industrial Los Libertadores, Colina, Santiago, Chile | Telf +56 2 2654 6104
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INFORME DE ENSAYO: 48774/2016REFERENCIAS DE LOS MÉTODOS DE ENSAYO(*)Parámetros fuera del alcance de acreditación.CMSedeParámetroMétodo de ReferenciaLaboratorio11551SCL Aniones por Cromatografía Iónica(Aguas)US EPA 300.1. 3ed.4ta act 2011.SCL - Inorganico12671SCL Metales Disueltos ICP-MS (Agua)EPA METHOD 6020 A -INDUCTIVELY COUPLEDPLASMA – MASSSPECTROMETRYSCL - Metales14493ANT(*) Oxígeno Disuelto (SM)SM 4500-O-G. Ed 22, 2012.ANT - Inorganico14526ANTAlcalinidad BicarbonatoQWI-IO-ALC-01, Emisión C, mod. 1SM 2320 B, 22nd Edition 2012ANT - Inorganico14527ANTAlcalinidad Carbonato (SM)QWI-IO-ALC-01, Emisión C, mod. 1SM 2320 B, 22nd Edition 2012ANT - Inorganico11863ANTConductividad Eléctrica (SM)QWI-IO-COND-01, Emisión B,mod.4SM 2510 B, 22nd Edition 2012ANT - Inorganico15779ANTFiltración de Metales Disueltos(Agua)SM 3030-B, 21 st ed. 2005ANT - Preparación de muestras17139ANTNH3 Amonio (SM), SubcontratadoETFASM 4500 NH3 DANT - Subcontratado14524ANTpH, Agua (SM)SM 4500-H+ B, 22nd Edition 2012ANT - InorganicoCOMENTARIOSLD = Límite de detecciónLQ = Límite de cuantificaciónLos Límites de Detección y/o Cuantificación para muestras de agua que son indicados en el presente documento, fueron determinadosexperimentalmente en matriz de “Agua Potable”, cabe indicar, que Límites pueden variar dependiendo de la Interferencias propias de cadaMatriz.CM = Código interno del Método de Análisis de ALS Life Sciences Chile S.A.ANT: Juan Gutemberg 438 Galpón 9, Antofagasta, Chile.SCL: Avda. Hermanos Carreras Pinto N°159 Parque Industrial Los Libertadores Colina - Santiago de Chile."EPA": U.S. Environmental Protection Agency."SM": Standard Methods for the Examination of Water and Wastewater."Nch": Norma Chilena."QWI": Procedimiento interno.El presente documento es redactado íntegramente en ALS Life Sciences Chile S.A., su alteración o su uso indebido constituye delito contra lafe pública y se regula por las disposiciones civiles y penales de la materia, queda prohibida la reproducción parcial del presente informe, salvoautorización escrita de ALS Life Sciences Chile S.A.; sólo es válido para las muestras referidas en el presente informe.Las muestras de agua se descartaran 30 días calendarios desde la fecha de emisión del informe de resultados, para el caso de las suelos osedimentos se considerarán 90 días calendario.El presente informe corresponde a 3 muestra(s).El responsable del muestreo es: Cliente quien se responsabiliza por su correcta identificación y preservaciónMuestra(s) recibida(s) en buenas condiciones, en el tipo de recipiente adecuado y a 5 °CLos resultados contenidos en este Informe de ensayo sólo son válidos para las muestras analizadas.FIN DEL REPORTEPág. 5 de 5 Hermanos Carrera Pinto #159, Parque Industrial Los Libertadores, Colina, Santiago, Chile | Telf +56 2 2654 6104
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INFORME DE ENSAYO: 48767/2016Propuesta comercial: 15818/2016.3Arcadis Chile SPAAntonio Varas 621 - Providencia - SantiagoAtención: Ximena OrregoAnálisis Terreno SilalaMuestras recibidas el: 26/12/2016Informe generado el 12/01/2017Pág. 1 de 6 Hermanos Carrera Pinto #159, Parque Industrial Los Libertadores, Colina, Santiago, Chile | Telf +56 2 2654 6104
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INFORME DE ENSAYO: 48767/2016RESULTADOS ANALÍTICOS Muestras del Item: 2N° ALS483187/2016-1.0483188/2016-1.0483192/2016-1.0Fecha de Muestreo20/12/201620/12/201621/12/2016Hora de Muestreo15:20:0016:00:0012:12:00Tipo de MuestraAguaSubterráneaAguaSubterráneaAguaSubterráneaIdentificaciónSI-02SI-01SI-21ParámetroCMUnidadLDLQValoresValoresValoresF, Fluoruro11551mg/L0,020,060,090,091,08Cl, Cloruro11551mg/L0,030,082,342,1370,33ClO3, Clorato11551mg/L0,050,11<0,11<0,11<0,11Br, Bromuro11551mg/L0,050,10<0,10<0,10<0,10SO4, Sulfato11551mg/L0,160,125,926,1187,58N-NO2, Nitrito11551mg/L0,040,09<0,09<0,09<0,09N-NO3, Nitrato11551mg/L0,020,050,190,330,21P-PO4, Fosfato11551mg/L0,040,13<0,13<0,13<0,13Fecha de Análisis11551---------27/12/2016 10:0027/12/2016 10:0027/12/2016 10:00Conductividad Eléctrica11863μS/cm2,0---204,8189,7617,0Fecha de Análisis11863---------28/12/2016 00:0028/12/2016 00:0028/12/2016 00:00Aluminio Disuelto (Al)12671mg/L---0,010,01<0,010,01Antimonio Disuelto (Sb)12671mg/L---0,00020,00110,00100,0176Arsénico Disuelto (As)12671mg/L---0,00030,11500,08950,7786Bario Disuelto (Ba)12671mg/L---0,00030,00150,00300,0085Berilio Disuelto (Be)12671mg/L---0,00002<0,00002<0,00002<0,00002Bismuto Disuelto (Bi)12671mg/L---0,00002<0,00002<0,00002<0,00002Boro Disuelto (B)12671mg/L---0,0020,2380,2091,422Cadmio Disuelto (Cd)12671mg/L---0,00002<0,00002<0,00002<0,00002Calcio Disuelto (Ca)12671mg/L---0,069,9010,3423,31Cromo Disuelto (Cr)12671mg/L---0,0001<0,00010,0007<0,0001Cobalto Disuelto (Co)12671mg/L---0,00010,0005<0,00010,0005Cobre Disuelto (Cu)12671mg/L---0,00050,0009<0,00050,0010Hierro Disuelto (Fe)12671mg/L---0,0060,0290,015<0,006Plomo Disuelto (Pb)12671mg/L---0,0004<0,0004<0,0004<0,0004Litio Disuelto (Li)12671mg/L---0,00030,09770,06580,3547Magnesio Disuelto (Mg)12671mg/L---0,0054,0994,2939,187Manganeso Disuelto (Mn)12671mg/L---0,00010,0019<0,00010,0017Mercurio Disuelto (Hg)12671mg/L---0,0001<0,0001<0,0001<0,0001Molibdeno Disuelto (Mo)12671mg/L---0,00020,00120,00130,0045Niquel Disuelto (Ni)12671mg/L---0,0001<0,0001<0,0001<0,0001Fosforo Disuelto (P)12671mg/L---0,0050,0220,0340,065Potasio Disuelto (K)12671mg/L---0,0092,5002,9609,930Selenio Disuelto (Se)12671mg/L---0,0003<0,0003<0,0003<0,0003Silicio Disuelto (Si)12671mg/L---0,0318,8022,0036,60Plata Disuelta (Ag)12671mg/L---0,00002<0,00002<0,00002<0,00002Sodio Disuelto (Na)12671mg/L---0,0119,7416,7566,67Estroncio Disuelto (Sr)12671mg/L---0,00060,05740,05870,2974Talio Disuelto (Tl)12671mg/L---0,0002<0,0002<0,0002<0,0002Estaño Disuelto (Sn)12671mg/L---0,0005<0,0005<0,0005<0,0005Titanio Disuelto (Ti)12671mg/L---0,0002<0,0002<0,0002<0,0002Uranio Disuelto (U)12671mg/L---0,000060,003360,002350,00040Vanadio Disuelto (V)12671mg/L---0,00030,01970,01810,0320Zinc Disuelto (Zn)12671mg/L---0,0007<0,0007<0,0007<0,0007Fecha de Análisis12671---------06/01/2017 00:0006/01/2017 00:0006/01/2017 00:00Oxígeno Disuelto14493mg/L0,10---6,937,756,24Fecha de Análisis14493---------26/12/2016 00:0026/12/2016 00:0026/12/2016 00:00Pág. 2 de 6 Hermanos Carrera Pinto #159, Parque Industrial Los Libertadores, Colina, Santiago, Chile | Telf +56 2 2654 6104
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INFORME DE ENSAYO: 48767/2016 Muestras del Item: 2N° ALS483187/2016-1.0483188/2016-1.0483192/2016-1.0Fecha de Muestreo20/12/201620/12/201621/12/2016Hora de Muestreo15:20:0016:00:0012:12:00Tipo de MuestraAguaSubterráneaAguaSubterráneaAguaSubterráneaIdentificaciónSI-02SI-01SI-21ParámetroCMUnidadLDLQValoresValoresValorespH14524---0,01---8,677,767,01T° de pH14524°C------25,125,024,9Fecha de Análisis14524---------26/12/2016 16:0026/12/2016 16:0026/12/2016 16:00Alcalinidad Bicarbonato14526mg CaCO3/L1,0---75,176,091,0Fecha de Análisis14526---------05/01/2017 00:0005/01/2017 00:0005/01/2017 00:00Alcalinidad Carbonato14527mg CaCO3/L1,0---<1,0<1,0<1,0Fecha de Análisis14527---------05/01/2017 00:0005/01/2017 00:0005/01/2017 00:00Filtración de Metales Disueltos (Agua)15779---------sisisiFecha de Análisis15779---------26/12/2016 10:3026/12/2016 10:3026/12/2016 10:30Amoniaco (NH3)17139mg/L0,01---0,010,010,041Fecha de Análisis17139---------04/01/2017 00:0004/01/2017 00:0007/01/2017 00:00 Muestras del Item: 2N° ALS483193/2016-1.0483229/2016-1.0Fecha de Muestreo21/12/201621/12/2016Hora de Muestreo15:15:0013:44:00Tipo de MuestraAguaSubterráneaAguaSubterráneaIdentificaciónSI-05SI-11ParámetroCMUnidadLDLQValoresValoresF, Fluoruro11551mg/L0,020,060,13---Cl, Cloruro11551mg/L0,030,081,28---ClO3, Clorato11551mg/L0,050,11<0,11---Br, Bromuro11551mg/L0,050,10<0,10---SO4, Sulfato11551mg/L0,160,128,26---N-NO2, Nitrito11551mg/L0,040,09<0,09---N-NO3, Nitrato11551mg/L0,020,050,27---P-PO4, Fosfato11551mg/L0,040,13<0,13---F, Fluoruro11551mg/L0,020,06---0,10Cl, Cloruro11551mg/L0,030,08---1,86ClO3, Clorato11551mg/L0,050,11---<0,11Br, Bromuro11551mg/L0,050,10---<0,10SO4, Sulfato11551mg/L0,160,12---9,80N-NO2, Nitrito11551mg/L0,040,09---<0,09N-NO3, Nitrato11551mg/L0,020,05---0,32P-PO4, Fosfato11551mg/L0,040,13---<0,13Fecha de Análisis11551---------27/12/2016 10:0027/12/2016 10:00Conductividad Eléctrica11863μS/cm2,0---88,3---Conductividad Eléctrica11863μS/cm2,0------315,0Fecha de Análisis11863---------28/12/2016 00:0028/12/2016 00:00Aluminio Disuelto (Al)12671mg/L---0,010,02---Antimonio Disuelto (Sb)12671mg/L---0,00020,0003---Arsénico Disuelto (As)12671mg/L---0,00030,0110---Bario Disuelto (Ba)12671mg/L---0,00030,0039---Berilio Disuelto (Be)12671mg/L---0,00002<0,00002---Bismuto Disuelto (Bi)12671mg/L---0,00002<0,00002---Boro Disuelto (B)12671mg/L---0,0020,125---Cadmio Disuelto (Cd)12671mg/L---0,00002<0,00002---Calcio Disuelto (Ca)12671mg/L---0,063,93---Cromo Disuelto (Cr)12671mg/L---0,0001<0,0001---Cobalto Disuelto (Co)12671mg/L---0,0001<0,0001---Pág. 3 de 6 Hermanos Carrera Pinto #159, Parque Industrial Los Libertadores, Colina, Santiago, Chile | Telf +56 2 2654 6104
