Prepared in cooperation with the Afghanistan Geological Survey and the

U.S. Department of Defense Task Force for Business and Stability Operations

Hydrogeology and Water Quality of the 

Chakari Basin, Afghanistan

U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2014–5113

USGS Afghanistan Project Product No. 263
Cover. View of the Chakari Basin in the Khaki Jabbar District, Afghanistan, from the north looking south. Photograph courtesy of Drew Craig, 

SRK Exploration Services, used with permission. 
Hydrogeology and Water Quality of the 

Chakari Basin, Afghanistan

By Thomas J. Mack, Michael P. Chornack, Sarah M. Flanagan, and 

Ann T. Chalmers

Prepared in cooperation with the Afghanistan Geological Survey and the 

U.S. Department of Defense Task Force for Business and Stability Operations

Scientific Investigations Report 2014–5113

USGS Afghanistan Project Product No. 263

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

SALLY JEWELL, Secretary

U.S. Geological Survey

Suzette M. Kimball, Acting Director

U.S. Geological Survey, Reston, Virginia: 2014

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Suggested citation:

Mack, T.J., Chornack, M.P., Flanagan, S.M., and Chalmers, A.T., 2014, Hydrogeology and water quality of the 

Chakari Basin, Afghanistan: U.S. Geological Survey Scientific Investigations Report 2014–5113, 35 p., 

http://dx.doi.org/10.3133/sir20145113.

ISSN 2328-031X (print)

ISSN 2328-0328 (online)

ISBN 978-1-4113-3807-4
iii

Acknowledgements

We wish to acknowledge the efforts of our colleagues at the Afghanistan Geological Survey 

(AGS), Hydrogeology Group, and particularly the North Aynak-Taghar field team consisting of 

engineers Ali Mohammad Aslami, Fazli Burhanadin, and Saed Jamaluddin (formerly AGS). Neil 

Plummer, U.S. Geological Survey (USGS; emeritus), contributed considerably to the analysis and 

understanding of isotope analysis and in particular the analysis of carbon-14 and tritium-tohelium dating data. We also wish to acknowledge the village elders who gave access to wells 

used in this study. Thanks also go to Mohammad Fahim Zaheer (USGS liaison), Denise Argue 

(USGS), personnel with the Task Force for Business and Stability Operations, and other individuals whose contributions have made this work possible.

v

Contents

Acknowledgements......................................................................................................................................iii

Abstract...........................................................................................................................................................1

Introduction.....................................................................................................................................................1

Description of Study Area ...................................................................................................................3

Geographic Setting......................................................................................................................3

Climate and Vegetation...............................................................................................................3

Population and Water Use .........................................................................................................4

Purpose and Scope ..............................................................................................................................6

Methods of Investigation.....................................................................................................................6

Hydrogeologic Data.....................................................................................................................6

Water-Quality Data......................................................................................................................6

Hydrogeology..................................................................................................................................................8

Surface Water.......................................................................................................................................9

Geology...................................................................................................................................................9

Bedrock .........................................................................................................................................9

Unconsolidated Sediments ......................................................................................................11

Basin-Fill Aquifer Thickness .............................................................................................................12

Water-Level Fluctuations...................................................................................................................12

Groundwater Flow and Storage .......................................................................................................12

Water Quality, Chemistry, and Isotopes...................................................................................................17

Surface Water.....................................................................................................................................17

Groundwater........................................................................................................................................17

Mass-Concentration Ratios .....................................................................................................17

Nutrients......................................................................................................................................23

Bacteria.......................................................................................................................................23

Oxidation-Reduction Conditions..............................................................................................23

Trace Elements...........................................................................................................................23

Inorganic and Anthropogenic Tracer Constituents..............................................................25

Nitrogen and Oxygen Isotopes of Nitrate.....................................................................25

Hydrogen and Oxygen Isotopes of Water.....................................................................26

Chlorofluorocarbons and Sulfur Hexafluoride.............................................................26

Tritium, Helium, and Carbon-14 Isotopes ......................................................................26

Summary and Conclusions.........................................................................................................................30

References Cited..........................................................................................................................................31

Appendix 1. Physical Properties, Nutrient, Bacteria, and Major Ion Water-Quality Data 

for the Chakari Basin, Afghanistan .............................................................................................35

Appendix 2. Trace-Element Water-Quality Data for the Chakari Basin, Afghanistan...................35

Appendix 3. Inorganic and Anthropogenic Tracer and Dissolved Gas Data for the Chakari 

Basin, Afghanistan.........................................................................................................................35
vi

Figures

1. Map showing major geographic features of the Chakari Basin, Afghanistan...................2

2. Graph showing mean monthly precipitation in Kabul, Afghanistan, from 1957 

through 1977 and from 2003 through 2012 and mean monthly streamflow at the 

Chakari River between 1965 and 1980.......................................................................................4

3. Map showing villages and estimated population in the Chakari Basin, Afghanistan.......5

4. Map showing locations of wells, springs, karezes, and streams in the Chakari Basin 

sampling network, Afghanistan..................................................................................................7

5. Map showing generalized geology and topography in the study area in the Chakari 

Basin, Afghanistan .....................................................................................................................10

6. Photograph showing coarse-grained sediments in a stream channel on the 

west side of the Chakari Basin, Afghanistan, looking A, north and B, south ...................13

7. Map showing the thickness of unconsolidated and semiconsolidated sediments 

in the Chakari Basin, Afghanistan............................................................................................14

8. Hydrograph of well W5 (Danish Committee for Aid to Afghan Refugees 

well GMW–4) in the Chakari Basin and total monthly precipitation in Kabul, 

Afghanistan, 2005 through 2011................................................................................................15

9. Map showing water-table elevation and direction of groundwater flow in the 

Chakari Basin, Afghanistan.......................................................................................................16

10. Map showing specific conductance of water in the Chakari Basin, Afghanistan, 

2012–2013 .....................................................................................................................................21

11. Map showing dissolved solids concentrations in water in the Chakari Basin, 

Afghanistan, 2012–2013 .............................................................................................................22

12. Map showing nitrate plus nitrite concentrations in water in the Chakari Basin, 

Afghanistan, 2012–2013 .............................................................................................................24

13. Graph showing the isotopic composition of the nitrate in water samples from the 

Chakari Basin, 2012–2013 ..........................................................................................................25

14. Graph showing the hydrogen-2 (2H) versus oxygen-18 (18O) isotopic composition, 

relative to Vienna Standard Mean Ocean Water, of rivers and groundwater in the 

Chakari and Kabul Basins, Afghanistan..................................................................................27

15. Graphs showing carbon-14 activities in relation to concentrations of chlorofluorocarbons (CFCs) A, trichlorofluoromethane (CFC–11), B, dichlorodifluoromethane 

(CFC–12), C, trichlorotrifluoroethane (CFC–113), and D, sulfur hexafluoride (SF6

) in 

groundwater samples from the Chakari Basin, Afghanistan, 2012–2013 ..........................29

Tables

1. Annual and long-term average precipitation and temperature at the Afghanistan 

Agrometeorological Project station in Kabul, Afghanistan...................................................3

2. Wells, kareze, springs, and stream sampled in the Chakari Basin, Afghanistan...............8

3. Hydrogeologic groups in the Chakari Basin, Afghanistan...................................................11

4. Summary statistics for selected physical properties, inorganic water-quality 

constituents, and raw and modeled isotopes in groundwater samples collected by 

the Afghanistan Geological Survey from eight wells, four springs, and one kareze in 

Chakari Basin, Afghanistan, 2012–3 ........................................................................................18
vii

Conversion Factors, Datum, and Abbreviations

International System (SI) to Inch/Pound

Multiply By To obtain

Length

millimeter (mm) 328.1 foot (ft)

centimeter (cm) 32.81 foot (ft)

meter (m) 3.281 foot (ft)

kilometer (km) 0.6214 mile (mi)

Area

square meter (m2

) 10.76 square foot (ft2)

square kilometer (km2

) 0.3861 square mile (mi2)

Volume

liter (L) 0.2642 gallon (gal)

cubic meter (m3

) 264.2 gallon (gal)

cubic meter (m3

) 35.31 cubic foot (ft3)

Flow rate

meter per second (m/s) 3.281 foot per second (ft/s)

meter per day (m/d) 3.281 foot per day (ft/d)

meter per year (m/y) 3.281 foot per year (ft/y)

cubic meter per second (m3

/s) 35.31 cubic foot per second (ft3/s)

cubic meter per second per square kilometer 

[(m3

/s)/km2]

91.49 cubic foot per second per square mile 

[(ft3/s)/mi2]

cubic meter per day (m3

/d) 35.31 cubic foot per day (ft3/d)

liter per second (L/s) 15.85 gallon per minute (gal/min)

liter per minute 0.2642 gallon per minute (gal/min)

liter per day 0.2642 gallon per day (gal/d)

Vertical and horizontal coordinate information is referenced to the World Geodetic System of 

1984 (WGS 84).

Elevation, as used in this report, refers to distance above the vertical datum.

Specific conductance is given in microsiemens per centimeter at 25 degrees Celsius (μS/cm at 

25 °C).

Concentrations of chemical constituents in water are given either in milligrams per liter (mg/L) 

or micrograms per liter (μg/L).
viii

Delta notation for reporting of isotope data.—Stable isotope data are reported as a ratio relative 

to the ratio of a standard. For example, 18O/16O of a sample is compared with 18O/16O of a standard 

by the relation: δ18O = (Rsample/Rstandard – 1) × 1,000, where Rsample = 18O/16O in the sample, 

Rstandard = 18O/16O in the standard, and δ18O = relative difference in concentration, in parts per 

thousand (per mil). Delta 18O (δ18O) is referred to as delta notation and is the value reported by 

isotopic laboratories for stable isotope analysis. Deuterium, designated as δ2H, can be derived 

by analogy to δ18O where the ratio 2H:H replaces 18O/16O in Rsample and Rstandard. The standard 

used for determining δ18O and δ2H in water used in this report is Vienna standard mean ocean 

water (VSMOW). If δ18O and δ2H samples contain more of the heavier isotopes (18O or 2H) than 

the reference material, the samples have positive per mil values and are referred to as heavier 

than the reference material or as being enriched in the heavier isotope. Conversely, if the 

samples contain more of the lighter isotopes (16O or H) than the reference material, the samples 

have negative per mil values and are referred to as lighter than the reference material or as 

being depleted in the heavier isotope. For example, a δ18O value of –18.15 per mil can be referred 

to as lighter than VSMOW or depleted in 18O relative to VSMOW.

Place names given in this report are anglicized translations from the Dari language; however, 

there may not be a universally accepted English language translation for many names. This 

report attempts to use the most commonly used translation where possible, but the reader is 

cautioned that other variants of names may be in use.

Abbreviations

AGS Afghanistan Geological Survey

DOD U.S. Department of Defense

NGO nongovernmental organization

TFBSO Task Force for Business and Stability Operations

USGS U.S. Geological Survey
Hydrogeology and Water Quality of the Chakari Basin, 

Afghanistan

By Thomas J. Mack, Michael P. Chornack, Sarah M. Flanagan, and Ann T. Chalmers

Abstract

The hydrogeology and water quality of the Chakari 

Basin, a 391-square-kilometer (km2

) watershed near Kabul, 

Afghanistan, was assessed by the U.S. Geological Survey 

and the Afghanistan Geological Survey to provide an 

understanding of the water resources in an area of Afghanistan 

with considerable copper and other mineral resources. Water 

quality, chemical, and isotopic samples were collected 

at eight wells, four springs, one kareze, and the Chakari 

River in a basin-fill aquifer in the Chakari Basin by the 

Afghanistan Geological Survey. Results of water-quality 

analyses indicate that some water samples in the basin had 

concentrations of chemical constituents that exceeded World 

Health Organization guidelines for nitrate, sodium, and 

dissolved solids and some of the samples also had elevated 

concentrations of trace elements, such as copper, selenium, 

strontium, uranium, and zinc. Chemical and isotopic analyses, 

including for tritium, chlorofluorocarbons, and carbon-14, 

indicate that most wells contain water with a mixture of 

ages from young (years to decades) to old (several thousand 

years). Three wells contained groundwater that had modeled 

ages ranging from 7,200 to 7,900 years old. Recharge from 

precipitation directly on the basin-fill aquifer, which covers an 

area of about 150 km2, is likely to be very low (7 × 10-5 meters 

per day) or near zero. Most recharge to this aquifer is likely 

from rain and snowmelt on upland areas and seepage losses 

and infiltration of water from streams crossing the basinfill aquifer. It is likely that the older water in the basin-fill 

aquifer is groundwater that has travelled along long and (or) 

slow flow paths through the fractured bedrock mountains 

surrounding the basin. The saturated basin-fill sediments in 

most areas of the basin are probably about 20 meters thick 

and may be about 30 to 60 meters thick in most areas near the 

center of the Chakari Basin. The combination of low recharge 

and little storage indicates that groundwater resources are 

likely to be limited. Groundwater use in the villages of the 

basin is generally supplied by hand-pumped wells, whereas 

agricultural needs are met by surface-water flows. New or 

increased water uses in the basin, or activities that may affect 

water quality, should be carefully evaluated to avoid affecting 

existing uses.

Introduction

Afghanistan’s mineral resources are a potential means of 

achieving economic growth that may greatly benefit the country’s stability. Water is needed not only to process the minerals 

but also to supply existing communities and the associated 

community growth that may accompany a developing mining 

economy. For the development of the mineral resources of an 

area to be sustainable and have minimal adverse effects, the 

quality and quantity of water in the streams and aquifers in the 

area must be assessed relative to the needs of both the local 

population and potential future mining activities. The Chakari River Basin is a 391-square-kilometer (km2

) area about 

20 kilometers (km) southeast of the city of Kabul (fig. 1). The 

basin contains considerable copper, cobalt, and chromium 

minerals in addition to other deposits (Peters and others, 

2011). Thus, the Chakari River Basin was well suited as a pilot 

mineral resource area for the Afghanistan Geological Survey 

(AGS) to develop and demonstrate capabilities for conducting 

geologic and hydrologic investigations.

In 2012–2013, the U.S. Geological Survey (USGS), in 

collaboration with hydrologic engineers at the Afghanistan 

Geological Survey (AGS), conducted hydrogeologic 

investigations of the Chakari Basin under an agreement 

supported by the U.S. Department of Defense Task Force 

for Business and Stability Operations (TFBSO). The 

hydrogeologic investigations compiled existing data from 

nongovernmental organizations (NGOs), Afghan ministries, 

and geologic studies together with field data collected by 

the AGS to provide an understanding of the hydrogeology 

of the basin. The investigation of the Chakari Basin focused 

on the basic aquifer properties of the basin-fill aquifer, 

including aquifer boundaries, recharge, discharge, direction 

of groundwater flow, saturated thickness, and storage. A 

team of hydrologic engineers from the AGS conducted field 

investigations in the study area that included inventorying 

wells, identifying water quality and isotopic sampling 

locations, collecting surface and groundwater samples, and 

making hydrologic observations on the discharges of springs 

and karezes. This report presents results and interpretation of 

the hydrogeologic and field investigations.
2 Hydrogeology and Water Quality of the Chakari Basin, Afghanistan

69°20'E 69°30'E

34°20'N

34°10'N

Afghanistan

0 2 4 6 8 KILOMETERS Base from U.S. Geological Survey shuttle radar topography mission, 85-meter resolution, 2000

Universal Transverse Mercator projection, Zone 42 N, World Geodetic System, 1984 

Boundary of Chakari Basin

Inset map area—Shows area of

 figures 4, 7, 9, 10, 11 and 12

0 1 2 3 4 MILES

Perennial stream

Drainage network—Generated from 85-meter 

 digital elevation model data

Band-i-Amin Ghazi historical

 streamgage on the Chakari River

Village

Ephemeral stream

Kabul

Turkmenistan

Iran

Pakistan

Study 

area 

EXPLANATION

Band-i-Amin Ghazi 

Reservoir

Band-i-Amin Ghazi 

streamgage

Taghar

Aynak

Khaki Jabbar

Malang

Chakari

Chakari River

0

0 150 300 Mi

150 450 300 600 Km

Figure 1. Major geographic features of the Chakari Basin, Afghanistan.
Introduction 3

Description of Study Area

The study area, herein described as the Chakari Basin, 

encompasses a 391-km2

 watershed formed by the Chakari 

River in the western half of the Khaki Jabar District (fig. 1). 

The North Aynak-Taghar mineral investigation recently (2013) 

undertaken by the AGS, the TFBSO, and the USGS was 

conducted in an area along the southern slope of the mountain 

ridge that forms the northern boundary of the Chakari Basin, 

near the villages of Aynak and Taghar (fig. 1). Known mineral 

deposits, including numerous copper and cobalt ore bodies and 

several ore bodies containing chromium, talc and magnesite, 

and asbestos are hosted in sedimentary rocks surrounding and 

within the Chakari Basin (Peters and others, 2011).

Geographic Setting

The Chakari Basin is surrounded by steep mountain 

ridges, except for a section about 6 km in length along the 

northeastern boundary of the basin, adjacent to the eastern 

part of the Khaki Jabar District. The only drainage outlet is 

the Chakari River, which flows northward out of the basin 

in the center of the northern ridge (fig. 1). A few ephemeral 

streams drain the surrounding hills and ridges and are tributaries to the Chakari River. The average elevation of the hills 

and ridges surrounding the basin is 2,900 meters (m) above 

World Geodetic System of 1984 (WGS 84), with a few peaks 

rising above 3,300 m (Bohannon, 2010). The lowest point 

in the basin is 2,050 m at the Band-i-Amir Ghazi Reservoir 

(coincident with the streamgage symbol on fig. 1). The floor of 

the basin can be defined approximately by the 2,350-m topographic contour line (Bohannon, 2010). The transition from 

the basin floor to the surrounding hills and ridges is marked 

by variously sized alluvial fans with angles of repose from 3 

to 9 degrees. The best developed alluvial fans are on the hills 

and ridges that form the northern boundary of the basin. The 

hills and ridges that surround the basin have steep slopes, have 

very narrow peaks and are dissected by incised ephemeral 

drainages. The southern upland areas of the Chakari Basin are 

extremely rugged (cover and fig. 1).

Climate and Vegetation

The climate in the study area is semiarid. The summers are typically hot and dry, and the winters are cold with 

rain and snow. The Afghanistan Agrometeorological Project 

(Agromet) operates a meteorological station in the city of 

Kabul approximately 20 km northwest of the study area. 

The Kabul Agromet station is close to the study area, but the 

elevation of the valley floor in the Chakari Basin is more than 

300 m higher than the city of Kabul. The precipitation patterns 

between the two areas may be similar, but the higher elevation of the Chakari Basin likely results in lower temperatures 

that could affect the amount and type of precipitation. The 

study area is in the Capital region of the Agromet network; 

this region includes several precipitation stations (Afghanistan Agrometeorological Project, 2010). The annual observed 

total precipitation for water year1

 2010 for the Capital region 

ranged from 221 to 300 millimeters (mm; Afghanistan 

Agrometeorological Project, 2010, Seasonal Bulletin map 2). 

Summary statistics for the Kabul Agromet station are listed in 

table 1. Monthly mean precipitation is shown in figure 2 for 

two periods of record, 1957 through 1977 (Favre and Kamal, 

2004) and 2003 through 2012 (Afghanistan Agrometerological Project, 2013). The two short-term records are similar, 

with higher precipitation amounts in the late fall through early 

spring, although precipitation appears to be higher in recent 

summer months (fig. 2).

1

The Afghan water year is the 12-month period from September 1 through 

August 31 designated by the calendar year in which it ends.

Table 1. Annual and long-term average precipitation and temperature at the Afghanistan Agrometeorological Project station in Kabul, 

Afghanistan.

[Station is about 20 kilometers northwest of the Chakari Basin, Afghanistan. Elevation refers to distance above the World Geodetic System of 1984 vertical 

datum. Long-term averages are based on data from 1942 through 1993 and 2005 through 2010 as reported in Afghanistan Agrometeorological Project (2010). 

Agromet, Afghanistan Agrometeorological Project; km, kilometers; m, meters; mm, millimeters; °C, degrees Celsius]

Agromet 

station

Distance from 

study area center, 

in km

Elevation, 

in m

Precipitation, 

in mm

Temperature, long-term average, 

in °C

Annual, water 

year 2010a

Long-term average Minimum 

and month Mean Maximum

Annual Minimum and 

months

Maximum 

and month

Kabul 24 1,810 304.3 317.5 1.2 June and August 83.2 April -2.6 January 9.8 24.8

a

Water year is the 12-month period September 1 through August 31 designated by the calendar year in which it ends.
4 Hydrogeology and Water Quality of the Chakari Basin, Afghanistan

0.01

0.1

1

1

10

100

Oct. Nov. Dec. Jan. Feb. Mar. Apr. May June July Aug. Sept.

Mean monthly streamflow, in cubic meters per second

Mean monthly precipitation, in millimeters

Month

Precipitation 2003–2012

Precipitation 1957–1977

Streamflow 1965–1980

Figure 2. Mean monthly precipitation in Kabul, Afghanistan, from 1957 through 1977 (Favre and Kamal, 

2004) and from 2003 through 2012 (Afghanistan Agrometeorological Project, 2013) and mean monthly 

streamflow at the Chakari River between 1965 and 1980 (Olson and Williams-Sether, 2010).

The natural vegetation in Afghanistan has been degraded 

during the past several decades by overgrazing and harvesting 

for fuel and building materials (Breckle, 2007). In the study 

area, the lower elevations are classified as Pistacia atlantica 

(pistachio) and Amygdalus (almond) woodlands. However, 

there is very little actual woodland in the basin apart from 

some stands of small trees where the Chakari River flows into 

the Band-i-Amir Ghazi Reservoir (coincident with the historical Band-i-Amir Ghazi streamgage symbol on fig. 1). Irrigated 

fields, small orchards, and pastures are present in the valleys in 

the study area wherever water can be accessed. The study area 

above the valley floor has very sparse vegetation.

Population and Water Use

Currently there is no formal population count in 

Afghanistan; however, the Central Statistics Organization 

(2013) estimated the population of the Khaki Jabar District, 

which is the least populated district in the Kabul Province, to 

be 13,900. The 2011 population estimated by LandScan (Oak 

Ridge National Laboratory, 2012), which uses population 

indicators such as nighttime lights, roads, and buildings, was 

21,556 for the Khaki Jabar District and 10,703 for the study 

area. The population density shown in figure 3 has a pixel 

resolution of about 1 km2

 (Oak Ridge National Laboratory, 

2012). The high, rugged mountains in the study area are likely 

uninhabited regardless of the estimates in figure 3. About one 

third of the population is in about 10 villages with estimated 

populations of 200 to more than 300 people in the northern 

half of the basin. The extreme southern upland, area of the 

basin is rugged and much less populated.

Most villages have several dug wells and one or more 

tube wells installed in unconsolidated sediments by NGOs. 

Most wells have hand pumps; therefore, per capita water use 

in the study area is likely to be minimal and may be on the 

order of 20 to 30 liters per day (L/d; Mack and others, 2010). 