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INFORME DE ENSAYO: 48767/2016 Muestras del Item: 2N° ALS483193/2016-1.0483229/2016-1.0Fecha de Muestreo21/12/201621/12/2016Hora de Muestreo15:15:0013:44:00Tipo de MuestraAguaSubterráneaAguaSubterráneaIdentificaciónSI-05SI-11ParámetroCMUnidadLDLQValoresValoresCobre Disuelto (Cu)12671mg/L---0,0005<0,0005---Hierro Disuelto (Fe)12671mg/L---0,0060,019---Plomo Disuelto (Pb)12671mg/L---0,0004<0,0004---Litio Disuelto (Li)12671mg/L---0,00030,0162---Magnesio Disuelto (Mg)12671mg/L---0,0050,646---Manganeso Disuelto (Mn)12671mg/L---0,0001<0,0001---Mercurio Disuelto (Hg)12671mg/L---0,0001<0,0001---Molibdeno Disuelto (Mo)12671mg/L---0,00020,0010---Niquel Disuelto (Ni)12671mg/L---0,0001<0,0001---Fosforo Disuelto (P)12671mg/L---0,0050,025---Potasio Disuelto (K)12671mg/L---0,0092,910---Selenio Disuelto (Se)12671mg/L---0,0003<0,0003---Silicio Disuelto (Si)12671mg/L---0,0321,40---Plata Disuelta (Ag)12671mg/L---0,00002<0,00002---Sodio Disuelto (Na)12671mg/L---0,0110,37---Estroncio Disuelto (Sr)12671mg/L---0,00060,0169---Talio Disuelto (Tl)12671mg/L---0,0002<0,0002---Estaño Disuelto (Sn)12671mg/L---0,0005<0,0005---Titanio Disuelto (Ti)12671mg/L---0,00020,0027---Uranio Disuelto (U)12671mg/L---0,00006<0,00006---Vanadio Disuelto (V)12671mg/L---0,00030,0210---Zinc Disuelto (Zn)12671mg/L---0,0007<0,0007---Aluminio Disuelto (Al)12671mg/L---0,01---<0,01Antimonio Disuelto (Sb)12671mg/L---0,0002---0,0006Arsénico Disuelto (As)12671mg/L---0,0003---0,0555Bario Disuelto (Ba)12671mg/L---0,0003---0,0141Berilio Disuelto (Be)12671mg/L---0,00002---<0,00002Bismuto Disuelto (Bi)12671mg/L---0,00002---<0,00002Boro Disuelto (B)12671mg/L---0,002---0,201Cadmio Disuelto (Cd)12671mg/L---0,00002---<0,00002Calcio Disuelto (Ca)12671mg/L---0,06---21,89Cromo Disuelto (Cr)12671mg/L---0,0001---<0,0001Cobalto Disuelto (Co)12671mg/L---0,0001---0,0011Cobre Disuelto (Cu)12671mg/L---0,0005---0,0009Hierro Disuelto (Fe)12671mg/L---0,006---<0,006Plomo Disuelto (Pb)12671mg/L---0,0004---<0,0004Litio Disuelto (Li)12671mg/L---0,0003---0,0671Magnesio Disuelto (Mg)12671mg/L---0,005---10,300Manganeso Disuelto (Mn)12671mg/L---0,0001---0,0020Mercurio Disuelto (Hg)12671mg/L---0,0001---<0,0001Molibdeno Disuelto (Mo)12671mg/L---0,0002---0,0018Niquel Disuelto (Ni)12671mg/L---0,0001---<0,0001Fosforo Disuelto (P)12671mg/L---0,005---0,042Potasio Disuelto (K)12671mg/L---0,009---5,070Selenio Disuelto (Se)12671mg/L---0,0003---<0,0003Silicio Disuelto (Si)12671mg/L---0,03---30,70Plata Disuelta (Ag)12671mg/L---0,00002---<0,00002Sodio Disuelto (Na)12671mg/L---0,01---21,09Estroncio Disuelto (Sr)12671mg/L---0,0006---0,1134Talio Disuelto (Tl)12671mg/L---0,0002---<0,0002Estaño Disuelto (Sn)12671mg/L---0,0005---<0,0005Pág. 4 de 6 Hermanos Carrera Pinto #159, Parque Industrial Los Libertadores, Colina, Santiago, Chile | Telf +56 2 2654 6104
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INFORME DE ENSAYO: 48767/2016 Muestras del Item: 2N° ALS483193/2016-1.0483229/2016-1.0Fecha de Muestreo21/12/201621/12/2016Hora de Muestreo15:15:0013:44:00Tipo de MuestraAguaSubterráneaAguaSubterráneaIdentificaciónSI-05SI-11ParámetroCMUnidadLDLQValoresValoresTitanio Disuelto (Ti)12671mg/L---0,0002---<0,0002Uranio Disuelto (U)12671mg/L---0,00006---0,00654Vanadio Disuelto (V)12671mg/L---0,0003---0,0205Zinc Disuelto (Zn)12671mg/L---0,0007---<0,0007Fecha de Análisis12671---------06/01/2017 00:0006/01/2017 00:00Oxígeno Disuelto14493mg/L0,10---6,75---Oxígeno Disuelto14493mg/L0,10------6,84Fecha de Análisis14493---------26/12/2016 00:0026/12/2016 00:00pH14524---0,01---7,58---T° de pH14524°C------25,0---pH14524---0,01------7,80T° de pH14524°C---------25,1Fecha de Análisis14524---------26/12/2016 16:0026/12/2016 16:00Alcalinidad Bicarbonato14526mg CaCO3/L1,0---24,9---Alcalinidad Bicarbonato14526mg CaCO3/L1,0------139,6Fecha de Análisis14526---------05/01/2017 00:0005/01/2017 00:00Alcalinidad Carbonato14527mg CaCO3/L1,0---<1,0---Alcalinidad Carbonato14527mg CaCO3/L1,0------<1,0Fecha de Análisis14527---------05/01/2017 00:0005/01/2017 00:00Filtración de Metales Disueltos (Agua)15779---------si---Filtración de Metales Disueltos (Agua)15779------------siFecha de Análisis15779---------26/12/2016 10:3026/12/2016 15:10Amoniaco (NH3)17139mg/L0,01---0,01---Amoniaco (NH3)17139mg/L0,01------0,01Fecha de Análisis17139---------04/01/2017 00:0004/01/2017 00:00Pág. 5 de 6 Hermanos Carrera Pinto #159, Parque Industrial Los Libertadores, Colina, Santiago, Chile | Telf +56 2 2654 6104
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INFORME DE ENSAYO: 48767/2016REFERENCIAS DE LOS MÉTODOS DE ENSAYO(*)Parámetros fuera del alcance de acreditación.CMSedeParámetroMétodo de ReferenciaLaboratorio11551SCL Aniones por Cromatografía Iónica(Aguas)US EPA 300.1. 3ed.4ta act 2011.SCL - Inorganico12671SCL Metales Disueltos ICP-MS (Agua)EPA METHOD 6020 A -INDUCTIVELY COUPLEDPLASMA – MASSSPECTROMETRYSCL - Metales14493ANT(*) Oxígeno Disuelto (SM)SM 4500-O-G. Ed 22, 2012.ANT - Inorganico14526ANTAlcalinidad BicarbonatoQWI-IO-ALC-01, Emisión C, mod. 1SM 2320 B, 22nd Edition 2012ANT - Inorganico14527ANTAlcalinidad Carbonato (SM)QWI-IO-ALC-01, Emisión C, mod. 1SM 2320 B, 22nd Edition 2012ANT - Inorganico11863ANTConductividad Eléctrica (SM)QWI-IO-COND-01, Emisión B,mod.4SM 2510 B, 22nd Edition 2012ANT - Inorganico15779ANTFiltración de Metales Disueltos(Agua)SM 3030-B, 21 st ed. 2005ANT - Preparación de muestras17139ANTNH3 Amonio (SM), SubcontratadoETFASM 4500 NH3 DANT - Subcontratado14524ANTpH, Agua (SM)SM 4500-H+ B, 22nd Edition 2012ANT - InorganicoCOMENTARIOSLD = Límite de detecciónLQ = Límite de cuantificaciónLos Límites de Detección y/o Cuantificación para muestras de agua que son indicados en el presente documento, fueron determinadosexperimentalmente en matriz de “Agua Potable”, cabe indicar, que Límites pueden variar dependiendo de la Interferencias propias de cadaMatriz.CM = Código interno del Método de Análisis de ALS Life Sciences Chile S.A.ANT: Juan Gutemberg 438 Galpón 9, Antofagasta, Chile.SCL: Avda. Hermanos Carreras Pinto N°159 Parque Industrial Los Libertadores Colina - Santiago de Chile."EPA": U.S. Environmental Protection Agency."SM": Standard Methods for the Examination of Water and Wastewater."Nch": Norma Chilena."QWI": Procedimiento interno.El presente documento es redactado íntegramente en ALS Life Sciences Chile S.A., su alteración o su uso indebido constituye delito contra lafe pública y se regula por las disposiciones civiles y penales de la materia, queda prohibida la reproducción parcial del presente informe, salvoautorización escrita de ALS Life Sciences Chile S.A.; sólo es válido para las muestras referidas en el presente informe.Las muestras de agua se descartaran 30 días calendarios desde la fecha de emisión del informe de resultados, para el caso de las suelos osedimentos se considerarán 90 días calendario.El presente informe corresponde a 5 muestra(s).El responsable del muestreo es: Cliente quien se responsabiliza por su correcta identificación y preservaciónMuestra(s) recibida(s) en buenas condiciones, en el tipo de recipiente adecuado y a 5 °CLos resultados contenidos en este Informe de ensayo sólo son válidos para las muestras analizadas.FIN DEL REPORTEPág. 6 de 6 Hermanos Carrera Pinto #159, Parque Industrial Los Libertadores, Colina, Santiago, Chile | Telf +56 2 2654 6104
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INFORME DE ENSAYO: 48781/2016Propuesta comercial: 15818/2016.3Arcadis Chile SPAAntonio Varas 621 - Providencia - SantiagoAtención: Ximena OrregoAnálisis Terreno SilalaMuestras recibidas el: 26/12/2016Informe generado el 12/01/2017Pág. 1 de 5 Hermanos Carrera Pinto #159, Parque Industrial Los Libertadores, Colina, Santiago, Chile | Telf +56 2 2654 6104
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INFORME DE ENSAYO: 48781/2016RESULTADOS ANALÍTICOS Muestras del Item: 1N° ALS483403/2016-1.0483404/2016-1.0483405/2016-1.0Fecha de Muestreo21/12/201622/12/201621/12/2016Hora de Muestreo16:25:0019:20:0019:25:00Tipo de MuestraAguaSuperficialAguaSuperficialAguaSuperficialIdentificaciónSI4-BSilala 1ASI2-IParámetroCMUnidadLDLQValoresValoresValoresF, Fluoruro11551mg/L0,020,060,070,110,11Cl, Cloruro11551mg/L0,030,086,482,582,19ClO3, Clorato11551mg/L0,050,11<0,11<0,11<0,11Br, Bromuro11551mg/L0,050,10<0,10<0,10<0,10SO4, Sulfato11551mg/L0,160,1217,1311,7310,35N-NO2, Nitrito11551mg/L0,040,09<0,09<0,09<0,09N-NO3, Nitrato11551mg/L0,020,050,560,290,28P-PO4, Fosfato11551mg/L0,040,13<0,13<0,13<0,13Fecha de Análisis11551---------27/12/2016 10:0027/12/2016 10:0027/12/2016 10:00Conductividad Eléctrica11863μS/cm2,0---345,0288,3321,0Fecha de Análisis11863---------28/12/2016 00:0028/12/2016 00:0028/12/2016 00:00Aluminio Disuelto (Al)12671mg/L---0,010,020,020,04Antimonio Disuelto (Sb)12671mg/L---0,00020,00060,00040,0004Arsénico Disuelto (As)12671mg/L---0,00030,07390,05860,0536Bario Disuelto (Ba)12671mg/L---0,00030,00610,00820,0106Berilio Disuelto (Be)12671mg/L---0,00002<0,00002<0,00002<0,00002Bismuto Disuelto (Bi)12671mg/L---0,00002<0,00002<0,00002<0,00002Boro Disuelto (B)12671mg/L---0,0020,2160,1930,205Cadmio Disuelto (Cd)12671mg/L---0,00002<0,00002<0,00002<0,00002Calcio Disuelto (Ca)12671mg/L---0,0622,0920,9323,11Cromo Disuelto (Cr)12671mg/L---0,00010,0056<0,0001<0,0001Cobalto Disuelto (Co)12671mg/L---0,0001<0,0001<0,0001<0,0001Cobre Disuelto (Cu)12671mg/L---0,00050,00300,00170,0015Hierro Disuelto (Fe)12671mg/L---0,0060,0290,0200,036Plomo Disuelto (Pb)12671mg/L---0,00040,0008<0,0004<0,0004Litio Disuelto (Li)12671mg/L---0,00030,08680,06580,0679Magnesio Disuelto (Mg)12671mg/L---0,00511,6609,24310,470Manganeso Disuelto (Mn)12671mg/L---0,00010,00500,00130,0044Mercurio Disuelto (Hg)12671mg/L---0,0001<0,0001<0,0001<0,0001Molibdeno Disuelto (Mo)12671mg/L---0,00020,00210,00190,0018Niquel Disuelto (Ni)12671mg/L---0,00010,0022<0,0001<0,0001Fosforo Disuelto (P)12671mg/L---0,0050,0360,0430,038Potasio Disuelto (K)12671mg/L---0,0094,8105,2205,610Selenio Disuelto (Se)12671mg/L---0,0003<0,0003<0,0003<0,0003Silicio Disuelto (Si)12671mg/L---0,0329,1028,5032,80Plata Disuelta (Ag)12671mg/L---0,00002<0,00002<0,00002<0,00002Sodio Disuelto (Na)12671mg/L---0,0126,5122,0621,97Estroncio Disuelto (Sr)12671mg/L---0,00060,11530,10370,1129Talio Disuelto (Tl)12671mg/L---0,0002<0,0002<0,0002<0,0002Estaño Disuelto (Sn)12671mg/L---0,00050,0014<0,0005<0,0005Titanio Disuelto (Ti)12671mg/L---0,00020,0012<0,0002<0,0002Uranio Disuelto (U)12671mg/L---0,000060,005310,004670,00643Vanadio Disuelto (V)12671mg/L---0,00030,01640,02270,0212Zinc Disuelto (Zn)12671mg/L---0,00070,0147<0,0007<0,0007Fecha de Análisis12671---------06/01/2017 00:0006/01/2017 00:0006/01/2017 00:00Oxígeno Disuelto14493mg/L0,10---5,906,516,39Fecha de Análisis14493---------26/12/2016 00:0026/12/2016 00:0026/12/2016 00:00Pág. 2 de 5 Hermanos Carrera Pinto #159, Parque Industrial Los Libertadores, Colina, Santiago, Chile | Telf +56 2 2654 6104
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Annex III Appendix E
INFORME DE ENSAYO: 48781/2016 Muestras del Item: 1N° ALS483403/2016-1.0483404/2016-1.0483405/2016-1.0Fecha de Muestreo21/12/201622/12/201621/12/2016Hora de Muestreo16:25:0019:20:0019:25:00Tipo de MuestraAguaSuperficialAguaSuperficialAguaSuperficialIdentificaciónSI4-BSilala 1ASI2-IParámetroCMUnidadLDLQValoresValoresValorespH14524---0,01---7,487,597,56T° de pH14524°C------25,125,024,9Fecha de Análisis14524---------26/12/2016 16:0026/12/2016 16:0026/12/2016 16:00Alcalinidad Bicarbonato14526mg CaCO3/L1,0---146,9137,0150,7Fecha de Análisis14526---------05/01/2017 00:0005/01/2017 00:0005/01/2017 00:00Alcalinidad Carbonato14527mg CaCO3/L1,0---<1,0<1,0<1,0Fecha de Análisis14527---------05/01/2017 00:0005/01/2017 00:0005/01/2017 00:00Filtración de Metales Disueltos (Agua)15779---------sisisiFecha de Análisis15779---------26/12/2016 15:1026/12/2016 15:1026/12/2016 15:10Amoniaco (NH3)17139mg/L0,01---0,0280,0310,033Fecha de Análisis17139---------07/01/2017 00:0007/01/2017 00:0007/01/2017 00:00 Muestras del Item: 1N° ALS483406/2016-1.0483407/2016-1.0Fecha de Muestreo21/12/201621/12/2016Hora de Muestreo15:55:0015:30:00Tipo de MuestraAguaSuperficialAguaSuperficialIdentificaciónSI4-ASI1-BParámetroCMUnidadLDLQValoresValoresF, Fluoruro11551mg/L0,020,060,070,09Cl, Cloruro11551mg/L0,030,087,295,36ClO3, Clorato11551mg/L0,050,11<0,11<0,11Br, Bromuro11551mg/L0,050,10<0,10<0,10SO4, Sulfato11551mg/L0,160,1213,6911,03N-NO2, Nitrito11551mg/L0,040,09<0,09<0,09N-NO3, Nitrato11551mg/L0,020,050,580,30P-PO4, Fosfato11551mg/L0,040,13<0,13<0,13Fecha de Análisis11551---------27/12/2016 10:0027/12/2016 10:00Conductividad Eléctrica11863μS/cm2,0---356,0354,0Fecha de Análisis11863---------28/12/2016 00:0028/12/2016 00:00Aluminio Disuelto (Al)12671mg/L---0,010,01<0,01Antimonio Disuelto (Sb)12671mg/L---0,00020,00050,0004Arsénico Disuelto (As)12671mg/L---0,00030,07340,0601Bario Disuelto (Ba)12671mg/L---0,00030,00670,0047Berilio Disuelto (Be)12671mg/L---0,00002<0,00002<0,00002Bismuto Disuelto (Bi)12671mg/L---0,00002<0,00002<0,00002Boro Disuelto (B)12671mg/L---0,0020,2130,212Cadmio Disuelto (Cd)12671mg/L---0,00002<0,00002<0,00002Calcio Disuelto (Ca)12671mg/L---0,0621,5724,90Cromo Disuelto (Cr)12671mg/L---0,00010,0015<0,0001Cobalto Disuelto (Co)12671mg/L---0,0001<0,0001<0,0001Cobre Disuelto (Cu)12671mg/L---0,00050,0042<0,0005Hierro Disuelto (Fe)12671mg/L---0,0060,0230,065Plomo Disuelto (Pb)12671mg/L---0,00040,0006<0,0004Litio Disuelto (Li)12671mg/L---0,00030,08560,0856Magnesio Disuelto (Mg)12671mg/L---0,00511,89012,700Manganeso Disuelto (Mn)12671mg/L---0,00010,00420,0100Mercurio Disuelto (Hg)12671mg/L---0,0001<0,0001<0,0001Molibdeno Disuelto (Mo)12671mg/L---0,00020,00210,0019Niquel Disuelto (Ni)12671mg/L---0,00010,0036<0,0001Pág. 3 de 5 Hermanos Carrera Pinto #159, Parque Industrial Los Libertadores, Colina, Santiago, Chile | Telf +56 2 2654 6104
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INFORME DE ENSAYO: 48781/2016 Muestras del Item: 1N° ALS483406/2016-1.0483407/2016-1.0Fecha de Muestreo21/12/201621/12/2016Hora de Muestreo15:55:0015:30:00Tipo de MuestraAguaSuperficialAguaSuperficialIdentificaciónSI4-ASI1-BParámetroCMUnidadLDLQValoresValoresFosforo Disuelto (P)12671mg/L---0,0050,0590,041Potasio Disuelto (K)12671mg/L---0,0094,9004,990Selenio Disuelto (Se)12671mg/L---0,0003<0,0003<0,0003Silicio Disuelto (Si)12671mg/L---0,0329,6028,00Plata Disuelta (Ag)12671mg/L---0,00002<0,00002<0,00002Sodio Disuelto (Na)12671mg/L---0,0126,1224,79Estroncio Disuelto (Sr)12671mg/L---0,00060,11610,1302Talio Disuelto (Tl)12671mg/L---0,0002<0,0002<0,0002Estaño Disuelto (Sn)12671mg/L---0,00050,0010<0,0005Titanio Disuelto (Ti)12671mg/L---0,0002<0,0002<0,0002Uranio Disuelto (U)12671mg/L---0,000060,005360,00753Vanadio Disuelto (V)12671mg/L---0,00030,01610,0171Zinc Disuelto (Zn)12671mg/L---0,00070,0166<0,0007Fecha de Análisis12671---------06/01/2017 00:0006/01/2017 00:00Oxígeno Disuelto14493mg/L0,10---6,105,95Fecha de Análisis14493---------26/12/2016 00:0026/12/2016 00:00pH14524---0,01---7,497,53T° de pH14524°C------25,025,0Fecha de Análisis14524---------26/12/2016 16:0026/12/2016 16:00Alcalinidad Bicarbonato14526mg CaCO3/L1,0---149,0164,9Fecha de Análisis14526---------05/01/2017 00:0005/01/2017 00:00Alcalinidad Carbonato14527mg CaCO3/L1,0---<1,0<1,0Fecha de Análisis14527---------05/01/2017 00:0005/01/2017 00:00Filtración de Metales Disueltos (Agua)15779---------sisiFecha de Análisis15779---------26/12/2016 15:1026/12/2016 15:10Amoniaco (NH3)17139mg/L0,01---0,030,022Fecha de Análisis17139---------07/01/2017 00:0007/01/2017 00:00Pág. 4 de 5 Hermanos Carrera Pinto #159, Parque Industrial Los Libertadores, Colina, Santiago, Chile | Telf +56 2 2654 6104
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Annex III Appendix E
INFORME DE ENSAYO: 48781/2016REFERENCIAS DE LOS MÉTODOS DE ENSAYO(*)Parámetros fuera del alcance de acreditación.CMSedeParámetroMétodo de ReferenciaLaboratorio11551SCL Aniones por Cromatografía Iónica(Aguas)US EPA 300.1. 