Given the estimated population and per capita use rates, total 

drinking-water use in the basin may amount to only 200 to 

300 cubic meters per day (m3/d). Irrigation water use in the 

study area is likely to be an order of magnitude or greater than 

drinking water use and generally is served by seasonal flow 

from springs, karezes, or streams.

Some villages may also be served by karezes. Before 

the Afghan revolution (1980), nearly all water supply in the 

Chakari Basin was from either dug wells or karezes; few, if 

any, small-diameter cased wells were installed in the Chakari 

Basin. A kareze is a hand dug, gravity-fed water-supply tunnel conduit system that accesses the groundwater table and 
Introduction 5

69°20'E 69°30'E

34°20'N

34°10'N

Base from U.S. Geological Survey shuttle radar

topography mission, 2000, 85-meter resolution

Universal Transverse Mercator projection, 

Zone 42 N, World Geodetic System, 1984 

Boundary of Chakari Basin

Perennial stream

Drainage network—Generated from 85-meter 

 digital elevation model data

Named village

Streamgage

Ephemeral stream

EXPLANATION

25 to 50

>50 to 100

>100 to 150

>150 to 350

Inset map area—Shows area of

 figures 4, 7, 9, 10, 11 and 12

Population density, in people 

 per square kilometer—Oak Ridge 

 National Laboratory (2012) 

0 2 4 6 8 KILOMETERS

0 1 2 3 4 MILES

Chakari River

Band-i-Amin Ghazi 

Reservoir

Taghar

Mirza Khan

Kharoti

Aynak

Khurd

Kabul

Dawran

Khel

Shuman Zay

Malang

Chakari

Chakari

Figure 3. Villages and estimated population in the Chakari Basin, Afghanistan. Population density data are from Oak Ridge 

National Laboratory (2012).
6 Hydrogeology and Water Quality of the Chakari Basin, Afghanistan

works consistently in stable climates. However, the kareze 

supply conduit requires periodically removing fine-grained 

sediment, which may represent a considerable effort and can 

be hazardous because of unstable tunnel walls. Additionally, drilled wells near the source of a kareze may lower the 

local water table and cause karezes to become dry. Since the 

1980s, the population in the Chakari Basin, similar to many 

areas of Afghanistan, has become more reliant on drilled wells 

and less so on karezes. At least seven karezes can be identified, primarily in western areas of the study area, using aerial 

photography (fig. 4). The karezes have lengths, from the outlet 

to the furthest visible upgradient access hole, of approximately 

100 to 1,250 m. Two of the larger karezes are still functioning 

as agricultural water supplies, whereas the others appear to be 

inactive. Based on aerial photography, kareze K1 appears to 

have a source in an ephemeral drainage about 700 m west of 

its outlet.

Purpose and Scope

The purpose of this report is to (1) describe the 

hydrogeologic characteristics of the basin-fill aquifer, 

including areal extent of the basin-fill aquifer, water-table 

elevations, general directions of groundwater flow, and 

saturated thickness; (2) provide a general estimate of water 

availability; and (3) assess the general quality of the water 

resources in the Chakari Basin.

Methods of Investigation

The hydrogeology and water quality of water resources 

in the Chakari Basin were characterized through the use of 

geologic mapping, information contained in well records, 

historical streamflow and groundwater-level data, and recent 

water-quality sampling. Geologic maps in combination 

with data contained in well completion and borehole logs 

provide information on extent, composition, thickness, and 

saturation of the unconsolidated sediments of the aquifer. 

Historical streamflows, groundwater-level data, and chemical 

and isotopic tracers were analyzed to assess recharge in the 

basin. Water quality was described through the use of recently 

collected surface-water and groundwater samples.

AGS engineers examined the study area for accessible 

wells, springs, karezes, and streams for investigation in the 

more populated northern areas of the Chakari Basin. Eight 

wells, one kareze, four springs, and one stream were inventoried and sampled for this study (fig. 4). The locations, depths 

to water, well depths, and other information are provided in 

table 2. The wells and kareze investigated were in villages 

shown on figure 3.

Security concerns greatly restricted the time that AGS 

and USGS personnel could spend in the field and the locations 

that they could access. Because of these limitations, existing 

spatial, mapping, and well data were used as much as possible.

Hydrogeologic Data

Hydrogeologic data and information used in this study 

were also obtained from geologic maps and from wells and 

boreholes in the basin. Boreholes drilled for the North AynakTaghar mineral investigation (SRK Exploration Services, 

written commun., 2013) provided insight into the hydraulic 

properties of bedrock in the area (fig. 4). Additionally, watersupply well data compiled by the NGO Danish Committee for 

Aid to Afghan Refugees (DACAAR) provided information on 

distribution of drilled wells, depth to water, and well depths 

in the basin (Danish Committee for Aid to Afghan Refugees, 

2011). No hydraulic tests have been conducted in the study 

area; however, hydraulic properties from other investigations (Böckh, 1971; Abdullah and Chmyriov, 1977; Mack and 

others, 2010), inferred from drillers logs of wells in Kabul 

(Jaron Andres, U.S. Army Geospatial Center, written commun., 2013) and boreholes (fig. 4) for the North Aynak-Tahgar 

mineral investigation (Drew Craig, SRK Exploration Services, 

written commun., 2013) or from literature (Freeze and Cherry, 

1979, table 2.3) are used for hydraulic characteristics in this 

study. The DACAAR has been monitoring groundwater levels 

(depth to water) and specific conductance at well W5 (fig. 4; 

also known as DACAAR groundwater monitoring well 4) in 

Khurd Kabul village since 2005 (Danish Committee for Aid 

to Afghan Refugees, 2001). Historical streamflow measurements collected by the Afghanistan Ministry of Energy and 

Water (MEW) (Olson and Williams-Sether, 2010) were used 

to assess recharge to the Chakari Basin.

Water-Quality Data

The AGS engineers collected a variety of water samples 

that were shipped to the United States for analysis at several USGS laboratories. Water temperature, pH, and specific 

conductance were measured in the field and provided general information about basic properties. Major ion, nutrients, 

and trace elements were determined from filtered samples 

and provided information on general water chemistry. Water 

samples also were collected for total coliform and Escherichia

coli (E. coli) bacteria, which also are useful indicators of 

general water quality. Additional water samples for chemical 

and isotopic analysis were collected to provide supporting 

evidence of hydrogeologic processes, such as the time elapsed 

since recharge or the degree of evaporation of groundwater 

recharge. Generally, AGS engineers followed USGS procedures for the collection of water samples. In some cases, these 

procedures were modified to reflect challenging field conditions, such as the lack of ice to chill samples. Security issues 

greatly limited the time that project personnel could spend in 

the field, the locations they could access, and the number of 

samples that could be collected; therefore, the number and 

types of quality-control samples were limited. The lack of ice 

for sample preservation likely affected only the nutrient and 

carbon-14 samples. Thus, the nutrient values from this study 

are reported as estimated values because samples were not 
Introduction 7

69°20'E 69°25'E

34°25'N

34°20'N

EXPLANATION

Kareze path

Irrigated or cultivated area

Base from U.S. Geological Survey shuttle radar topography mission, 85-meter resolution, 2000

Universal Transverse Mercator projection, Zone 42 N, World Geodetic System, 1984 

Boundary of Chakari Basin—From Afghan 

 Information and Management Service (1997). 

 See figure 1 for full extent. 

Data collection site and identifier

Exploratory borehole (N5 identified only)

Kareze

Spring

Well, sampled as part of this study

Chakari River 

0 1 2 MILES

0 2 4 KILOMETERS

Perennial stream

Drainage network—Generated from 85-meter 

 digital elevation model data

Ephemeral stream

N5

K1

S1

W2

R1

Well, data provided by Danish Committee for 

 Aid to Afghan Refugees (DACAAR) (2011) (no identifier)

S1

N5

W2 S3

W1

K1

S2

W4

W3

W5

R1

W6

W8

W7

Band-i-Amin Ghazi 

Reservoir

Chakari River

Figure 4. Locations of wells, springs, karezes, and streams in the Chakari Basin sampling network, Afghanistan.
8 Hydrogeology and Water Quality of the Chakari Basin, Afghanistan

Table 2. Wells, kareze, springs, and stream sampled in the Chakari Basin, Afghanistan.

[W, S, K, and R in identifiers denote wells, springs, kareze, and the Chakari River site, respectively. Elevation refers to distance above the World Geodetic 

System of 1984 vertical datum and is from advanced spaceborne thermal emission and reflection radiometer (ASTER) global digital elevation model (U.S. 

Geological Survey, undated). m, meters; --, not applicable or not measured]

Identifier Location Elevation, 

in m Type Well depth measured, in m

Depth to water, 

in m

Measurement 

or sample date

W1 Taghar Sofla Mosque 2,135 Drilled well 55 14.70 23 Dec 2012

W2 Taghar Sofla School 2,144 Drilled well 41 22.79 24 Dec 2012

W3 Kharoti High School 2,141 Drilled well 30 -- 30 Dec 2012

W4 Aynak Mosque 2,093 Drilled well 37 4.07 01 Jan 2013

W5 Khurd Kabul 2,150 Dug well 40 37.80 02 Jan 2013

W6 Malang Pain 2,194 Drilled well 60 42.49 07 Jan 2013

W7 Dawran Khel 2,241 Drilled well 36 17.46 08 Jan 2013

W8 Shuman Zay Pine 2,206 Drilled well 51 21.00 14 Jan 2013

S1 Band Ghazi 2,060 Spring -- -- 22 Dec 2012

S2 Khurd Kabul 2,139 Spring -- -- 06 Jan 2013

S3 Band Ghazi 2,067 Spring -- -- 15 Jan 2013

S4 Band Ghazi (adjacent to S3) 2,067 Spring -- -- 19 Jan 2013

K1 Mirza Khan Kareze a

2,198 Kareze -- -- 25 Dec 2012

R1 Chakari River (also known as 

Malang Stream)

2,149 River -- -- 22 Jan 2013

a

Elevation is at outlet.

chilled and laboratory hold times were exceeded. The dissolved gas bottles remained sealed in transport and appeared 

to be well preserved, although denitrification (where available nitrate is converted to nitrogen gas) may have occurred. 

However, samples were collected during the winter with 

average daily temperatures of about zero degrees Celsius (°C) 

and stored in a cool location before shipping. Samples that 

required filtration and preservation were processed in the field 

at the time of sample collection. Water samples collected for 

the analysis of major ions, trace elements, tritium, helium, 

chlorofluorocarbons (CFCs), sulfur hexafluoride (SF6

), and 

oxygen and nitrogen isotopes were not affected by the lack of 

ice preservation. Bacteria samples were processed and incubated at the end of each field day.

The USGS National Water Quality Laboratory analyzed 

water samples for nutrients, major ions, and trace elements. 

The USGS Chlorofluorocarbon Laboratory analyzed sequential duplicate water samples for dissolved gases, CFCs 

[trichlorofluoromethane (CFC–11), dichlorodifluoromethane 

(CFC–12), and trichlorotrifluoroethane (CFC–113)], and 

SF6

. Dissolved gas concentrations of nitrogen, argon, carbon 

dioxide, and methane were analyzed by gas chromatography 

(U.S. Geological Survey, 2014b). CFC and SF6

 concentrations were analyzed by purge-and-trap gas chromatography 

(Busenberg and Plummer, 1992, 2000; International Atomic 

Energy Agency, 2006; U.S. Geological Survey, 2014a,c). The 

USGS Stable Isotope Laboratory analyzed water samples for 

nitrogen and oxygen isotopes in nitrate and deuterium and 

oxygen isotopes in water (U.S. Geological Survey, 2014d). 

Carbon isotopes (carbon 13 [13C] and carbon 14 [14C]) were 

determined at the National Ocean Sciences Accelerator Mass 

Spectrometry Facility (National Ocean Sciences, 2014). 

Water samples for tritium-to-helium (3

H:3He) age determination and noble gases helium, neon, argon, xenon, and krypton 

were collected in 80-centimeter (cm)-long copper tubes and 

analyzed at the Lamont-Doherty Earth Observatory Noble Gas 

Laboratory by mass-spectrometric procedures similar to those 

of Bayer and others (1989) and Beyerle and others (2000). All 

water quality, chemical, and isotopic analyses are provided in 

appendixes 1 through 3.

Hydrogeology

The hydrogeology of the Chakari Basin is interpreted 

using information from geologic maps and investigations, 

various satellite imagery, historical streamflow data, historical 

NGO well data, and chemical and isotopic analysis of 

water samples.
Hydrogeology 9

Surface Water

The Chakari River flows north through the Chakari Basin 

and drains into the Kabul River north of the study area (fig. 1). 

Figure 1 shows a drainage network generated from a digital 

elevation model that delineates several of the large ephemeral 

streams in the basin. The Chakari River drains to the Bandi-Amir Ghazi Reservoir above a stone dam at the northern 

end of the basin (coincident with the symbol for the historical 

Band-i-Amir Ghazi streamgage on fig. 1). The dam, which 

is 25 m high, was built in 1918 for irrigation, and the resulting reservoir had a capacity of 12 million cubic meters (m3

). 

The width of the reservoir across the valley is about 100 m at 

the top and 20 m at the bottom; however, the reservoir is now 

entirely filled in with sediment and is no longer effective for 

water storage.

The streamgage on the Chakari River at Band-i-Amir 

Ghazi (fig. 1, Afghan identification number 1–9.R00–4W) 

was operated by the MEW from May 26, 1965, through 

September 30, 1980. The mean annual streamflow for the 

period of record is 0.31 cubic meters per second (m3/s; 

26,784 m3/d), with a standard deviation of 0.12 m3/s (Olson 

and Williams-Sether, 2010). The mean annual precipitation 

at Kabul between 1957 and 1977 was 330 mm (Afghanistan 

Ministry of Water and Power, 1981). The mean annual 

streamflow per unit area for this streamgage is 8 × 10-4 cubic 

meters per second per square kilometer [(m3/s)/km2] or, 

expressed as a rate over the basin, 7 × 10-5 meters per day 

(m/d). The month with the highest mean monthly streamflow 

was May with 0.55 m3/s, and the month with the lowest mean 

monthly streamflow was January with 0.05 m3/s (fig. 2). The 

lowest monthly mean streamflow was 0.01 m3/s in January 

and February 1977 and March 1978. The Chakari River flows 

during December 2012 and January 2013 were observed 

to be small, likely much less than 0.5 m3/s. Mean monthly 

streamflow is lowest in the winter months when precipitation 

is highest (fig. 2). This indicates that a winter snowpack 

generally develops and that snow meltwater is likely the 

dominant contribution to spring and summer streamflows. 

Perennial streamflow in the basin, which is primarily only in 

the Chakari River, is likely a combination of snowmelt at high 

elevations at the southern areas of the basin (see cover figure) 

and drainage from the underlying bedrock aquifer in those 

areas. The ephemeral streams in the basin likely only flow in 

the spring or occasionally after precipitation events.

Springs are present in the study area, particularly at 

low elevations near the Band-i-Amir Ghazi Reservoir. Four 

springs and one kareze were inventoried for this study to help 

assess the source and movement of water in the Chakari Basin 

(table 2). During a field reconnaissance visit on November 21, 

2009—a relatively dry period—a spring was observed emanating from highly fractured gneiss on the north flank of the 

mountains bounding the study area. This spring, just outside 

the study area, provides insight into the nature of discharges 

from fractured bedrock in the area. The spring had a volumetrically measured flow of approximately 0.1 liter per second 

(L/s; 10-4 m3/s) near its source and was managed for irrigation, 

which is an indication of perennial flow. The spring was less 

than 1 km from the topographic peak in the local area and 

indicates groundwater draining from highly fractured bedrock 

uplands. On the eastern side of the study area, an ephemeral 

spring was identified on the flank of a south-facing gully near 

a ridge. The spring was about 0.7 km below a peak consisting of fractured carbonate rocks. The spring was not flowing 

when it was identified during the reconnaissance trip; however, there were small orchards at its origin and a settlement 

downgradient along the spring channel. Both factors indicate a 

likely dependence on easy access groundwater resources, such 

as would be provided by a shallow depth to groundwater, in 

the area of the spring. The springs observed in the study area 

generally coincide with delineated lineaments (Hubbard and 

others, 2012).

Geology

The geology of the study area is mapped in detail in 

Bohannon (2010). The Chakari Basin study area is within the 

Aynak Syncline Zone of the Kabul tectonic block, and detailed 

geologic and mineral investigations are provided by Peters 

and others (2011). The geologic units in the study area are 

categorized into hydrogeologic groups of similar hydrologic 

properties—primarily well yields and aquifer porosity—for 

the purposes of this study (fig. 5; table 3). The unconsolidated 

sediments are grouped according to sediment particle size, 

particle sorting, and deposition method, all of which can affect 

the hydrologic properties of the resulting deposits. Unconsolidated sediments and bedrock units were each grouped into 

four general hydrogeologic groups as shown in table 3.

Bedrock

Limestones and dolomites form the dominant bedrock 

outcrop in the study area particularly, the northeastern, 

northwestern, and the south-central part of the study area 

(fig. 5). Dolomitic marble is the primary host rock for the 

Aynak copper mineralization. Limestone and dolomite east 

of the Chakari River are in contact with sedimentary rocks 

(sandstone) along low-angle faults; sedimentary rocks may 

be present beneath unconsolidated sediments in much of the 

study area (Bohannon, 2010). Outcrops of metamorphic rock 

(gneiss and migmatite, amphibolite, schist, and marble) form 

the ridges along the northern boundary of the study area and 

form some of the ridges and hills within the basin (fig. 5). 

Erosion has exposed metamorphic rock in the upper reaches of 

the Chakari River. Intrusive igneous rocks in the study area are 

primarily in small areas near the northwestern corner of the 

study area, where they have intruded metamorphic rocks.
10 Hydrogeology and Water Quality of the Chakari Basin, Afghanistan

69°20'E 69°25'E

34°25'N

34°20'N

Hydrogeology modified

from Bohannon (2010)

EXPLANATION

(Map shades may be darker than shown because they are combined 

with the underlying digital elevation model base relief)

Hydrogeologic groups

Conglomerate sediments Intrusive igneous rocks

 and rocks

Sedimentary rocks

Limestones and dolostones

Metamorphic rocks

Lineaments

Faults River channel

Sands, undifferentiated

Loess and fine sediments

Water and lake sediments

Base from U.S. Geological Survey shuttle radar

topography mission, 2000, 85-meter resolution

Universal Transverse Mercator projection, 

Zone 42 N, World Geodetic System, 1984 0 1 2 MILES

0 2 4 KILOMETERS

Perennial stream

Drainage network—Generated from 85-meter 

 digital elevation model data

Ephemeral stream

Chakari River

Boundary of Chakari Basin—See 

 figure 1 for full extent

Band-i-Amin Ghazi 

Reservoir

Figure 5. Generalized geology and topography in the study area in the Chakari Basin, Afghanistan. Lineaments data are 

from Hubbard and others (2012).
Hydrogeology 11

Table 3. Hydrogeologic groups in the Chakari Basin, Afghanistan.

[Hydrogeologic groups are shown on figure 5. Geologic map units and unit codes (in parentheses) are from Bohannon (2010)]

Hydrogeologic group Relative well yield for 

sediments or rocks Geologic map unit

Sediments

River channel Very high Young alluvium (Qa3

)

Sands, undifferentiated High Colluvium and rock falls (Qcr), alluvial sheet deposits (Qas), intermediate 

alluvium (Qa2

), and older alluvium (Qa1)

Loess and fine sediments Moderate to high (where 

reworked)

Fine-grained deposits (Nlfw) and purple fine-grained facies (Nlfp)

Conglomerate sediments 

and rocks

Low to moderate Conglomerate (Nlc) (this unit is unconsolidated to semiconsolidated and is 

grouped with sediments for this study)

Rocks

Sedimentary rocks Moderate Undifferentiated unit ($Kku), conglomerate and sandstone unit (Pkc)

Limestones and dolostones Moderate to high where 

highly fractured

Belemnite unit (Jkb), undifferentiated limestone (Jku), Nerineen unit (Jkn), limestone, dolomite and tuff (^klt), Ceratiten unit (^kkc), reef limestone unit (Pkl), 

Gulkhamid Formation (_g), Gulkhamid and Loy Khwar Formations, undifferentiated (_Zu), Loy Khwar Formation (_Zlk)

Metamorphic rocks Very low to moderate 

where highly fractured

Light-blue unit ($Kklb), amphibolite (Zwa), undifferentiated (Zwu), gneiss and 

migmatite (Xsgn)

Intrusive igneous rocks Very low to moderate 

where highly fractured

Peridotite unit ($Kkp), brown peridotite unit ($Kkpb), mafic ring dike (_md), 

intrusions of Aynak district (_Zi), intrusive amphibolite (Zia)

The sedimentary, carbonate, and metamorphic rocks 

found in the study area generally are not considered to 

be primary aquifers because these rocks typically are low 

yielding. However, boreholes drilled for the North AynakTaghar mineral investigation (fig. 4) found the rock at the 

site, primarily limestone, to be highly fractured. The loss of 

considerable amounts of drilling fluid to the formations during 

drilling supports these findings. Although drillers logs did not 

have a record of the static water levels in the boreholes while 

drilling, the rocks contained water near the surface in places. 

A static water level of 7 m below land surface (corrected for 

borehole angle) was measured at borehole N5, which is about 

50 m vertically above the valley floor and 300 m horizontally 

from the valley (fig. 4). Mapped faults (Bohannon, 2010) 

and lineaments (Hubbard and others, 2012) also indicate that 

rocks in the study area are likely to be highly fractured and 

may contain considerable amounts of water. Where exposed 

at the surface, these rocks appear to be intensely fractured, 

and the intense fracturing likely results in moderate hydraulic 

conductivities and potential for groundwater storage. Watersupply wells constructed in the bedrock hydrogeologic groups 

could supply limited qualities of water, provided that there is 

sufficient recharge to replenish groundwater withdrawals. The 

fracture porosity, hydraulic conductivity, and storage in these 

aquifers likely diminishes with depth. Persistent spring and 

kareze flows in or near bedrock areas of the Chakari Basin 

indicate slow water drainage from underlying rock aquifers.

Unconsolidated Sediments

The distribution of the unconsolidated sediments in the 

study area results from the sequence of erosion and subsequent 

sedimentation that has occurred. The oldest unconsolidated 

sediments outcropping in the study area are conglomerate sediments and rocks; these deposits are exposed across the region 

and underlie most other basin-fill sediments in the study area 

(fig. 5). The stratigraphic sequence of the unconsolidated sediment hydrogeologic groups in the study area, from youngest 

to oldest, likely follows the order (from top to bottom) of the 

groups listed in table 3. There are no measured sections or 

borehole lithologic descriptions of the conglomerate sediments 

and rocks group but these deposits are probably similar to the 

upper Neogene conglomerates of the Kabul Basin (Mack and 

others, 2010), which are more permeable than the thick lower 

Neogene conglomerates found at depth in the Kabul Basin. 

The positions of the mapped outcrops indicate that a loess 

and fine sediments group probably overlies the conglomerate 

group. The loess and fine sand may be deposited directly on 

bedrock in some parts of the study area where the conglomerate was removed by erosion.