3ed.4ta act 2011.SCL - Inorganico12671SCL Metales Disueltos ICP-MS (Agua)EPA METHOD 6020 A -INDUCTIVELY COUPLEDPLASMA – MASSSPECTROMETRYSCL - Metales14493ANT(*) Oxígeno Disuelto (SM)SM 4500-O-G. Ed 22, 2012.ANT - Inorganico14526ANTAlcalinidad BicarbonatoQWI-IO-ALC-01, Emisión C, mod. 1SM 2320 B, 22nd Edition 2012ANT - Inorganico14527ANTAlcalinidad Carbonato (SM)QWI-IO-ALC-01, Emisión C, mod. 1SM 2320 B, 22nd Edition 2012ANT - Inorganico11863ANTConductividad Eléctrica (SM)QWI-IO-COND-01, Emisión B,mod.4SM 2510 B, 22nd Edition 2012ANT - Inorganico15779ANTFiltración de Metales Disueltos(Agua)SM 3030-B, 21 st ed. 2005ANT - Preparación de muestras17139ANTNH3 Amonio (SM), SubcontratadoETFASM 4500 NH3 DANT - Subcontratado14524ANTpH, Agua (SM)SM 4500-H+ B, 22nd Edition 2012ANT - InorganicoCOMENTARIOSLD = Límite de detecciónLQ = Límite de cuantificaciónLos Límites de Detección y/o Cuantificación para muestras de agua que son indicados en el presente documento, fueron determinadosexperimentalmente en matriz de “Agua Potable”, cabe indicar, que Límites pueden variar dependiendo de la Interferencias propias de cadaMatriz.CM = Código interno del Método de Análisis de ALS Life Sciences Chile S.A.ANT: Juan Gutemberg 438 Galpón 9, Antofagasta, Chile.SCL: Avda. Hermanos Carreras Pinto N°159 Parque Industrial Los Libertadores Colina - Santiago de Chile."EPA": U.S. Environmental Protection Agency."SM": Standard Methods for the Examination of Water and Wastewater."Nch": Norma Chilena."QWI": Procedimiento interno.El presente documento es redactado íntegramente en ALS Life Sciences Chile S.A., su alteración o su uso indebido constituye delito contra lafe pública y se regula por las disposiciones civiles y penales de la materia, queda prohibida la reproducción parcial del presente informe, salvoautorización escrita de ALS Life Sciences Chile S.A.; sólo es válido para las muestras referidas en el presente informe.Las muestras de agua se descartaran 30 días calendarios desde la fecha de emisión del informe de resultados, para el caso de las suelos osedimentos se considerarán 90 días calendario.El presente informe corresponde a 5 muestra(s).El responsable del muestreo es: Cliente quien se responsabiliza por su correcta identificación y preservaciónMuestra(s) recibida(s) en buenas condiciones, en el tipo de recipiente adecuado y a 5 °CLos resultados contenidos en este Informe de ensayo sólo son válidos para las muestras analizadas.FIN DEL REPORTEPág. 5 de 5 Hermanos Carrera Pinto #159, Parque Industrial Los Libertadores, Colina, Santiago, Chile | Telf +56 2 2654 6104
Annex III Appendix E
557
INFORME DE ENSAYO: 48786/2016Propuesta comercial: 15818/2016.3Arcadis Chile SPAAntonio Varas 621 - Providencia - SantiagoAtención: Ximena OrregoAnálisis Terreno SilalaMuestras recibidas el: 26/12/2016Informe generado el 18/01/2017Pág. 1 de 5 Hermanos Carrera Pinto #159, Parque Industrial Los Libertadores, Colina, Santiago, Chile | Telf +56 2 2654 6104
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Annex III Appendix E
INFORME DE ENSAYO: 48786/2016RESULTADOS ANALÍTICOS Muestras del Item: 1N° ALS483467/2016-1.0483468/2016-1.0483469/2016-1.0Fecha de Muestreo21/12/201622/12/201622/12/2016Hora de Muestreo13:00:0018:15:0016:40:00Tipo de MuestraAguaSuperficialAguaSuperficialAguaSuperficialIdentificaciónSI1-ASILALA1-ISILALA1-IIParámetroCMUnidadLDLQValoresValoresValoresF, Fluoruro11551mg/L0,020,06<0,060,070,08Cl, Cloruro11551mg/L0,030,085,863,503,39ClO3, Clorato11551mg/L0,050,11<0,11<0,11<0,11Br, Bromuro11551mg/L0,050,10<0,10<0,10<0,10SO4, Sulfato11551mg/L0,160,129,8017,7519,00N-NO2, Nitrito11551mg/L0,040,09<0,09<0,09<0,09N-NO3, Nitrato11551mg/L0,020,050,350,310,29P-PO4, Fosfato11551mg/L0,040,13<0,13<0,13<0,13Fecha de Análisis11551---------27/12/2016 10:0027/12/2016 10:0027/12/2016 10:00Conductividad Eléctrica11863μS/cm2,0---382,0255,6262,3Fecha de Análisis11863---------28/12/2016 00:0028/12/2016 00:0028/12/2016 00:00Aluminio Disuelto (Al)12671mg/L---0,01<0,010,020,02Antimonio Disuelto (Sb)12671mg/L---0,00020,00040,00070,0007Arsénico Disuelto (As)12671mg/L---0,00030,05950,07090,0705Bario Disuelto (Ba)12671mg/L---0,00030,00470,00930,0092Berilio Disuelto (Be)12671mg/L---0,00002<0,00002<0,00002<0,00002Bismuto Disuelto (Bi)12671mg/L---0,00002<0,00002<0,00002<0,00002Boro Disuelto (B)12671mg/L---0,0020,2180,2540,294Cadmio Disuelto (Cd)12671mg/L---0,00002<0,00002<0,00002<0,00002Calcio Disuelto (Ca)12671mg/L---0,0624,9916,3216,45Cromo Disuelto (Cr)12671mg/L---0,0001<0,0001<0,00010,0012Cobalto Disuelto (Co)12671mg/L---0,0001<0,0001<0,0001<0,0001Cobre Disuelto (Cu)12671mg/L---0,0005<0,00050,00310,0030Hierro Disuelto (Fe)12671mg/L---0,0060,1160,0460,048Plomo Disuelto (Pb)12671mg/L---0,0004<0,0004<0,0004<0,0004Litio Disuelto (Li)12671mg/L---0,00030,08850,05520,0631Magnesio Disuelto (Mg)12671mg/L---0,00513,9007,5677,302Manganeso Disuelto (Mn)12671mg/L---0,00010,01060,00680,0073Mercurio Disuelto (Hg)12671mg/L---0,0001<0,0001<0,0001<0,0001Molibdeno Disuelto (Mo)12671mg/L---0,00020,00210,00230,0023Niquel Disuelto (Ni)12671mg/L---0,0001<0,0001<0,0001<0,0001Fosforo Disuelto (P)12671mg/L---0,0050,0450,0330,045Potasio Disuelto (K)12671mg/L---0,0095,1104,1604,230Selenio Disuelto (Se)12671mg/L---0,0003<0,0003<0,0003<0,0003Silicio Disuelto (Si)12671mg/L---0,0329,3025,8027,20Plata Disuelta (Ag)12671mg/L---0,00002<0,00002<0,00002<0,00002Sodio Disuelto (Na)12671mg/L---0,0126,7021,1220,50Estroncio Disuelto (Sr)12671mg/L---0,00060,13440,08570,0843Talio Disuelto (Tl)12671mg/L---0,0002<0,0002<0,0002<0,0002Estaño Disuelto (Sn)12671mg/L---0,0005<0,0005<0,0005<0,0005Titanio Disuelto (Ti)12671mg/L---0,0002<0,0002<0,0002<0,0002Uranio Disuelto (U)12671mg/L---0,000060,007570,004410,00442Vanadio Disuelto (V)12671mg/L---0,00030,01690,01900,0190Zinc Disuelto (Zn)12671mg/L---0,0007<0,0007<0,00070,0156Fecha de Análisis12671---------06/01/2017 00:0006/01/2017 00:0006/01/2017 00:00Oxígeno Disuelto14493mg/L0,10---5,636,767,07Fecha de Análisis14493---------26/12/2016 00:0026/12/2016 00:0026/12/2016 00:00Pág. 2 de 5 Hermanos Carrera Pinto #159, Parque Industrial Los Libertadores, Colina, Santiago, Chile | Telf +56 2 2654 6104
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INFORME DE ENSAYO: 48786/2016 Muestras del Item: 1N° ALS483467/2016-1.0483468/2016-1.0483469/2016-1.0Fecha de Muestreo21/12/201622/12/201622/12/2016Hora de Muestreo13:00:0018:15:0016:40:00Tipo de MuestraAguaSuperficialAguaSuperficialAguaSuperficialIdentificaciónSI1-ASILALA1-ISILALA1-IIParámetroCMUnidadLDLQValoresValoresValorespH14524---0,01---7,387,347,41T° de pH14524°C------24,925,125,0Fecha de Análisis14524---------26/12/2016 16:0026/12/2016 16:0026/12/2016 16:00Alcalinidad Bicarbonato14526mg CaCO3/L1,0---169,6105,2106,5Fecha de Análisis14526---------05/01/2017 00:0005/01/2017 00:0005/01/2017 00:00Alcalinidad Carbonato14527mg CaCO3/L1,0---<1,0<1,0<1,0Fecha de Análisis14527---------05/01/2017 00:0005/01/2017 00:0005/01/2017 00:00Filtración de Metales Disueltos (Agua)15779---------sisisiFecha de Análisis15779---------26/12/2016 15:1026/12/2016 15:1026/12/2016 15:10Amoniaco (NH3)17139mg/L0,01---0,010,010,01Fecha de Análisis17139---------04/01/2017 00:0004/01/2017 00:0004/01/2017 00:00 Muestras del Item: 1N° ALS483470/2016-1.0Fecha de Muestreo22/12/2016Hora de Muestreo17:50:00Tipo de MuestraAguaSuperficialIdentificaciónSI3ParámetroCMUnidadLDLQValoresF, Fluoruro11551mg/L0,020,060,09Cl, Cloruro11551mg/L0,030,084,66ClO3, Clorato11551mg/L0,050,11<0,11Br, Bromuro11551mg/L0,050,10<0,10SO4, Sulfato11551mg/L0,160,1212,60N-NO2, Nitrito11551mg/L0,040,09<0,09N-NO3, Nitrato11551mg/L0,020,050,13P-PO4, Fosfato11551mg/L0,040,13<0,13Fecha de Análisis11551---------27/12/2016 10:00Conductividad Eléctrica11863μS/cm2,0---357,0Fecha de Análisis11863---------28/12/2016 00:00Aluminio Disuelto (Al)12671mg/L---0,010,01Antimonio Disuelto (Sb)12671mg/L---0,00020,0004Arsénico Disuelto (As)12671mg/L---0,00030,0225Bario Disuelto (Ba)12671mg/L---0,00030,0035Berilio Disuelto (Be)12671mg/L---0,00002<0,00002Bismuto Disuelto (Bi)12671mg/L---0,00002<0,00002Boro Disuelto (B)12671mg/L---0,0020,285Cadmio Disuelto (Cd)12671mg/L---0,00002<0,00002Calcio Disuelto (Ca)12671mg/L---0,0622,26Cromo Disuelto (Cr)12671mg/L---0,0001<0,0001Cobalto Disuelto (Co)12671mg/L---0,0001<0,0001Cobre Disuelto (Cu)12671mg/L---0,00050,0019Hierro Disuelto (Fe)12671mg/L---0,0060,361Plomo Disuelto (Pb)12671mg/L---0,0004<0,0004Litio Disuelto (Li)12671mg/L---0,00030,0987Magnesio Disuelto (Mg)12671mg/L---0,0058,589Manganeso Disuelto (Mn)12671mg/L---0,00010,0143Mercurio Disuelto (Hg)12671mg/L---0,0001<0,0001Molibdeno Disuelto (Mo)12671mg/L---0,00020,0013Niquel Disuelto (Ni)12671mg/L---0,0001<0,0001Pág. 3 de 5 Hermanos Carrera Pinto #159, Parque Industrial Los Libertadores, Colina, Santiago, Chile | Telf +56 2 2654 6104
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Annex III Appendix E
INFORME DE ENSAYO: 48786/2016 Muestras del Item: 1N° ALS483470/2016-1.0Fecha de Muestreo22/12/2016Hora de Muestreo17:50:00Tipo de MuestraAguaSuperficialIdentificaciónSI3ParámetroCMUnidadLDLQValoresFosforo Disuelto (P)12671mg/L---0,0050,027Potasio Disuelto (K)12671mg/L---0,0095,140Selenio Disuelto (Se)12671mg/L---0,0003<0,0003Silicio Disuelto (Si)12671mg/L---0,0319,90Plata Disuelta (Ag)12671mg/L---0,00002<0,00002Sodio Disuelto (Na)12671mg/L---0,0129,96Estroncio Disuelto (Sr)12671mg/L---0,00060,1311Talio Disuelto (Tl)12671mg/L---0,0002<0,0002Estaño Disuelto (Sn)12671mg/L---0,0005<0,0005Titanio Disuelto (Ti)12671mg/L---0,0002<0,0002Uranio Disuelto (U)12671mg/L---0,000060,01373Vanadio Disuelto (V)12671mg/L---0,00030,0065Zinc Disuelto (Zn)12671mg/L---0,0007<0,0007Fecha de Análisis12671---------06/01/2017 00:00Oxígeno Disuelto14493mg/L0,10---4,17Fecha de Análisis14493---------26/12/2016 00:00pH14524---0,01---8,06T° de pH14524°C------25,1Fecha de Análisis14524---------26/12/2016 16:00Alcalinidad Bicarbonato14526mg CaCO3/L1,0---162,3Fecha de Análisis14526---------05/01/2017 00:00Alcalinidad Carbonato14527mg CaCO3/L1,0---<1,0Fecha de Análisis14527---------05/01/2017 00:00Filtración de Metales Disueltos (Agua)15779---------siFecha de Análisis15779---------26/12/2016 15:10Amoniaco (NH3)17139mg/L0,01---0,01Fecha de Análisis17139---------04/01/2017 00:00Pág. 4 de 5 Hermanos Carrera Pinto #159, Parque Industrial Los Libertadores, Colina, Santiago, Chile | Telf +56 2 2654 6104