The oldest and intermediate alluvium of the undifferentiated sand group are the most extensive sediments mapped 

in the study area, followed by the colluvium, rock falls, and 

alluvial sheet deposits (Bohannon, 2010), which are also part 

of the undifferentiated sand group (table 3). The youngest 
12 Hydrogeology and Water Quality of the Chakari Basin, Afghanistan

sediments in the study area are the sediments of the river 

channel group (young alluvium), which are found along the 

Chakari River and the larger drainages in the study area. 

This group consists of coarse-grained sands and gravels that 

are likely to be highly permeable (fig. 6). The river channel 

hydrogeologic group was deposited in cut-and-fill channels 

and could be in depositional contact with older unconsolidated 

sediment of other hydrogeologic groups (fig. 5). Well yield 

tests in river channel sediments or river reworked loess or 

alluvium in the Kabul Basin less than 10 km northwest of the 

study area indicated aquifer materials yielding tens to hundreds of liters per minute. Where sediments are fine-grained 

loess or cemented conglomerates, yields were considerably 

lower (a few liters per minute or less).

Basin-Fill Aquifer Thickness

The primary source of water for domestic or industrial 

water use in the Chakari Basin is likely to be groundwater in 

the aquifer formed by the basin-fill unconsolidated sediments. 

The depths of drilled wells and limited passive seismic data 

were used to infer a minimum thickness of basin-fill unconsolidated sediments in the study area (fig. 7). In the center of 

the valley, along the Chakari River, well depths of 60 m are 

common, and one well is 94 m deep. Farther from the valley 

center, well depths indicate thicknesses of 40 to 60 m in most 

of the basin and thinner sediments near bedrock outcrops at 

the valley walls. The extent of mapped conglomerates also is 

shown on figure 7. The degree of consolidation of these sediments is not known, but these sediments are likely to have a 

porosity greater than that of the consolidated rock units and 

thus are included in the aquifer thicknesses shown (fig. 7). 

Depths to water range from 4 to 42 m below land surface, 

based on available data, (table 2), so the saturated thickness of 

the basin-fill aquifer is probably less than 100 m in all areas of 

the basin.

Water-Level Fluctuations

The monthly groundwater levels from 2004 to 2012 in 

well W5 (fig. 4) were assessed, using the seasonal Kendall 

test (Hirsch and Slack, 1984; Helsel and others, 2006), 

to determine whether trends were evident. A statistically 

significant slope (p value less than 0.05) in the relation of 

depth to water and time is considered evidence of a trend. No 

statistically significant trend in groundwater levels is apparent 

across the entire period of record; however, a break in slope is 

apparent in 2008. Examination of the water levels before and 

after September 2008 (selected as an approximate midpoint 

in the record) indicates that there was a slight but significant 

water-level rise of 0.02 meter per year (m/yr) between 2005 

and 2008 and no trend after 2008. This water-level rise may 

be attributed to the end of a multiyear drought in the region 

in 2005. A similar increasing trend in groundwater levels in 

the region before 2008 and a break in the slope of the trend 

in 2008 were observed in the adjacent Kabul Basin (Mack 

and others, 2010, 2013). The decreases in the groundwater 

level in the city of Kabul, however, are a result of increasing 

water use.

The groundwater level at well W5 did not have a consistent seasonal pattern, but some low levels occurred in late 

fall to winter and some high levels occurred in late spring 

(fig. 8). The median annual rainfall- or snowmelt-induced 

groundwater-level rise was 0.3 m. The mean annual precipitation for the period of record (2005–2012) at the Kabul airport 

was 335 mm (Afghanistan Agrometerological Project, 2013). 

A groundwater recharge rate of 0.07 m/yr (2 × 10-4 m/d) was 

estimated using the water-table fluctuation method (Healy and 

Cook, 2002), using a specific yield of 0.25 and a water-table 

rise of 0.3 m/yr. Ideally the water-table fluctuation method is 

used with continuous data so that all water-level rises in the 

time period for which the estimates are made are measured. 

The water-table fluctuation method as applied in the present 

study, using monthly water-level data, results in recharge estimates that are approximate, because not all water-level rises 

are captured with monthly measurements. However, a similar 

water-table fluctuation analysis, using monthly water-level 

measurements, in a closed basin in southern Australia (Ordens 

and others, 2012) yielded estimates of recharge that compared 

favorably with recharge estimates based on isotopic analysis.

The recharge estimated at well W5 in the Chakari Basin 

is a result of precipitation at the well and infiltration of 

streamflow from snowmelt in upland areas of the basin (fig. 4). 

The estimated recharge rate is about one order of magnitude 

greater than the historical rate of water leaving the basin (see 

“Surface Water” section). This indicates that the Chakari 

River likely represents a substantial source of recharge 

where it traverses from less permeable bedrock uplands to 

more permeable unconsolidated sediments. Chemical and 

isotopic results of surface and groundwater measurements, 

discussed in later sections, support a conceptual model that 

includes recharge of the basin-aquifer by streamflow lost 

from the snowmelt-supplied Chakari River. The Chakari 

Basin is essentially a closed basin, and the difference between 

the estimated groundwater recharge rate and the lower rate 

of discharge at the basin outlet indicates that there may be 

considerable water loss resulting from evapotranspiration in 

the lower areas of the basin, where irrigation is concentrated 

and the water table is near the land surface.

Groundwater Flow and Storage

A water-table map of the Chakari Basin is provided 

in figure 9, for the area of basin-fill sediments, showing 

generalized 50-m contours from 2,100 to 2,350 m. The 

water-table surface was contoured from the land-surface 

elevation minus the depth to water measured by the AGS in 

December 2012 and January 2013 at supply wells (table 2) 

or from historical static depth to water measured at the time 

of well construction (Danish Committee for Aid to Afghan 
Hydrogeology 13

A

B

Figure 6. Coarse-grained sediments in a stream channel on the west side of the Chakari Basin, Afghanistan, 

looking A, north and B, south.
14 Hydrogeology and Water Quality of the Chakari Basin, Afghanistan

69°20'E 69°25'E

34°25'N

34°20'N

Chakari River

Band-i-Amin Ghazi 

Reservoir

EXPLANATION

Boundary of Chakari Basin—See 

 figure 1 for full extent

Geology modified from Bohannon (2010)

Thickness of unconsolidated 

 sediments, in meters

Approximate area of unconsolidated 

 to semiconsolidated conglomerates

100

10

50

Base from U.S. Geological Survey shuttle radar

topography mission, 85-meter resolution, 2000

Universal Transverse Mercator projection, 

Zone 42 N, World Geodetic System, 1984 

Well depth, in meters below land 

 surface—DACAAR data (2011)

>10 to 30

>30 to 40

>40 to 60

>60 to 80

>80 to 94

0 1 2 MILES

0 2 4 KILOMETERS

Perennial stream

Drainage network—Generated from 85-meter 

 digital elevation model data

Ephemeral stream

Figure 7. The thickness of unconsolidated and semiconsolidated sediments in the Chakari Basin, Afghanistan.
Hydrogeology 15

B

Monthly precipitation, in millimeters

Month/Day/Year, Kabul, Afghanistan 

0

20

40

60

80

100

120

140

160

01/01/200301/01/200401/01/200501/01/200601/01/200701/01/200801/01/2009

01/01/2010

01/01/2011

01/01/2012

01/01/2013

36.8

37.0

37.2

37.4

37.6

37.8

Depth to water, in meters

Figure 8. Hydrograph of well W5 (Danish Committee for Aid to Afghan Refugees well GMW–4) in the Chakari Basin and 

total monthly precipitation in Kabul, Afghanistan, 2005 through 2011.

Refugees, 2010). For the 2012–2013 measurement points 

(eight wells and four springs), depth to water ranged from 

0 m at springs to 37.8 and 42.5 m at wells W5 and W6. The 

mean depth to water was 14 m. The mean depth to water at 

35 historical points was 22 m. A maximum depth to water of 

65 m was measured near well W6. The depth to water is 0 m at 

the Band-i Amir Ghazi Reservoir and assumed to be near 0 m 

at downstream reaches of the Chakari River.

The water table surface generally follows the land surface 

topography. Directions of groundwater flow are toward the 

center of the basin and northward toward the Band-i Amir 

Ghazi Reservoir. The greatest inflows to the unconsolidated 

aquifer are likely to occur primarily where the Chakari River 

loses water as it enters areas underlain by the unconsolidated 

aquifer (fig. 7) and secondarily where other ephemeral 

drainages enter areas underlain by the unconsolidated aquifer. 

Groundwater in the study area ultimately discharges to the 

Chakari River or its tributary drainages and the Band-i Amir 

Ghazi Reservoir. Water-table contours are widely spaced in 

the center of the basin where gradients are low. Gradients 

may be steeper in the bedrock of the surrounding hillsides, 

following the topography. However, the nature of the gradients 

is generally unknown in the bedrock, because water level 

data are available only from one borehole. In borehole N5, 

about 330 m east of and 30 m higher than the reservoir, the 

depth to water was measured to be 7 m below land surface 

(January 2013).

In a subbasin of the Kabul Basin, isotopic evidence 

indicated that there was regional interbasin groundwater 

flow across a surface-water divide into the Kabul Basin from 

an adjacent high-elevation basin (Mack and others, 2010). 

Similarly, there could be regional groundwater flow from 

the Chakari Basin to the lower elevation Kabul Basin (to the 

northwest) or to the Logar Basin (to the west) through the 

bedrock ridges that delineate the basins (fig. 1); the Kabul 

and Logar Basins are about 300 m lower in elevation than 

the Chakari Basin. It is not likely that there is interbasin 

groundwater flow to or from the basin to the east of the 

Chakari Basin (figs. 7 and 9) because the basins have similar 

elevations and there is a topographic divide between them.

Groundwater storage in the basin is expected to 

be greatest in the unconsolidated sediments and the 

unconsolidated to semiconsolidated conglomerates (fig. 7). 

In the lower elevation areas of the northern Chakari Basin, 

these sediments cover areas of approximately 120 and 30 km2, 

respectively. Assuming an average porosity of 0.20 and an 

average saturated thickness of about 20 m, the volume of 

groundwater stored in these sediments would be at least 

600 million cubic meters. As in any aquifer system, not all 

groundwater can be physically extracted, and the stored 

volume is much greater than the recharge (26,784 m3/d based 

on average annual streamflow) that sustains groundwater in 

the basin. Groundwater in storage provides some buffer to 

the seasonal climatic variability of water resources; however, 

new or increased groundwater withdrawals must be carefully 

assessed to avoid negatively affecting existing, generally 

shallow water resources. Additionally, because recharge in the 

basin is supplied by a melting winter snowpack in the spring 
16 Hydrogeology and Water Quality of the Chakari Basin, Afghanistan

2,200

2,200

2,250

2,250

2,200

2,150

2,100

2,200

2,150

2,350

2,300

2,250

2,200

2,300

69°20'E 69°25'E

34°25'N

34°20'N

EXPLANATION

Water-measurement site

Direction of groundwater flow

Boundary of Chakari Basin—See 

 figure 1 for full extent Kareze

Spring

Well, measured as part of this study

Exploratory borehole 

Well, data from Danish Committee for

 Aid to Afghan Refugees (2011)

0 1 2 MILES

0 2 4 KILOMETERS

Perennial stream

Drainage network—Generated from 85-meter 

 digital elevation model data

Ephemeral stream

Water-table contour—Shows approximate 

 altitude of water-table. Contour interval 

 is 50 meters. Datum is World Geodetic System, 1984

Chakari River

Base from U.S. Geological Survey shuttle radar topography mission, 85-meter resolution, 2000

Universal Transverse Mercator projection, Zone 42 N, World Geodetic System, 1984 

Band-i-Amin Ghazi Reservoir

Figure 9. Water-table elevation and direction of groundwater flow in the Chakari Basin, Afghanistan.
Water Quality, Chemistry, and Isotopes 17

and summer, the availability of water resources is likely to 

be affected by climate changes. An integrated assessment, 

using a groundwater flow model, of the variables involved 

in estimating groundwater availability and sustainability—

including the physical geometry of an aquifer system, the 

hydraulic characteristics of the sediments (porosity and 

hydraulic conductivity), and the amount and timing of inflows 

and outflows (recharge and discharges)—would improve 

understanding of the aquifer system.