Annex III Appendix E
561
INFORME DE ENSAYO: 48786/2016REFERENCIAS DE LOS MÉTODOS DE ENSAYO(*)Parámetros fuera del alcance de acreditación.CMSedeParámetroMétodo de ReferenciaLaboratorio11551SCL Aniones por Cromatografía Iónica(Aguas)US EPA 300.1. 3ed.4ta act 2011.SCL - Inorganico12671SCL Metales Disueltos ICP-MS (Agua)EPA METHOD 6020 A -INDUCTIVELY COUPLEDPLASMA – MASSSPECTROMETRYSCL - Metales14493ANT(*) Oxígeno Disuelto (SM)SM 4500-O-G. Ed 22, 2012.ANT - Inorganico14526ANTAlcalinidad BicarbonatoQWI-IO-ALC-01, Emisión C, mod. 1SM 2320 B, 22nd Edition 2012ANT - Inorganico14527ANTAlcalinidad Carbonato (SM)QWI-IO-ALC-01, Emisión C, mod. 1SM 2320 B, 22nd Edition 2012ANT - Inorganico11863ANTConductividad Eléctrica (SM)QWI-IO-COND-01, Emisión B,mod.4SM 2510 B, 22nd Edition 2012ANT - Inorganico15779ANTFiltración de Metales Disueltos(Agua)SM 3030-B, 21 st ed. 2005ANT - Preparación de muestras17139ANTNH3 Amonio (SM), SubcontratadoETFASM 4500 NH3 DANT - Subcontratado14524ANTpH, Agua (SM)SM 4500-H+ B, 22nd Edition 2012ANT - InorganicoCOMENTARIOSLD = Límite de detecciónLQ = Límite de cuantificaciónLos Límites de Detección y/o Cuantificación para muestras de agua que son indicados en el presente documento, fueron determinadosexperimentalmente en matriz de “Agua Potable”, cabe indicar, que Límites pueden variar dependiendo de la Interferencias propias de cadaMatriz.CM = Código interno del Método de Análisis de ALS Life Sciences Chile S.A.ANT: Juan Gutemberg 438 Galpón 9, Antofagasta, Chile.SCL: Avda. Hermanos Carreras Pinto N°159 Parque Industrial Los Libertadores Colina - Santiago de Chile."EPA": U.S. Environmental Protection Agency."SM": Standard Methods for the Examination of Water and Wastewater."Nch": Norma Chilena."QWI": Procedimiento interno.El presente documento es redactado íntegramente en ALS Life Sciences Chile S.A., su alteración o su uso indebido constituye delito contra lafe pública y se regula por las disposiciones civiles y penales de la materia, queda prohibida la reproducción parcial del presente informe, salvoautorización escrita de ALS Life Sciences Chile S.A.; sólo es válido para las muestras referidas en el presente informe.Las muestras de agua se descartaran 30 días calendarios desde la fecha de emisión del informe de resultados, para el caso de las suelos osedimentos se considerarán 90 días calendario.El presente informe corresponde a 4 muestra(s).El responsable del muestreo es: Cliente quien se responsabiliza por su correcta identificación y preservaciónMuestra(s) recibida(s) en buenas condiciones, en el tipo de recipiente adecuado y a 5 °CLos resultados contenidos en este Informe de ensayo sólo son válidos para las muestras analizadas.FIN DEL REPORTEPág. 5 de 5 Hermanos Carrera Pinto #159, Parque Industrial Los Libertadores, Colina, Santiago, Chile | Telf +56 2 2654 6104
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Annex III Appendix E
Third campaign results
Annex III Appendix E
563
Muestras del Grupo: 5385/2017N° ALS45396/2017-1.045397/2017-1.0Fecha de Muestreo02/02/201702/02/2017Hora de Muestreo12:00:0019:39:00Tipo de MuestraAgua SuperficialAgua SuperficialIdentificación3356528 (SP-SI-31-17)3356529 (BLANK SAMPLE 2)Método de AnálisisParámetroCMUnidadLDLQValorValor--- Aniones por Cromatografía Iónica (Aguas)F, Fluoruro11551mg/L0,020,060,080,47 Aniones por Cromatografía Iónica (Aguas)Cl, Cloruro11551mg/L0,030,082,321,23 Aniones por Cromatografía Iónica (Aguas)ClO3, Clorato11551mg/L0,050,11< 0,11< 0,11 Aniones por Cromatografía Iónica (Aguas)Br, Bromuro11551mg/L0,050,10< 0,10< 0,10 Aniones por Cromatografía Iónica (Aguas)SO4, Sulfato11551mg/L0,160,126,551,51 Aniones por Cromatografía Iónica (Aguas)N-NO2, Nitrito11551mg/L0,040,09< 0,09< 0,09 Aniones por Cromatografía Iónica (Aguas)N-NO3, Nitrato11551mg/L0,020,050,440,17 Aniones por Cromatografía Iónica (Aguas)P-PO4, Fosfato11551mg/L0,040,13< 0,13< 0,13 Aniones por Cromatografía Iónica (Aguas)Fecha de Análisis11551---------07/02/2017 11:0007/02/2017 11:00Conductividad Eléctrica (SM)Conductividad Eléctrica11863μS/cm2,0---192,748,5Conductividad Eléctrica (SM)Fecha de Análisis11863---------08/02/2017 00:0008/02/2017 00:00 Metales Disueltos ICP-MS (Agua)Aluminio Disuelto (Al)12671mg/L---0,010,02< 0,01 Metales Disueltos ICP-MS (Agua)Antimonio Disuelto (Sb)12671mg/L---0,00020,0007< 0,0002 Metales Disueltos ICP-MS (Agua)Arsénico Disuelto (As)12671mg/L---0,00030,07660,0003 Metales Disueltos ICP-MS (Agua)Bario Disuelto (Ba)12671mg/L---0,00030,00400,0004 Metales Disueltos ICP-MS (Agua)Berilio Disuelto (Be)12671mg/L---0,00002< 0,00002< 0,00002 Metales Disueltos ICP-MS (Agua)Bismuto Disuelto (Bi)12671mg/L---0,00002< 0,00002< 0,00002 Metales Disueltos ICP-MS (Agua)Boro Disuelto (B)12671mg/L---0,0020,1980,100 Metales Disueltos ICP-MS (Agua)Cadmio Disuelto (Cd)12671mg/L---0,00002< 0,00002< 0,00002 Metales Disueltos ICP-MS (Agua)Calcio Disuelto (Ca)12671mg/L---0,068,730,42 Metales Disueltos ICP-MS (Agua)Cromo Disuelto (Cr)12671mg/L---0,00010,0015< 0,0001 Metales Disueltos ICP-MS (Agua)Cobalto Disuelto (Co)12671mg/L---0,0001< 0,0001< 0,0001 Metales Disueltos ICP-MS (Agua)Cobre Disuelto (Cu)12671mg/L---0,00050,00090,0007 Metales Disueltos ICP-MS (Agua)Hierro Disuelto (Fe)12671mg/L---0,006< 0,006< 0,006 Metales Disueltos ICP-MS (Agua)Plomo Disuelto (Pb)12671mg/L---0,0004< 0,0004< 0,0004 Metales Disueltos ICP-MS (Agua)Litio Disuelto (Li)12671mg/L---0,00030,03840,0011 Metales Disueltos ICP-MS (Agua)Magnesio Disuelto (Mg)12671mg/L---0,0052,9070,458 Metales Disueltos ICP-MS (Agua)Manganeso Disuelto (Mn)12671mg/L---0,00010,00070,0003 Metales Disueltos ICP-MS (Agua)Mercurio Disuelto (Hg)12671mg/L---0,0001< 0,0001< 0,0001 Metales Disueltos ICP-MS (Agua)Molibdeno Disuelto (Mo)12671mg/L---0,00020,0016< 0,0002 Metales Disueltos ICP-MS (Agua)Niquel Disuelto (Ni)12671mg/L---0,0001< 0,0001< 0,0001 Metales Disueltos ICP-MS (Agua)Fosforo Disuelto (P)12671mg/L---0,0050,036< 0,005 Metales Disueltos ICP-MS (Agua)Potasio Disuelto (K)12671mg/L---0,0093,7100,840 Metales Disueltos ICP-MS (Agua)Selenio Disuelto (Se)12671mg/L---0,0003< 0,0003< 0,0003 Metales Disueltos ICP-MS (Agua)Silicio Disuelto (Si)12671mg/L---0,0326,6018,20 Metales Disueltos ICP-MS (Agua)Plata Disuelta (Ag)12671mg/L---0,00002< 0,00002< 0,00002 Metales Disueltos ICP-MS (Agua)Sodio Disuelto (Na)12671mg/L---0,0116,177,47 Metales Disueltos ICP-MS (Agua)Estroncio Disuelto (Sr)12671mg/L---0,00060,05580,0011 Metales Disueltos ICP-MS (Agua)Talio Disuelto (Tl)12671mg/L---0,0002< 0,0002< 0,0002 Metales Disueltos ICP-MS (Agua)Estaño Disuelto (Sn)12671mg/L---0,00050,0016< 0,0005 Metales Disueltos ICP-MS (Agua)Titanio Disuelto (Ti)12671mg/L---0,0002< 0,0002< 0,0002 Metales Disueltos ICP-MS (Agua)Uranio Disuelto (U)12671mg/L---0,000060,00204< 0,00006 Metales Disueltos ICP-MS (Agua)Vanadio Disuelto (V)12671mg/L---0,00030,0175< 0,0003 Metales Disueltos ICP-MS (Agua)Zinc Disuelto (Zn)12671mg/L---0,0007< 0,0007< 0,0007 Metales Disueltos ICP-MS (Agua)Fecha de Análisis12671---------23/02/2017 00:0023/02/2017 00:00(*) Oxígeno Disuelto (SM)Oxígeno Disuelto14493mg/L0,10---6,695,89(*) Oxígeno Disuelto (SM)Fecha de Análisis14493---------07/02/2017 14:0007/02/2017 14:00pH, Agua (SM)pH14524---0,01---7,895,74pH, Agua (SM)T° de pH14524°C------25,125,0pH, Agua (SM)Fecha de Análisis14524---------07/02/2017 15:0007/02/2017 15:00Alcalinidad BicarbonatoAlcalinidad Bicarbonato14526mg CaCO3/L1,0---67,612,9Alcalinidad BicarbonatoFecha de Análisis14526---------14/02/2017 00:0014/02/2017 00:00Alcalinidad Carbonato (SM)Alcalinidad Carbonato14527mg CaCO3/L1,0---< 1,0< 1,0Alcalinidad Carbonato (SM)Fecha de Análisis14527---------14/02/2017 00:0014/02/2017 00:00Filtración de Metales Disueltos (Agua)Filtración de Metales Disueltos (Agua)15779---------sisiFiltración de Metales Disueltos (Agua)Fecha de Análisis15779---------07/02/2017 16:1407/02/2017 16:14NH3 Amonio (SM), Subcontratado ETFAAmoniaco (NH3)17139mg/L0,01---< 0,01< 0,01NH3 Amonio (SM), Subcontratado ETFAFecha de Análisis17139---------13/02/2017 00:0013/02/2017 00:00
564
Annex III Appendix E
Muestras del Grupo: 5387/2017N° ALS45434/2017-1.045433/2017-1.045432/2017-1.045435/2017-1.045431/2017-1.0Fecha de Muestreo01/02/201701/02/201701/02/201701/02/201701/02/2017Hora de Muestreo11:00:0013:30:0013:40:0015:30:0017:30:00Tipo de MuestraAgua SuperficialAgua SuperficialAgua SuperficialAgua SuperficialAgua SuperficialIdentificación3356543 (SP-SI-10-17)3356542 (R-SI-4-17)3356533 (R-SI-6-17)3356544 (SP-SI-29-17)3356532 (R-SI-3-17)Método de AnálisisParámetroCMUnidadLDLQValorValorValorValorValor--- Aniones por Cromatografía Iónica (Aguas)F, Fluoruro11551mg/L0,020,060,120,080,080,070,07 Aniones por Cromatografía Iónica (Aguas)Cl, Cloruro11551mg/L0,030,082,161,992,012,012,31 Aniones por Cromatografía Iónica (Aguas)ClO3, Clorato11551mg/L0,050,11< 0,11< 0,11< 0,11< 0,11< 0,11 Aniones por Cromatografía Iónica (Aguas)Br, Bromuro11551mg/L0,050,10< 0,10< 0,10< 0,10< 0,10< 0,10 Aniones por Cromatografía Iónica (Aguas)SO4, Sulfato11551mg/L0,160,1214,887,898,136,286,48 Aniones por Cromatografía Iónica (Aguas)N-NO2, Nitrito11551mg/L0,040,09< 0,09< 0,09< 0,09< 0,09< 0,09 Aniones por Cromatografía Iónica (Aguas)N-NO3, Nitrato11551mg/L0,020,050,220,240,230,310,23 Aniones por Cromatografía Iónica (Aguas)P-PO4, Fosfato11551mg/L0,040,13< 0,13< 0,13< 0,13< 0,13< 0,13 Aniones por Cromatografía Iónica (Aguas)Fecha de Análisis11551---------07/02/2017 11:0007/02/2017 11:0007/02/2017 11:0007/02/2017 11:0007/02/2017 11:00Conductividad Eléctrica (SM)Conductividad Eléctrica11863μS/cm2,0---228,4260,3259,8167,3181,3Conductividad Eléctrica (SM)Fecha de Análisis11863---------08/02/2017 00:0008/02/2017 00:0008/02/2017 00:0008/02/2017 00:0008/02/2017 00:00 Metales Disueltos ICP-MS (Agua)Aluminio Disuelto (Al)12671mg/L---0,010,020,020,010,010,03 Metales Disueltos ICP-MS (Agua)Antimonio Disuelto (Sb)12671mg/L---0,0002< 0,00020,00060,00070,00100,0010 Metales Disueltos ICP-MS (Agua)Arsénico Disuelto (As)12671mg/L---0,00030,01140,07450,07450,08460,1055 Metales Disueltos ICP-MS (Agua)Bario Disuelto (Ba)12671mg/L---0,00030,01860,00890,00890,00440,0027 Metales Disueltos ICP-MS (Agua)Berilio Disuelto (Be)12671mg/L---0,00002< 0,00002< 0,00002< 0,00002< 0,00002< 0,00002 Metales Disueltos ICP-MS (Agua)Bismuto Disuelto (Bi)12671mg/L---0,00002< 0,00002< 0,00002< 0,00002< 0,00002< 0,00002 Metales Disueltos ICP-MS (Agua)Boro Disuelto (B)12671mg/L---0,0020,1560,1830,1760,1810,206 Metales Disueltos ICP-MS (Agua)Cadmio Disuelto (Cd)12671mg/L---0,00002< 0,00002< 0,00002< 0,00002< 0,00002< 0,00002 Metales Disueltos ICP-MS (Agua)Calcio Disuelto (Ca)12671mg/L---0,0614,6316,0415,798,599,29 Metales Disueltos ICP-MS (Agua)Cromo Disuelto (Cr)12671mg/L---0,00010,00060,00090,00090,00080,0010 Metales Disueltos ICP-MS (Agua)Cobalto Disuelto (Co)12671mg/L---0,0001< 0,0001< 0,0001< 0,0001< 0,0001< 0,0001 Metales Disueltos ICP-MS (Agua)Cobre Disuelto (Cu)12671mg/L---0,00050,00150,00100,00070,00060,0017 Metales Disueltos ICP-MS (Agua)Hierro Disuelto (Fe)12671mg/L---0,006< 0,006< 0,006< 0,006< 0,006< 0,006 Metales Disueltos ICP-MS (Agua)Plomo Disuelto (Pb)12671mg/L---0,0004< 0,0004< 0,0004< 0,0004< 0,00040,0008 Metales Disueltos ICP-MS (Agua)Litio Disuelto (Li)12671mg/L---0,00030,01230,06030,05830,04590,0719 Metales Disueltos ICP-MS (Agua)Magnesio Disuelto (Mg)12671mg/L---0,0056,2947,1647,1192,7623,664 Metales Disueltos ICP-MS (Agua)Manganeso Disuelto (Mn)12671mg/L---0,00010,00090,00070,00050,00030,0017 Metales Disueltos ICP-MS (Agua)Mercurio Disuelto (Hg)12671mg/L---0,0001< 0,0001< 0,0001< 0,0001< 0,0001< 0,0001 Metales Disueltos ICP-MS (Agua)Molibdeno Disuelto (Mo)12671mg/L---0,00020,00150,00170,00170,00140,0014 Metales Disueltos ICP-MS (Agua)Niquel Disuelto (Ni)12671mg/L---0,0001< 0,0001< 0,0001< 0,0001< 0,0001< 0,0001 Metales Disueltos ICP-MS (Agua)Fosforo Disuelto (P)12671mg/L---0,0050,0470,0410,0410,0380,044 Metales Disueltos ICP-MS (Agua)Potasio Disuelto (K)12671mg/L---0,0096,6803,7403,7002,8102,440 Metales Disueltos ICP-MS (Agua)Selenio Disuelto (Se)12671mg/L---0,0003< 0,0003< 0,0003< 0,0003< 0,0003< 0,0003 Metales Disueltos ICP-MS (Agua)Silicio Disuelto (Si)12671mg/L---0,0330,6025,9025,1019,6019,80 Metales Disueltos ICP-MS (Agua)Plata Disuelta (Ag)12671mg/L---0,00002< 0,00002< 0,00002< 0,00002< 0,00002< 0,00002 Metales Disueltos ICP-MS (Agua)Sodio Disuelto (Na)12671mg/L---0,0111,8618,3918,1314,8116,56 Metales Disueltos ICP-MS (Agua)Estroncio Disuelto (Sr)12671mg/L---0,00060,10120,09280,09220,05700,0574 Metales Disueltos ICP-MS (Agua)Talio Disuelto (Tl)12671mg/L---0,0002< 0,0002< 0,0002< 0,0002< 0,0002< 0,0002 Metales Disueltos ICP-MS (Agua)Estaño Disuelto (Sn)12671mg/L---0,0005< 0,0005< 0,0005< 0,0005< 0,0005< 0,0005 Metales Disueltos ICP-MS (Agua)Titanio Disuelto (Ti)12671mg/L---0,0002< 0,0002< 0,0002< 0,0002< 0,00020,0011 Metales Disueltos ICP-MS (Agua)Uranio Disuelto (U)12671mg/L---0,000060,002480,005000,005010,002340,00281 Metales Disueltos ICP-MS (Agua)Vanadio Disuelto (V)12671mg/L---0,00030,00950,01870,01840,01590,0182 Metales Disueltos ICP-MS (Agua)Zinc Disuelto (Zn)12671mg/L---0,0007< 0,0007< 0,0007< 0,0007< 0,0007< 0,0007 Metales Disueltos ICP-MS (Agua)Fecha de Análisis12671---------23/02/2017 00:0023/02/2017 00:0023/02/2017 00:0023/02/2017 00:0023/02/2017 00:00(*) Oxígeno Disuelto (SM)Oxígeno Disuelto14493mg/L0,10---6,996,966,956,296,73(*) Oxígeno Disuelto (SM)Fecha de Análisis14493---------07/02/2017 14:0007/02/2017 14:0007/02/2017 14:0007/02/2017 14:0007/02/2017 14:00pH, Agua (SM)pH14524---0,01---7,888,588,627,617,93pH, Agua (SM)T° de pH14524°C------25,125,025,125,024,9pH, Agua (SM)Fecha de Análisis14524---------07/02/2017 15:0007/02/2017 15:0007/02/2017 15:0007/02/2017 00:0007/02/2017 15:00Alcalinidad BicarbonatoAlcalinidad Bicarbonato14526mg CaCO3/L1,0---81,6109,5111,664,475,1Alcalinidad BicarbonatoFecha de Análisis14526---------14/02/2017 00:0014/02/2017 00:0014/02/2017 00:0014/02/2017 00:0014/02/2017 00:00Alcalinidad Carbonato (SM)Alcalinidad Carbonato14527mg CaCO3/L1,0---< 1,04,3< 1,0< 1,0< 1,0Alcalinidad Carbonato (SM)Fecha de Análisis14527---------14/02/2017 00:0014/02/2017 00:0014/02/2017 00:0014/02/2017 00:0014/02/2017 00:00Filtración de Metales Disueltos (Agua)Filtración de Metales Disueltos (Agua)15779---------sisisisisiFiltración de Metales Disueltos (Agua)Fecha de Análisis15779---------07/02/2017 16:1407/02/2017 16:1407/02/2017 16:1407/02/2017 16:1407/02/2017 16:14NH3 Amonio (SM), Subcontratado ETFAAmoniaco (NH3)17139mg/L0,01---< 0,01< 0,010,146< 0,010,22NH3 Amonio (SM), Subcontratado ETFAFecha de Análisis17139---------13/02/2017 00:0013/02/2017 00:0013/02/2017 00:0013/02/2017 00:0013/02/2017 00:00
Annex III Appendix E
565
Muestras del Grupo: 5389/2017N° ALS45450/2017-1.045452/2017-1.045453/2017-1.045451/2017-1.045449/2017-1.0Fecha de Muestreo31/01/201731/01/201731/01/201731/01/201731/01/2017Hora de Muestreo15:24:0015:30:0015:50:0017:10:0018:30:00Tipo de MuestraAgua SuperficialAgua SuperficialAgua SuperficialAgua SuperficialAgua SuperficialIdentificación3356541 (R-SI-2-17)3356549 (SP-SI-27-17)3356550 (SP-SI-19-17)3356548 (SP-SI-18-17)3356536 (SP-SI-16-17)Método de AnálisisParámetroCMUnidadLDLQValorValorValorValorValor--- Aniones por Cromatografía Iónica (Aguas)F, Fluoruro11551mg/L0,020,060,080,080,080,080,07 Aniones por Cromatografía Iónica (Aguas)Cl, Cloruro11551mg/L0,030,082,362,032,042,062,09 Aniones por Cromatografía Iónica (Aguas)ClO3, Clorato11551mg/L0,050,11< 0,11< 0,11< 0,11< 0,11< 0,11 Aniones por Cromatografía Iónica (Aguas)Br, Bromuro11551mg/L0,050,10< 0,10< 0,10< 0,10< 0,10< 0,10 Aniones por Cromatografía Iónica (Aguas)SO4, Sulfato11551mg/L0,160,126,276,525,946,085,94 Aniones por Cromatografía Iónica (Aguas)N-NO2, Nitrito11551mg/L0,040,09< 0,09< 0,09< 0,09< 0,09< 0,09 Aniones por Cromatografía Iónica (Aguas)N-NO3, Nitrato11551mg/L0,020,050,220,330,340,340,36 Aniones por Cromatografía Iónica (Aguas)P-PO4, Fosfato11551mg/L0,040,13< 0,13< 0,13< 0,13< 0,13< 0,13 Aniones por Cromatografía Iónica (Aguas)Fecha de Análisis11551---------07/02/2017 11:0007/02/2017 11:0007/02/2017 11:0007/02/2017 11:0007/02/2017 11:00Conductividad Eléctrica (SM)Conductividad Eléctrica11863μS/cm2,0---186,7158,7139,8140,4150,9Conductividad Eléctrica (SM)Fecha de Análisis11863---------08/02/2017 00:0008/02/2017 00:0008/02/2017 00:0008/02/2017 00:0008/02/2017 00:00 Metales Disueltos ICP-MS (Agua)Aluminio Disuelto (Al)12671mg/L---0,010,010,240,230,060,01 Metales Disueltos ICP-MS (Agua)Antimonio Disuelto (Sb)12671mg/L---0,00020,00110,00090,00100,00100,0012 Metales Disueltos ICP-MS (Agua)Arsénico Disuelto (As)12671mg/L---0,00030,10980,08200,08450,08550,0904 Metales Disueltos ICP-MS (Agua)Bario Disuelto (Ba)12671mg/L---0,00030,00130,00220,00280,00180,0020 Metales Disueltos ICP-MS (Agua)Berilio Disuelto (Be)12671mg/L---0,00002< 0,00002< 0,00002< 0,00002< 0,00002< 0,00002 Metales Disueltos ICP-MS (Agua)Bismuto Disuelto (Bi)12671mg/L---0,00002< 0,00002< 0,00002< 0,00002< 0,00002< 0,00002 Metales Disueltos ICP-MS (Agua)Boro Disuelto (B)12671mg/L---0,0020,2350,2010,1690,2100,195 