Water Quality, Chemistry, and Isotopes

Water quality samples were collected in the Chakari 

Basin during December 2012 and January 2013 from the 

Chakari River, eight wells, four springs, and one kareze (fig. 4; 

table 2; appendixes 1–3). Samples collected from the springs 

and kareze represent discharging groundwater and are considered groundwater for purposes of this study. Water quality 

in the sparsely populated Chakari Basin is generally good 

with dissolved solids less than 600 mg/L, although elevated 

nitrogen compounds were detected in some of the samples 

(table 4).

Surface Water

One surface-water sample was collected from the 

Chakari River in January 2013. The surface water sample had 

a specific conductance of 228 microsiemens per centimeter 

at 25 degrees Celsius (μS/cm at 25 °C), a concentration of 

dissolved solids (DS; defined as the amount of dried solids 

at 180 °C) of 250 milligrams per liter (mg/L), and a field pH 

measurement of 7.9 (appendix 1). Concentrations of nutrients 

and major ions in the Chakari River sample were similar to 

concentrations in other upland rivers flowing into the Kabul 

Basin, such as the Paghman and Istalef Rivers (Mack and 

others, 2010) but had higher alkalinity and concentrations of 

calcium, magnesium, sulfate, and strontium, reflecting the 

limestone, dolostone, and gypsum found in the Chakari Basin. 

The concentration of copper (8.4 micrograms per liter [μg/L]) 

in the Chakari River sample was about an order of magnitude higher than concentrations in other rivers in the Kabul 

Basin (Mack and others, 2010). The concentration of cobalt 

(1.49 μg/L) in the Chakari River sample was similar to concentrations in the Logar River (just west of the Chakari Basin), 

but 5 to 10 times higher than concentrations in the Paghman 

and Istalef Rivers (Mack and others, 2010). Concentrations of 

copper and cobalt in the Chakari River reflect the presence of 

mineral-rich deposits in the Chakari Basin.

Groundwater

Groundwater samples from the Chakari Basin were 

collected from relatively shallow sources (four springs, one 

kareze, and eight wells ranging in depth from approximately 

30 to 90 m in unconsolidated sediments). Samples were 

collected from sources either at the water table (kareze and 

springs) or, with the exception of well W1 (40 m below the 

water table), from less than 20 m below the water table. There 

were no clear differences in the major ion chemistry between 

wells and springs. This is expected because the springs and 

the kareze are supplied by groundwater discharge. The kareze 

generally had lower concentrations of major ions than wells or 

springs, but similar proportions of major ions. Field specific 

conductance measurements in 13 groundwater samples ranged 

from 438 to 970 μS/cm at 25 °C and had a median value of 

621 μS/cm at 25 °C (fig. 10); the median pH was 7.7, and the 

median value of alkalinity was 221 mg/L as calcium carbonate (CaCO3

) (table 4). These conductivities, pH values, and 

alkalinities were similar to values in other sparsely populated 

areas in the upper reaches of the Kabul, Istalef, Panjshir, and 

Paghman valleys (Mack and others, 2010). DS in groundwater 

samples ranged from 242 to 578 mg/L and had a median value 

of 365 mg/L (fig. 11; table 4). DS in one well (W7) exceeded 

the recommended guideline of 500 mg/L that was established by the U.S. Environmental Protection Agency (EPA) 

for public water supplies in the United States (table 4). The 

highest conductivities and DS concentrations were measured 

in samples from wells W7 and W5, which are in areas with 

a relatively greater population density than elsewhere in the 

basin (fig. 3). The hardness of the 13 groundwater samples 

(which is primarily due to calcium and magnesium dissolved 

in the water) ranged from 208 to 344 mg/L as CaCO3. Based 

on the hardness scale that characterizes water from soft to very 

hard (Hem, 1992), all the groundwater samples from this study 

indicate that the water is very hard (hardness greater than 

180 mg/L as CaCO3).

Where DS concentrations were high, concentrations 

of sodium, chloride, and sulfate also were high. Major ion 

chemistry was dominated by calcium-bicarbonate type waters, 

with a few magnesium-bicarbonate water types and one 

sodium-bicarbonate-sulfate water type. Calcium-bicarbonate 

major ion chemistry also was dominant in other subbasins 

around the Kabul Basin (Broshears and others, 2005; Mack 

and others, 2010). Changes in the major ion chemistry from 

calcium-magnesium-bicarbonate to sodium-bicarbonatesulfate water types may be attributable to the weathering of 

rock that contains gypsum (Broshears and others, 2005).

Mass-Concentration Ratios

The ratios of select ions to chloride, a conservative tracer, 

were compared between surface-water and groundwater 

samples to help determine if there are interactions between 

the water and rock. Similar ratios of sodium to chloride in 

surface water and groundwater in the Chakari Basin suggest a common source but little or no reaction between water 

and rock involving sodium. Ratios of calcium, magnesium, 

sulfate, and to a lesser extent silica, potassium, strontium, 

and arsenic relative to chloride were higher in surface water 

than in groundwater, indicating that interactions between 
18 Hydrogeology and Water Quality of the Chakari Basin, Afghanistan Table 4. Summary statistics for selected physical properties, inorganic water-quality constituents, and raw and modeled isotopes in groundwater samples collected by the Afghanistan Geological Survey from eight wells, four springs, and one kareze in Chakari Basin, Afghanistan, 2012–2013.—Continued [MRL, minimum reporting limit; Min, minimum; Max, maximum; WHO, World Health Organization; EPA, U.S. Environmental Protection Agency; μS/cm at 25 °C, microsiemens per centimeter at 25 degrees Celsius; na, no value or not applicable; °C, degrees Celsius; mg/L, milligrams per liter; <, less than; e, estimated; μg/L, micrograms per liter; per mil, parts per thousand; TU, tritium units] Water-quality properties and constituents Units Num- ber of samples Common MRL Percentage of samples above MRL Concentration WHO drinking- water standard EPA drinking- water standard Min Quartile Max 25th 50th 75th Physical properties pH, field Standard units 13 na 100 7.5 7.6 7.7 7.8 8.0 na a6.5–8.5 pH, laboratory Standard units 13 na 100 7.7 7.9 8.0 8.1 8.2 na na Specific conductance, field μS/cm at 25 °C 13 na 100 438 566 621 684 970 na na Specific conductance, laboratory μS/cm at 25 °C 13 na 100 432 562 628 686 979 na na Water temperature °C 13 na 100 10.8 12.2 13.9 14.3 15.5 na na Major ions Total dissolved solids, summed (as DS) mg/L 13 10 100 249 332 365 427 578 na a500 Hardness, dissolved, calculated (as CaCO3

)

mg/L 13 na 100 208 225 244 295 344 na na

Calcium, dissolved (as Ca) mg/L 13 0.04 100 34.6 45.7 47.5 66.5 81.6 na na

Magnesium, dissolved (as Mg) mg/L 13 0.02 100 22.5 28 29.7 33.3 38.2 na na

Potassium, dissolved (as K) mg/L 13 0.06 100 1.38 2.06 3.30 5.28 8.47 na naSodium, dissolved (as Na) mg/L 13 0.1 100 8.08 23.5 36.6 49.8 109 na b30–60

Alkalinity, dissolved, field (as CaCO3

) mg/L 13 na 100 163 194 221 228 250 na na

Bicarbonate, dissolved, field (as HCO3

) mg/L 13 na 100 189 232 267 276 304 na na

Carbonate, dissolved, field (as CO3

) mg/L 13 0.1 61 <0.1 <0.1 <0.1 1 2 na na

Bromide, dissolved (as Br) mg/L 13 0.01 100 0.032 0.069 0.123 0.162 0.429 na na

Chloride, dissolved (as Cl) mg/L 13 0.12 100 5.40 11.0 16.2 26.2 105 na a250

Fluoride, dissolved (as F) mg/L 13 0.1 100 0.19 0.32 0.35 0.38 0.55 1.5 2–4

Silica, dissolved (as SiO2

) mg/L 13 0.06 100 10.7 13.6 17.0 18.3 20 na na

Sulfate, dissolved (as SO4

) mg/L 13 0.18 100 22.7 58.9 67.7 87.4 156 na b250

Nutrients

Nitrogen, ammonia, dissolved (as N) mg/L 13 0.001 38 <0.0001 <0.0001 <0.0001 e0.019 e0.3 na b30

Nitrogen, nitrite plus nitrate, dissolved 

(as N)

mg/L 13 0.001 100 e0.21 e2.6 e3.1 e4.1 e12.9 c10 10

Phosphorus, orthophosphate, dissolved 

(as P)

mg/L 13 0.001 31 <0.0001 <0.0001 <0.0001 e0.003 e0.033 na na
Water Quality, Chemistry, and Isotopes 19

Table 4. Summary statistics for selected physical properties, inorganic water-quality constituents, and raw and modeled isotopes in groundwater samples collected by the Afghanistan Geological Survey from eight wells, four springs, and one kareze in Chakari Basin, Afghanistan, 2012–2013.—Continued[MRL, minimum reporting limit; Min, minimum; Max, maximum; WHO, World Health Organization; EPA, U.S. Environmental Protection Agency; μS/cm at 25 °C, microsiemens per centimeter at 25 degrees Celsius; na, no value or not applicable; °C, degrees Celsius; mg/L, milligrams per liter; <, less than; e, estimated; μg/L, micrograms per liter; per mil, parts per thousand; TU, tritium units]

Water-quality properties 

and constituents Units

Number of 

samples

Common 

MRL

Percentage 

of samples 

above MRL

Concentration WHO 

drinkingwater 

standard

EPA 

drinkingwater 

standard

Min

Quartile

Max

25th 50th 75th

Dissolved gases

Carbon dioxide (as CO2) mg/L 13 na 100 3.6 9.5 10.8 17.2 21.9 na na

Nitrogen (as N2 ) mg/L 13 na 100 12.7 13.3 14.3 14.5 19.1 na na

Argon (as Ar) mg/L 13 na 100 0.47 0.49 0.51 0.52 0.6 na na

Methane (as CH4) mg/L 13 0.001 23 <0.001 <0.001 <0.001 <0.001 0.1 na na

Trace elements

Aluminum, dissolved (as Al) μg/L 13 2.2 77 <2.2 2.4 3.3 3.7 13.7 na a50–200

Antimony, dissolved (as Sb) μg/L 13 0.027 85 <0.027 0.03 0.05 0.07 0.38 na 6

Arsenic, dissolved (as As) μg/L 13 0.04 100 0.12 0.30 0.43 0.67 1.9 10 10

Barium, dissolved (as Ba) μg/L 13 0.1 100 31.2 38.2 46.8 49.0 65.0 700 2,000

Beryllium, dissolved (as Be) μg/L 13 0.006 23 <0.006 <0.006 <0.006 <0.006 0.01 na 4