Metales Disueltos ICP-MS (Agua)Cadmio Disuelto (Cd)12671mg/L---0,00002< 0,00002< 0,00002< 0,00002< 0,00002< 0,00002 Metales Disueltos ICP-MS (Agua)Calcio Disuelto (Ca)12671mg/L---0,068,377,666,606,127,06 Metales Disueltos ICP-MS (Agua)Cromo Disuelto (Cr)12671mg/L---0,00010,00040,00050,0005< 0,00010,0004 Metales Disueltos ICP-MS (Agua)Cobalto Disuelto (Co)12671mg/L---0,00010,00040,00100,0008< 0,00010,0010 Metales Disueltos ICP-MS (Agua)Cobre Disuelto (Cu)12671mg/L---0,00050,00080,02730,02340,0053< 0,0005 Metales Disueltos ICP-MS (Agua)Hierro Disuelto (Fe)12671mg/L---0,006< 0,006< 0,0060,031< 0,006< 0,006 Metales Disueltos ICP-MS (Agua)Plomo Disuelto (Pb)12671mg/L---0,0004< 0,0004< 0,0004< 0,0004< 0,0004< 0,0004 Metales Disueltos ICP-MS (Agua)Litio Disuelto (Li)12671mg/L---0,00030,08560,04810,04740,04740,0525 Metales Disueltos ICP-MS (Agua)Magnesio Disuelto (Mg)12671mg/L---0,0053,6333,1072,4632,1752,550 Metales Disueltos ICP-MS (Agua)Manganeso Disuelto (Mn)12671mg/L---0,00010,00130,01180,01050,00200,0019 Metales Disueltos ICP-MS (Agua)Mercurio Disuelto (Hg)12671mg/L---0,0001< 0,0001< 0,0001< 0,0001< 0,0001< 0,0001 Metales Disueltos ICP-MS (Agua)Molibdeno Disuelto (Mo)12671mg/L---0,00020,00120,00120,00120,00110,0012 Metales Disueltos ICP-MS (Agua)Niquel Disuelto (Ni)12671mg/L---0,0001< 0,0001< 0,00010,0004< 0,0001< 0,0001 Metales Disueltos ICP-MS (Agua)Fosforo Disuelto (P)12671mg/L---0,0050,0370,0520,0420,0440,044 Metales Disueltos ICP-MS (Agua)Potasio Disuelto (K)12671mg/L---0,0092,0102,1802,0601,9602,040 Metales Disueltos ICP-MS (Agua)Selenio Disuelto (Se)12671mg/L---0,0003< 0,0003< 0,0003< 0,0003< 0,0003< 0,0003 Metales Disueltos ICP-MS (Agua)Silicio Disuelto (Si)12671mg/L---0,0322,1023,8019,6022,9023,00 Metales Disueltos ICP-MS (Agua)Plata Disuelta (Ag)12671mg/L---0,00002< 0,00002< 0,00002< 0,00002< 0,00002< 0,00002 Metales Disueltos ICP-MS (Agua)Sodio Disuelto (Na)12671mg/L---0,0117,4414,0213,3512,9113,52 Metales Disueltos ICP-MS (Agua)Estroncio Disuelto (Sr)12671mg/L---0,00060,05280,04430,04180,03970,0464 Metales Disueltos ICP-MS (Agua)Talio Disuelto (Tl)12671mg/L---0,0002< 0,0002< 0,0002< 0,0002< 0,0002< 0,0002 Metales Disueltos ICP-MS (Agua)Estaño Disuelto (Sn)12671mg/L---0,0005< 0,0005< 0,0005< 0,0005< 0,0005< 0,0005 Metales Disueltos ICP-MS (Agua)Titanio Disuelto (Ti)12671mg/L---0,0002< 0,00020,00120,0020< 0,0002< 0,0002 Metales Disueltos ICP-MS (Agua)Uranio Disuelto (U)12671mg/L---0,000060,003610,001890,001780,001500,00194 Metales Disueltos ICP-MS (Agua)Vanadio Disuelto (V)12671mg/L---0,00030,01820,01600,01580,01580,0159 Metales Disueltos ICP-MS (Agua)Zinc Disuelto (Zn)12671mg/L---0,0007< 0,0007< 0,00070,0152< 0,0007< 0,0007 Metales Disueltos ICP-MS (Agua)Fecha de Análisis12671---------02/07/2015 00:0002/07/2015 00:0002/07/2015 00:0002/07/2015 00:0002/07/2015 00:00(*) Oxígeno Disuelto (SM)Oxígeno Disuelto14493mg/L0,10---6,657,057,167,017,50(*) Oxígeno Disuelto (SM)Fecha de Análisis14493---------07/02/2017 14:0007/02/2017 14:0007/02/2017 14:0007/02/2017 14:0007/02/2017 14:00pH, Agua (SM)pH14524---0,01---8,627,847,827,817,86pH, Agua (SM)T° de pH14524°C------25,124,925,125,025,0pH, Agua (SM)Fecha de Análisis14524---------07/02/2017 15:0007/02/2017 15:0007/02/2017 15:0007/02/2017 15:0007/02/2017 15:00Alcalinidad BicarbonatoAlcalinidad Bicarbonato14526mg CaCO3/L1,0---78,460,854,151,560,1Alcalinidad BicarbonatoFecha de Análisis14526---------14/02/2017 00:0014/02/2017 00:0014/02/2017 00:0014/02/2017 00:0014/02/2017 00:00Alcalinidad Carbonato (SM)Alcalinidad Carbonato14527mg CaCO3/L1,0---< 1,0< 1,0< 1,0< 1,0< 1,0Alcalinidad Carbonato (SM)Fecha de Análisis14527---------14/02/2017 00:0014/02/2017 00:0014/02/2017 00:0014/02/2017 00:0014/02/2017 00:00Filtración de Metales Disueltos (Agua)Filtración de Metales Disueltos (Agua)15779---------sisisisisiFiltración de Metales Disueltos (Agua)Fecha de Análisis15779---------07/02/2017 16:1407/02/2017 16:1407/02/2017 16:1407/02/2017 16:1407/02/2017 16:14NH3 Amonio (SM), Subcontratado ETFAAmoniaco (NH3)17139mg/L0,01---< 0,010,016< 0,01< 0,01< 0,01NH3 Amonio (SM), Subcontratado ETFAFecha de Análisis17139---------13/02/2017 00:0013/02/2017 00:0013/02/2017 00:0013/02/2017 00:0013/02/2017 00:00
566
Annex III Appendix E
Muestras del Grupo: 5390/2017N° ALS45477/2017-1.045479/2017-1.045481/2017-1.045478/2017-1.045480/2017-1.0Fecha de Muestreo01/02/201731/01/201731/01/201731/01/201731/01/2017Hora de Muestreo11:15:0016:18:0017:55:0018:07:0018:10:00Tipo de MuestraAgua SuperficialAgua SuperficialAgua SuperficialAgua SuperficialAgua SuperficialIdentificación3356537 (SP-SI-8-17)3356540 (SP-SI-1-17)3356547 (SP-SI-17-17)3356538 (SP-SI-15-17)3356546 (SP-SI-28-17)Método de AnálisisParámetroCMUnidadLDLQValorValorValorValorValor--- Aniones por Cromatografía Iónica (Aguas)F, Fluoruro11551mg/L0,020,060,140,090,070,080,08 Aniones por Cromatografía Iónica (Aguas)Cl, Cloruro11551mg/L0,030,081,182,122,062,092,13 Aniones por Cromatografía Iónica (Aguas)ClO3, Clorato11551mg/L0,050,11< 0,11< 0,11< 0,11< 0,11< 0,11 Aniones por Cromatografía Iónica (Aguas)Br, Bromuro11551mg/L0,050,10< 0,10< 0,10< 0,10< 0,10< 0,10 Aniones por Cromatografía Iónica (Aguas)SO4, Sulfato11551mg/L0,160,1211,506,645,816,247,10 Aniones por Cromatografía Iónica (Aguas)N-NO2, Nitrito11551mg/L0,040,09< 0,09< 0,09< 0,09< 0,09< 0,09 Aniones por Cromatografía Iónica (Aguas)N-NO3, Nitrato11551mg/L0,020,050,240,350,340,350,34 Aniones por Cromatografía Iónica (Aguas)P-PO4, Fosfato11551mg/L0,040,13< 0,13< 0,13< 0,13< 0,13< 0,13 Aniones por Cromatografía Iónica (Aguas)Fecha de Análisis11551---------07/02/2017 11:0007/02/2017 11:0007/02/2017 11:0007/02/2017 11:0007/02/2017 11:00Conductividad Eléctrica (SM)Conductividad Eléctrica11863μS/cm2,0---95,3182,9136,5161,2176,3Conductividad Eléctrica (SM)Fecha de Análisis11863---------08/02/2017 00:0008/02/2017 00:0008/02/2017 00:0008/02/2017 00:0008/02/2017 00:00 Metales Disueltos ICP-MS (Agua)Aluminio Disuelto (Al)12671mg/L---0,010,020,020,040,010,05 Metales Disueltos ICP-MS (Agua)Antimonio Disuelto (Sb)12671mg/L---0,00020,00030,00100,00110,00110,0010 Metales Disueltos ICP-MS (Agua)Arsénico Disuelto (As)12671mg/L---0,00030,00920,09350,09220,09190,0900 Metales Disueltos ICP-MS (Agua)Bario Disuelto (Ba)12671mg/L---0,00030,00270,00280,00170,00210,0027 Metales Disueltos ICP-MS (Agua)Berilio Disuelto (Be)12671mg/L---0,00002< 0,00002< 0,00002< 0,00002< 0,00002< 0,00002 Metales Disueltos ICP-MS (Agua)Bismuto Disuelto (Bi)12671mg/L---0,00002< 0,00002< 0,00002< 0,00002< 0,00002< 0,00002 Metales Disueltos ICP-MS (Agua)Boro Disuelto (B)12671mg/L---0,0020,0880,1990,1820,1850,198 Metales Disueltos ICP-MS (Agua)Cadmio Disuelto (Cd)12671mg/L---0,00002< 0,00002< 0,00002< 0,00002< 0,00002< 0,00002 Metales Disueltos ICP-MS (Agua)Calcio Disuelto (Ca)12671mg/L---0,063,959,966,548,459,60 Metales Disueltos ICP-MS (Agua)Cromo Disuelto (Cr)12671mg/L---0,00010,00090,00100,00090,00110,0009 Metales Disueltos ICP-MS (Agua)Cobalto Disuelto (Co)12671mg/L---0,0001< 0,00010,0009< 0,00010,00020,0002 Metales Disueltos ICP-MS (Agua)Cobre Disuelto (Cu)12671mg/L---0,00050,0007< 0,00050,00150,00050,0036 Metales Disueltos ICP-MS (Agua)Hierro Disuelto (Fe)12671mg/L---0,006< 0,006< 0,006< 0,006< 0,006< 0,006 Metales Disueltos ICP-MS (Agua)Plomo Disuelto (Pb)12671mg/L---0,0004< 0,0004< 0,0004< 0,0004< 0,0004< 0,0004 Metales Disueltos ICP-MS (Agua)Litio Disuelto (Li)12671mg/L---0,00030,00800,06050,05090,05560,0579 Metales Disueltos ICP-MS (Agua)Magnesio Disuelto (Mg)12671mg/L---0,0050,4894,1062,1193,0903,908 Metales Disueltos ICP-MS (Agua)Manganeso Disuelto (Mn)12671mg/L---0,00010,00080,00210,00150,00040,0027 Metales Disueltos ICP-MS (Agua)Mercurio Disuelto (Hg)12671mg/L---0,0001< 0,0001< 0,0001< 0,0001< 0,0001< 0,0001 Metales Disueltos ICP-MS (Agua)Molibdeno Disuelto (Mo)12671mg/L---0,00020,00100,00140,00120,00130,0013 Metales Disueltos ICP-MS (Agua)Niquel Disuelto (Ni)12671mg/L---0,0001< 0,00010,0004< 0,0001< 0,0001< 0,0001 Metales Disueltos ICP-MS (Agua)Fosforo Disuelto (P)12671mg/L---0,0050,0170,0490,0420,0430,053 Metales Disueltos ICP-MS (Agua)Potasio Disuelto (K)12671mg/L---0,0092,2502,7102,1202,3602,630 Metales Disueltos ICP-MS (Agua)Selenio Disuelto (Se)12671mg/L---0,0003< 0,0003< 0,0003< 0,0003< 0,0003< 0,0003 Metales Disueltos ICP-MS (Agua)Silicio Disuelto (Si)12671mg/L---0,0320,4021,7018,6019,7022,00 Metales Disueltos ICP-MS (Agua)Plata Disuelta (Ag)12671mg/L---0,00002< 0,00002< 0,00002< 0,00002< 0,00002< 0,00002 Metales Disueltos ICP-MS (Agua)Sodio Disuelto (Na)12671mg/L---0,0110,6615,9713,6614,8815,45 Metales Disueltos ICP-MS (Agua)Estroncio Disuelto (Sr)12671mg/L---0,00060,01130,06010,04500,05130,0579 Metales Disueltos ICP-MS (Agua)Talio Disuelto (Tl)12671mg/L---0,0002< 0,0002< 0,0002< 0,0002< 0,0002< 