Bismuth, dissolved (as Bi) μg/L 13 0.1 8 <0.1 <0.1 <0.1 <0.1 0.83 na na

Boron, dissolved (as B) μg/L 13 3 100 45 66 128 183 292 2,400 a6,000

Cadmium, dissolved (as Cd) μg/L 13 0.016 62 <0.016 <0.016 0.019 0.027 0.059 3 5

Cerium, dissolved (as Ce) μg/L 13 0.1 8 <0.1 <0.1 <0.1 <0.1 0.13 na na

Cesium, dissolved (as Cs) μg/L 13 0.1 15 <0.1 <0.1 <0.1 <0.1 0.70 na na

Chromium, dissolved (as Cr) μg/L 13 0.07 92 <0.07 0.73 1.2 1.4 2.2 50 100

Cobalt, dissolved (as Co) μg/L 13 0.023 100 0.047 0.067 0.105 0.195 1.94 na na

Copper, dissolved (as Cu) μg/L 13 0.8 100 1.0 11 17 29 77 2,000 a1,000

Gallium, dissolved (as Ga) μg/L 13 0.1 100 2.31 2.79 3.38 3.73 4.74 na na

Iodine, dissolved (as I) μg/L 13 0.1 100 3.4 7 14 17 32 na na

Iron (total), dissolved (as Fe) μg/L 13 4 77 <4 5 9 22 111 na a300

Lead, dissolved (as Pb) μg/L 13 0.025 69 <0.025 <0.025 0.06 0.15 0.69 na 15Lithium, dissolved (as Li) μg/L 13 0.22 100 4.47 6.30 8.86 10.3 16.2 na na

Manganese, dissolved (as Mn) μg/L 13 0.15 100 0.15 1.2 2.73 4.75 31.2 na a50

Molybdenum, dissolved (as Mo) μg/L 13 0.014 100 1.12 1.99 3.09 4.15 5.27 na a200Nickel, dissolved (as Ni) μg/L 13 0.09 100 0.24 0.29 0.41 0.62 9.1 na a100Neodymium, dissolved (as Nd) μg/L 13 0.1 8 <0.1 <0.1 <0.1 <0.1 0.1 na na
20 Hydrogeology and Water Quality of the Chakari Basin, Afghanistan Table 4. Summary statistics for selected physical properties, inorganic water-quality constituents, and raw and modeled isotopes in groundwater samples collected by the Afghanistan Geological Survey from eight wells, four springs, and one kareze in Chakari Basin, Afghanistan, 2012–2013.—Continued [MRL, minimum reporting limit; Min, minimum; Max, maximum; WHO, World Health Organization; EPA, U.S. Environmental Protection Agency; μS/cm at 25 °C, microsiemens per centimeter at 25 degrees Celsius; na, no value or not applicable; °C, degrees Celsius; mg/L, milligrams per liter; <, less than; e, estimated; μg/L, micrograms per liter; per mil, parts per thousand; TU, tritium units] Water-quality properties and constituents Units Num- ber of samples Common MRL Percentage of samples above MRL Concentration WHO drinking- water standard EPA drinking- water standard Min Quartile Max 25th 50th 75th Trace elements—Continued Rubidium, dissolved (as Rb) μg/L 13 0.1 100 0.18 0.28 0.72 1.9 6.5 na na Selenium, dissolved (as Se) μg/L 13 0.03 100 0.12 1.3 1.8 2.0 2.9 40 50 Silver, dissolved (as Ag) μg/L 13 0.005 15 <0.005 <0.005 <0.005 <0.005 0.007 na a100 Strontium, dissolved (as Sr) μg/L 13 0.2 100 364 790 951 1,100 1,440 na na Tellurium, dissolved (as Te) μg/L 13 0.1 100 0.45 0.54 0.63 0.67 0.85 na na Thorium, dissolved (asTh) μg/L 13 0.1 31 <0.1 <0.1 <0.1 0.37 1.7 na na Tin, dissolved (as Sn) μg/L 13 0.1 38 <0.1 <0.1 <0.1 0.25 1.0 na na Titanium, dissolved (as Ti) μg/L 13 0.1 100 0.44 0.55 0.66 0.77 1.5 na na Uranium, natural, dissolved (as U) μg/L 13 0.04 100 0.47 3.7 5.3 8.9 14 30 30 Vanadium, dissolved (as V) μg/L 13 0.08 100 0.39 1.1 3.1 4.5 14.2 na na Zinc, dissolved (as Zn) μg/L 13 1.4 69 <1.4 <1.4 22.3 66.3 189 na a5,000 Isotopes

CFC–11 modeled years Years 13 na 100 13.75 27.7 28.5 29.5 49.9 na na

CFC–12 modeled years Years 13 na 100 9.9 10.65 21.2 23.3 41.9 na na

CFC–113 modeled years Years 13 na 100 23.2 24.2 25 25.3 39.4 na na

Deuterium (2H) in water × 1,000 Ratio of 2H/1H, 

per mil

13 na 100 -66 -56.4 -55.3 -53.8 -52.8 na na

Deuterium excess × 1,000 Unitless 13 na 100 11.44 13.02 13.92 15.34 16.2 na na

delta 18O in water × 1,000 Ratio of 18O/16O, 

per mil

13 na 100 -10.06 -8.8 -8.63 -8.53 -8.18 na na

delta 18O in nitrate × 1,000 Ratio of 18O/16O, 

per mil

13 na 100 1.32 2.14 2.75 3.29 3.98 na na

delta 15N in nitrate × 1,000 Ratio of 15N/14N, 

per mil

13 na 100 4.03 6.27 6.96 7.31 10.24 na na

SF–6 modeled years Years 13 na 100 3.74 6.5 7.5 19.5 31.3 na na

14C, percent modern Percent 13 na 100 31.9 73.6 83.4 86.8 94.8 na na

Tritium (3H) TU 13 na 100 -0.01 2.2 6.7 8.6 9.7 na na

aNonenforceable lifetime health advisory or secondary drinking-water standard.bNonenforceable taste threshold.cThe WHO defines the maximum permissible concentration of nitrate in drinking water as 50 mg/L, which is equivalent to 10 mg/L as nitrogen.
Water Quality, Chemistry, and Isotopes 21

Band-i-Amin Ghazi Reservoir

69°20'E 69°25'E

34°25'N

34°20'N

S3 S4

K1

S1

S2

W1

W2

W3

W4

W5

W6

W7

W8

R1

EXPLANATION

Field specific conductance, in microsiemens per centimeter 

 at 25 degrees Celsius—K, kareze; S, spring; R, river; W, well;

 >, greater than

228 to 525

>525 to 650

>650 to 750

>750 to 850

>850 to 1000

0 1 2 MILES

0 2 4 KILOMETERS

Boundary of Chakari Basin—See 

 figure 1 for full extent

Perennial stream

Drainage network—Generated from 85-meter 

 digital elevation model data

Ephemeral stream

Base from U.S. Geological Survey shuttle radar topography mission, 85-meter resolution, 2000

Universal Transverse Mercator projection, Zone 42 N, World Geodetic System, 1984 

Chakari River

Figure 10. Specific conductance of water in the Chakari Basin, Afghanistan, 2012–2013.
22 Hydrogeology and Water Quality of the Chakari Basin, Afghanistan

S3 S4

K1

S1

S2

W1

W2

W3

W4

W5

W6

W7

W8

R1

69°20'E 69°25'E

34°25'N

34°20'N

EXPLANATION

Dissolved solids, in milligrams per 

 liter—K, kareze; S, spring; R, river; W, well;

 >, greater than

249 to 275

>275 to 300

>300 to 350

>350 to 450

>450 to 578

0 1 2 MILES

0 2 4 KILOMETERS

Boundary of Chakari Basin—See 

 figure 1 for full extent

Perennial stream

Drainage network—Generated from 85-meter 

 digital elevation model data

Ephemeral stream

Base from U.S. Geological Survey shuttle radar topography mission, 85-meter resolution, 2000

Universal Transverse Mercator projection, Zone 42 N, World Geodetic System, 1984 

Chakari River

Band-i-Amin Ghazi Reservoir

Figure 11. Dissolved solids concentrations in water in the Chakari Basin, Afghanistan, 2012–2013.
Water Quality, Chemistry, and Isotopes 23

water and rock, including calcite and gypsum precipitation 

and cation exchange, may be occurring in shallow groundwater. Arsenic, if available for mobilization, may be partially 

removed from groundwater, possibly through adsorption on 

iron-manganese oxyhydroxides. Solute concentrations in the 

Chakari Basin groundwater samples were generally about 

one order of magnitude greater than the concentration in the 

surface-water sample from the Chakari River. The low solute 

concentration of surface water indicates that the Chakari River 

probably loses water rather than gains discharged groundwater 

(which would have a relatively high solute concentration) as 

it traverses unconsolidated aquifer sediments. The enrichment 

of dissolved ions in groundwater compared to surface water in 

the Chakari Basin is relatively low compared with the enrichment of as much as two orders of magnitude that is found in 

other subbasins of the Kabul Basin (Mack and others, 2010).

Nutrients

Concentrations of nitrogen and phosphorous species 

were highest in two springs (S3, S4) near the mouth of the 

watershed and in one well (W5) along the Chakari River in an 

area of relatively high population (figs. 3 and 4; appendix 1). 

Estimated concentrations of nitrate plus nitrite—collectively 

referred to as nitrate in this report—ranged from 0.21 to 

12.9 mg/L as nitrogen (N) in 13 groundwater samples. 

The estimated median nitrate concentration of 3.1 mg/L 

as N was similar or slightly higher than the median nitrate 

concentration in other subbasins (1.2 to 3.8 mg/L as N) of the 

Kabul Basin (Mack and others, 2010). Nitrate concentrations 

in groundwater samples from the Chakari Basin also were 

similar to background concentrations observed in the arid 

southwestern United States (Anning and others, 2012). 

The concentration of one sample from well W5 (12.9 mg/L 

as nitrate; fig. 12; appendix 1) exceeded the World Health 

Organization’s (WHO; 2011) maximum permissible limit 

of 10 mg/L for nitrate as N (table 4). The low nitrate 

concentration (0.21 mg/L as N) in the groundwater sample 

from well W8 most likely is due to the fact that the sample 

contains a large fraction of old water (see “Hydrogen and 

Oxygen Isotopes of Water” section).

Bacteria

Coliform bacteria are found in soil, surface water, plants 

and in the intestines of animals and humans. The presence of 

coliform bacteria in groundwater indicates poorly constructed, 

cracked or unsealed wells. E. coli is a type of fecal coliform 

bacteria commonly found in intestines of animals and humans. 

E. coli bacteria were not detected in any samples, reflecting 

the relatively sparse population in the Chakari Basin. Total 

coliform bacteria were detected in three out of the four spring 

samples and in one water sample from well W5 (appendix 1). 

Livestock graze in the lowland areas near the springs. As 

reported earlier, well W5, a dug well, also had a nitrate 

concentration of 12.9 mg/L as N, indicating contamination 

from anthropogenic sources and possibly a poor well seal 

(fig. 12).

Oxidation-Reduction Conditions

Oxic conditions (where dissolved oxygen concentrations 

exceed 1 mg/L) are often found in shallow groundwater in 

areas with dry climates (Ayotte and others, 2011; Anning and 

others, 2012). Water-quality constituents that are sensitive 

to reduction and oxidation (redox) conditions, such as 

nitrogen species, iron, and manganese, provided evidence 

of oxic conditions in groundwater in the Chakari Basin 

(appendixes 1 and 2). Most of the nitrogen (estimated to be 

89 to 100 percent) was present as nitrate, the most oxidized 

form of nitrogen. Low concentrations of iron (median of 

8.9 μg/L) and manganese (median of 2.7 μg/L) in groundwater 

further indicated oxic conditions because these elements are 

less soluble under oxidizing conditions than under reducing 

conditions. The highest concentrations of iron (111 μg/L) 

and manganese (31.2 μg/L) and the lowest concentrations 

of nitrate (0.21 mg/L as N) were found at well W8. The 

large fraction of old water at well W8 indicates a longer 

and (or) a slower flow path compared with other sites in the 

basin. A longer flow path would allow for more time for 

interaction between water and rock, which in turn promotes 

the consumption of dissolved oxygen, leading to less oxidized 

groundwater conditions.