0,0002 Metales Disueltos ICP-MS (Agua)Estaño Disuelto (Sn)12671mg/L---0,0005< 0,0005< 0,0005< 0,0005< 0,0005< 0,0005 Metales Disueltos ICP-MS (Agua)Titanio Disuelto (Ti)12671mg/L---0,0002< 0,0002< 0,0002< 0,0002< 0,00020,0011 Metales Disueltos ICP-MS (Agua)Uranio Disuelto (U)12671mg/L---0,000060,000120,002510,001700,002080,00207 Metales Disueltos ICP-MS (Agua)Vanadio Disuelto (V)12671mg/L---0,00030,01890,01760,01570,01660,0163 Metales Disueltos ICP-MS (Agua)Zinc Disuelto (Zn)12671mg/L---0,0007< 0,0007< 0,0007< 0,0007< 0,0007< 0,0007 Metales Disueltos ICP-MS (Agua)Fecha de Análisis12671---------23/02/2017 00:0023/02/2017 00:0023/02/2017 00:0023/02/2017 00:0023/02/2017 00:00(*) Oxígeno Disuelto (SM)Oxígeno Disuelto14493mg/L0,10---6,576,977,267,157,06(*) Oxígeno Disuelto (SM)Fecha de Análisis14493---------07/02/2017 14:0007/02/2017 14:0007/02/2017 14:0007/02/2017 14:0007/02/2017 14:00pH, Agua (SM)pH14524---0,01---7,187,647,947,867,61pH, Agua (SM)T° de pH14524°C------25,125,024,924,925,1pH, Agua (SM)Fecha de Análisis14524---------07/02/2017 15:0007/02/2017 15:0007/02/2017 15:0007/02/2017 15:0007/02/2017 15:00Alcalinidad BicarbonatoAlcalinidad Bicarbonato14526mg CaCO3/L1,0---25,882,055,962,372,1Alcalinidad BicarbonatoFecha de Análisis14526---------14/02/2017 00:0014/02/2017 00:0014/02/2017 00:0014/02/2017 00:0014/02/2017 00:00Alcalinidad Carbonato (SM)Alcalinidad Carbonato14527mg CaCO3/L1,0---< 1,0< 1,0< 1,0< 1,0< 1,0Alcalinidad Carbonato (SM)Fecha de Análisis14527---------14/02/2017 00:0014/02/2017 00:0014/02/2017 00:0014/02/2017 00:0014/02/2017 00:00Filtración de Metales Disueltos (Agua)Filtración de Metales Disueltos (Agua)15779---------sisisisisiFiltración de Metales Disueltos (Agua)Fecha de Análisis15779---------07/02/2017 16:1407/02/2017 16:1407/02/2017 16:1407/02/2017 16:1407/02/2017 16:14NH3 Amonio (SM), Subcontratado ETFAAmoniaco (NH3)17139mg/L0,01---< 0,010,1230,255< 0,01< 0,01NH3 Amonio (SM), Subcontratado ETFAFecha de Análisis17139---------13/02/2017 00:0013/02/2017 00:0013/02/2017 00:0013/02/2017 00:0013/02/2017 00:00
Annex III Appendix E
567
Muestras del Grupo: 5391/2017N° ALS45497/2017-1.045494/2017-1.045495/2017-1.045496/2017-1.045498/2017-1.0Fecha de Muestreo01/02/201701/02/201701/02/201701/02/201701/02/2017Hora de Muestreo12:20:0014:00:0015:00:0017:19:0017:19:00Tipo de MuestraAgua SuperficialAgua SuperficialAgua SuperficialAgua SuperficialAgua SuperficialIdentificación3356539 (SP-SI-9-17)3356526 (SP-SI-5-17)3356527 (BLANK SAMPLE)3356535 (R-SI-26-17)3356545 (R-SI-7-17)Método de AnálisisParámetroCMUnidadLDLQValorValorValorValorValor--- Aniones por Cromatografía Iónica (Aguas)F, Fluoruro11551mg/L0,020,060,150,11< 0,060,090,10 Aniones por Cromatografía Iónica (Aguas)Cl, Cloruro11551mg/L0,030,081,091,24< 0,081,881,92 Aniones por Cromatografía Iónica (Aguas)ClO3, Clorato11551mg/L0,050,11< 0,11< 0,11< 0,11< 0,11< 0,11 Aniones por Cromatografía Iónica (Aguas)Br, Bromuro11551mg/L0,050,10< 0,10< 0,10< 0,10< 0,10< 0,10 Aniones por Cromatografía Iónica (Aguas)SO4, Sulfato11551mg/L0,160,129,728,190,168,569,33 Aniones por Cromatografía Iónica (Aguas)N-NO2, Nitrito11551mg/L0,040,09< 0,09< 0,09< 0,09< 0,09< 0,09 Aniones por Cromatografía Iónica (Aguas)N-NO3, Nitrato11551mg/L0,020,050,210,29< 0,050,190,19 Aniones por Cromatografía Iónica (Aguas)P-PO4, Fosfato11551mg/L0,040,13< 0,13< 0,13< 0,13< 0,13< 0,13 Aniones por Cromatografía Iónica (Aguas)Fecha de Análisis11551---------07/02/2017 11:0007/02/2017 11:0007/02/2017 11:0007/02/2017 11:0007/02/2017 11:00Conductividad Eléctrica (SM)Conductividad Eléctrica11863μS/cm2,0---92,188,2< 2,0242,3243,9Conductividad Eléctrica (SM)Fecha de Análisis11863---------08/02/2017 00:0008/02/2017 00:0008/02/2017 00:0008/02/2017 00:0008/02/2017 00:00 Metales Disueltos ICP-MS (Agua)Aluminio Disuelto (Al)12671mg/L---0,010,020,020,030,010,01 Metales Disueltos ICP-MS (Agua)Antimonio Disuelto (Sb)12671mg/L---0,00020,00040,0003< 0,00020,00090,0007 Metales Disueltos ICP-MS (Agua)Arsénico Disuelto (As)12671mg/L---0,00030,01050,0112< 0,00030,06900,0712 Metales Disueltos ICP-MS (Agua)Bario Disuelto (Ba)12671mg/L---0,00030,00510,00390,00080,00850,0084 Metales Disueltos ICP-MS (Agua)Berilio Disuelto (Be)12671mg/L---0,00002< 0,00002< 0,00002< 0,00002< 0,00002< 0,00002 Metales Disueltos ICP-MS (Agua)Bismuto Disuelto (Bi)12671mg/L---0,00002< 0,00002< 0,00002< 0,00002< 0,00002< 0,00002 Metales Disueltos ICP-MS (Agua)Boro Disuelto (B)12671mg/L---0,0020,0850,0980,0190,1710,167 Metales Disueltos ICP-MS (Agua)Cadmio Disuelto (Cd)12671mg/L---0,00002< 0,00002< 0,00002< 0,00002< 0,00002< 0,00002 Metales Disueltos ICP-MS (Agua)Calcio Disuelto (Ca)12671mg/L---0,064,243,79< 0,0615,1514,42 Metales Disueltos ICP-MS (Agua)Cromo Disuelto (Cr)12671mg/L---0,00010,00110,0012< 0,00010,00100,0009 Metales Disueltos ICP-MS (Agua)Cobalto Disuelto (Co)12671mg/L---0,0001< 0,0001< 0,00010,00030,00150,0004 Metales Disueltos ICP-MS (Agua)Cobre Disuelto (Cu)12671mg/L---0,00050,0006< 0,00050,00130,00090,0007 Metales Disueltos ICP-MS (Agua)Hierro Disuelto (Fe)12671mg/L---0,006< 0,006< 0,006< 0,006< 0,006< 0,006 Metales Disueltos ICP-MS (Agua)Plomo Disuelto (Pb)12671mg/L---0,00040,0005< 0,0004< 0,0004< 0,0004< 0,0004 Metales Disueltos ICP-MS (Agua)Litio Disuelto (Li)12671mg/L---0,00030,00760,0079< 0,00030,05920,0562 Metales Disueltos ICP-MS (Agua)Magnesio Disuelto (Mg)12671mg/L---0,0050,5250,5630,0156,5726,407 Metales Disueltos ICP-MS (Agua)Manganeso Disuelto (Mn)12671mg/L---0,00010,00080,00050,00120,00350,0014 Metales Disueltos ICP-MS (Agua)Mercurio Disuelto (Hg)12671mg/L---0,0001< 0,0001< 0,0001< 0,0001< 0,0001< 0,0001 Metales Disueltos ICP-MS (Agua)Molibdeno Disuelto (Mo)12671mg/L---0,00020,00100,0010< 0,00020,00160,0016 Metales Disueltos ICP-MS (Agua)Niquel Disuelto (Ni)12671mg/L---0,0001< 0,0001< 0,00010,0006< 0,00010,0005 Metales Disueltos ICP-MS (Agua)Fosforo Disuelto (P)12671mg/L---0,0050,0230,034< 0,0050,0500,041 Metales Disueltos ICP-MS (Agua)Potasio Disuelto (K)12671mg/L---0,0092,5802,570< 0,0093,6503,550 Metales Disueltos ICP-MS (Agua)Selenio Disuelto (Se)12671mg/L---0,0003< 0,0003< 0,0003< 0,0003< 0,0003< 0,0003 Metales Disueltos ICP-MS (Agua)Silicio Disuelto (Si)12671mg/L---0,0321,1021,90< 0,0326,3025,30 Metales Disueltos ICP-MS (Agua)Plata Disuelta (Ag)12671mg/L---0,00002< 0,00002< 0,00002< 0,00002< 0,00002< 0,00002 Metales Disueltos ICP-MS (Agua)Sodio Disuelto (Na)12671mg/L---0,019,779,41< 0,0117,6617,16 Metales Disueltos ICP-MS (Agua)Estroncio Disuelto (Sr)12671mg/L---0,00060,01530,0173< 0,00060,08450,0875 Metales Disueltos ICP-MS (Agua)Talio Disuelto (Tl)12671mg/L---0,0002< 0,0002< 0,0002< 0,0002< 0,0002< 0,0002 Metales Disueltos ICP-MS (Agua)Estaño Disuelto (Sn)12671mg/L---0,0005< 0,0005< 0,0005< 0,0005< 0,0005< 0,0005 Metales Disueltos ICP-MS (Agua)Titanio Disuelto (Ti)12671mg/L---0,00020,00250,0045< 0,0002< 0,0002< 0,0002 Metales Disueltos ICP-MS (Agua)Uranio Disuelto (U)12671mg/L---0,000060,000100,00013< 0,000060,004750,00480 Metales Disueltos ICP-MS (Agua)Vanadio Disuelto (V)12671mg/L---0,00030,02130,0202< 0,00030,01900,0188 Metales Disueltos ICP-MS (Agua)Zinc Disuelto (Zn)12671mg/L---0,0007< 0,0007< 0,0007< 0,0007< 0,0007< 0,0007 Metales Disueltos ICP-MS (Agua)Fecha de Análisis12671---------23/02/2017 00:0023/02/2017 00:0023/02/2017 00:0023/02/2017 00:0023/02/2017 00:00(*) Oxígeno Disuelto (SM)Oxígeno Disuelto14493mg/L0,10---6,976,657,526,926,83(*) Oxígeno Disuelto (SM)Fecha de Análisis14493---------07/02/2017 14:0007/02/2017 14:0007/02/2017 14:0007/02/2017 14:0007/02/2017 14:00pH, Agua (SM)pH14524---0,01---7,197,754,338,708,67pH, Agua (SM)T° de pH14524°C------25,125,124,925,024,9pH, Agua (SM)Fecha de Análisis14524---------07/02/2017 15:0007/02/2017 15:0007/02/2017 15:0007/02/2017 15:0007/02/2017 15:00Alcalinidad BicarbonatoAlcalinidad Bicarbonato14526mg CaCO3/L1,0---26,827,9< 1,0108,494,8Alcalinidad BicarbonatoFecha de Análisis14526---------28/02/2017 00:0014/02/2017 00:0014/02/2017 00:0014/02/2017 00:0014/02/2017 00:00Alcalinidad Carbonato (SM)Alcalinidad Carbonato14527mg CaCO3/L1,0---< 1,0< 1,0< 1,04,310,7Alcalinidad Carbonato (SM)Fecha de Análisis14527---------28/02/2017 00:0014/02/2017 00:0014/02/2017 00:0014/02/2017 00:0014/02/2017 00:00Filtración de Metales Disueltos (Agua)Filtración de Metales Disueltos (Agua)15779---------sisisisisiFiltración de Metales Disueltos (Agua)Fecha de Análisis15779---------07/02/2017 16:1407/02/2017 16:1407/02/2017 16:1407/02/2017 16:1407/02/2017 16:14NH3 Amonio (SM), Subcontratado ETFAAmoniaco (NH3)17139mg/L0,01---< 0,01< 0,01< 0,01< 0,01< 0,01NH3 Amonio (SM), Subcontratado ETFAFecha de Análisis17139---------13/02/2017 00:0014/02/2017 00:0014/02/2017 00:0014/02/2017 00:0014/02/2017 00:00
568
Annex III Appendix E
Volume 4 - Annexes I-III to the Expert Reports