Trace Elements

Concentrations of many trace elements in groundwater 

of the Chakari Basin reflect the mineralized geology and 

the dry climate of the area (appendix 2). However, none of 

the trace element concentrations exceeded a WHO or EPA 

human-health benchmark or nonhealth guideline (table 4). 

High concentrations of boron (greater than 50 μg/L), selenium 

(greater than 1 μg/L), strontium (greater than 500 μg/L), 

and uranium (greater than 3 μg/L) in most samples from the 

Chakari Basin are typical of groundwater in unconsolidated 

sand aquifers under dry, oxic conditions and slightly alkaline 

pH (Ayotte and others, 2011). Concentrations of boron, 

selenium, strontium, and uranium in the groundwater samples 

from the Chakari Basin were similar to concentrations in other 

subbasins around the Kabul Basin (Mack and others, 2010) 

and were about twice as high as concentrations in groundwater 

samples in unconsolidated sand and gravel aquifers in arid 

regions of the United States (Ayotte and others, 2011). Zinc 

and copper concentrations in the groundwater samples 

from the Chakari Basin were 5 to 10 times higher than 

concentrations in groundwater samples from subbasins in the 

Kabul Basin (Mack and others, 2010) or in similar western 

regions of the United States (Ayotte and others, 2011). High 

concentrations of zinc and copper in groundwater samples 

from the Chakari Basin likely reflect the presence of dolomitic 
24 Hydrogeology and Water Quality of the Chakari Basin, Afghanistan

S3 S4

K1

S1

S2

W1

W2

W3

W4

W5

W6

W7

W8

R1

69°20'E 69°25'E

34°25'N

34°20'N

EXPLANATION

Nitrate plus nitrite, in milligrams per liter 

 as nitrogen—K, kareze; S, spring; R, river; W, well

0.21

1.9 to 2.6

2.7 to 4.1

4.2 to 5.4

12.9

0 1 MILES 2

0 2 4 KILOMETERS

Boundary of Chakari Basin—See 

 figure 1 for full extent

Perennial stream

Drainage network—Generated from 85-meter 

 digital elevation model data

Ephemeral stream

Base from U.S. Geological Survey shuttle radar topography mission, 85-meter resolution, 2000

Universal Transverse Mercator projection, Zone 42 N, World Geodetic System, 1984 

Band-i-Amin Ghazi 

Reservoir

Chakari River

Figure 12. Nitrate plus nitrite concentrations in water in the Chakari Basin, Afghanistan, 2012–2013. 
Water Quality, Chemistry, and Isotopes 25

marble (a metasedimentary rock) in the mineral-rich area 

(fig. 5; Peters and others, 2011; K.M. Renaud, W.R. Stettner, 

and S.G. Peters, written commun., 2014).

The trace-element concentrations in samples from the 

four springs and one kareze in the Chakari Basin were similar 

to concentrations in groundwater except for the concentrations 

of zinc. Concentrations of zinc in the springs (less than 1.4 to 

4.5 μg/L), the kareze (less than 1.4 μg/L), and surface water 

(1.6 μg/L) were relatively low compared with concentrations 

in well water (20 to 189 μg/L; appendix 2). Many of the highest trace element concentrations in the water samples from the 

Chakari Basin were from well W1 and springs S1, S3, and S4 

along the northern edge of the valley floor (fig. 4). Well W1 

had the highest concentrations of aluminum, boron, cobalt, 

iodine, antimony, titanium, and uranium. Spring S1 had the 

highest concentrations of copper, cadmium, and molybdenum, 

whereas springs S3 and S4 had the highest concentrations of 

arsenic, bismuth, and lithium. Farther from the northern ridge 

but near limestone and dolostone hills (fig. 5), well W4 had 

the highest concentrations of nickel and zinc. The proximity of 

wells W1 and W4 and springs S1, S3, and S4 to the mineralrich surrounding hills and ridges probably explains the 

relatively high concentrations of some of these trace elements 

compared with concentrations in samples from other wells and 

springs at greater distances from the mineral deposits.

Inorganic and Anthropogenic Tracer 

Constituents

Inorganic and anthropogenic tracers provide information on the apparent source and age of groundwater and 

processes affecting groundwater composition. However, these 

tracer-derived ages are considered “apparent” ages because a 

single water sample from a well or spring can be a mixture of 

groundwaters with different ages (appendix 3).

Nitrogen and Oxygen Isotopes of Nitrate

The isotopic compositions of nitrogen (δ15N) and oxygen 

(δ18O) in nitrate often are useful for determining sources 

of nitrate in groundwater and surface water (Kendall and 

Aravena, 2000). Different sources of nitrate have characteristic 

isotopic signatures (15N relative to 14N, expressed as δ15N). 

Isotope ratios are expressed as the ratio of the heavier isotope 

to the lighter isotope relative to the standard (nitrogen in air 

for δ15N) and are in parts per thousand (per mil). Sources from 

atmospheric nitrogen have δ15N ratios that are near zero as 

defined by their reference to atmospheric N2

. The δ18O ratios 

of soil nitrate formed from in situ nitrification of ammonium 

typically range from –10 to +10 per mil. Commercial 

fertilizers and vascular plants have δ15N ratios in the range 

of –4 to +4 per mil because they have an atmospheric source 

of nitrogen. Commercial fertilizers and desert areas with 

high-nitrate sediments may have δ18O ratios of nitrate in the 

range of +18 to +26 per mil. Natural soil organic matter has 

δ15N values that range from +3 to +9 per mil. δ15N ratios from 

human and animal wastes range widely, typically around +8 to 

+22 per mil (Böhlke, 2002).

δ18O ratios of nitrate in the 13 groundwater samples 

ranged from +1.32 to +3.98 per mil, and δ15N ratios of nitrate 

in 12 of the 13 groundwater samples ranged from +4.0 to 

+9.3 per mil, indicating organic soil matter as the predominant nitrogen source (fig. 13; table 4). The one exception 

Delta oxygen−18 of 

Nitrate, in parts per thousand

Delta nitrogen–15 of nitrate, in parts per thousand

Nitrate from ammonium 

fertilizers and precipitation

Soil nitrate

Biogenic nitrate (human

and (or) animal waste) EXPLANATION

0

2

4

6

0 5 10 15

River site

Isotope range

Spring

Kareze

Well, sampled as part

 of this study

Isotope ranges modified from Kendal and Aravena (2000) 

Figure 13. The isotopic composition of the nitrate in water samples from the Chakari Basin, 2012–2013.
26 Hydrogeology and Water Quality of the Chakari Basin, Afghanistan

was the water sample from well W5, which had a δ15N ratio 

of +10.24 per mil. The higher δ15N value at this site suggests 

some of the nitrogen is from human or animal waste. Well W5 

is in an area of undifferentiated sands with the highest population density found in the basin (150–336 people per square 

kilometer), making it vulnerable to anthropogenic influences. 

A high nitrate concentration (12.9 mg/L as N), detections of 

coliform bacteria, and a δ15N value greater than +10 per mil 

all indicate possible anthropogenic contamination in groundwater at this site. Groundwater from well W5 also was likely 

recharged in the past 11 years, based on apparent ages from 

anthropogenic tracers (see “Chlorofluorocarbons and Sulfur 

Hexafluoride” section). Well W5 is a large-diameter hand-dug 

well lined with stones that allow for natural seepage into the 

well and is likely more vulnerable to surface contamination 

than modern wells that are constructed with more rigorous, 

sanitary methods.

Hydrogen and Oxygen Isotopes of Water

The isotopic ratios of hydrogen (δ2H) and oxygen (δ18O) 

in water are used to differentiate between higher and lower 

elevation sources of the water in streams and aquifers (Clark 

and Fritz, 1997). Low isotopic ratios of hydrogen and oxygen 

in water reflect water from high-elevation source areas where 

a large part of the water draining to streams and recharging 

groundwater originates as snowmelt. In the Chakari Basin, 

well W8 had the lowest δ2

H (–66 per mil) and δ18O (–10 per 

mil) ratios, suggesting that a greater part of the groundwater 

at this well originated as high-elevation source water from 

snowmelt. Well W8 is not immediately adjacent to mountains; 

therefore, snowmelt-derived recharge to this well must have 

followed a relatively long flow path. All samples from the 

Chakari Basin plotted to the left of the global meteoric water 

line (fig. 13; Rozanski and others, 1993), indicating that no 

substantial evaporation has occurred. Chloride concentrations 

in most groundwater samples in the Chakari Basin were 

about 10 times higher than the chloride concentration 

in the surface water sample (see “Mass-Concentration 

Ratios” section). Because δ2

H and δ18O ratios indicated no 

substantial evaporation, the elevated chloride concentrations 

in groundwater most likely were the result of water uptake 

by vegetation because transpiration removes water without 

altering δ18O and δ2

H compositions (Mack and others, 2010) 

but does concentrate dissolved solutes, such as chloride, in the 

water that is left behind.

Groundwater in the Chakari Basin had δ18O and δ2

H 

isotopic ratios most similar to groundwater from the Paghman 

and upper Kabul subbasins (fig. 14). Deuterium excess, 

defined as δ2

H minus eight times δ18O (Dansgaard, 1964), 

ranged from 11.4 to 16.2 for groundwater in the Chakari Basin 

(appendix 3), compared with 12 to 19 in the Paghman and 

upper Kabul subbasins. The deuterium excess is a function 

of the relative humidity; a value of +20 indicates 70 percent 

relative humidity, and a value of +10 indicates 85 percent 

relative humidity (global mean relative humidity). δ18O and 

δ2

H isotopic compositions indicate that the Chakari, Paghman, 

and upper Kabul subbasins have source-water origins from 

similar altitudes (approximately 2,000 to 4,000 m) and 

semiarid climates (Mack and others, 2010). The surface-water 

sample from the Chakari River had δ18O and δ2

H isotopic 

ratios and a deuterium excess value (+16) similar to the values 

from the upper Kabul River (fig. 14; Mack and others, 2010). 

The Chakari and upper Kabul River δ18O and δ2

H isotopic 

ratios similarly indicate no substantial evaporation, which is 

unusual for a semiarid climate.

Chlorofluorocarbons and Sulfur Hexafluoride

CFCs are stable, synthetic, halogenated alkanes that 

were developed in the early 1930s and have been used in a 

wide range of industrial and refrigerant applications. CFCs 

are a useful tool for determining the apparent residence times 

(“ages”) of water on time scales of 50 to 70 years in age 

(International Atomic Energy Agency, 2006). SF6 is a trace 

atmospheric gas that is primarily of anthropogenic origin but 

also occurs naturally in fluid inclusions of some minerals 

and igneous rocks. SF6 is a useful tool in dating groundwater 

that originated as recharge since 1970 (Busenberg and 

Plummer, 2000).

All 13 groundwater samples contained CFC–11, CFC–12, 

CFC–113, and SF6

 (appendix 3), indicating that young water 

or water mixtures containing a part of young water were present in all wells, springs, and the kareze. Apparent ages for the 

young part of water calculated from CFC concentrations using 

a piston-flow model ranged from 10 to 50 years (appendix 3). 

SF6-derived ages calculated using piston-flow modeling of 

SF6

 concentrations were slightly younger (4 to 31 years) but 

comparable to the CFC-derived ages.

Tritium, Helium, and Carbon-14 Isotopes

Tritium, helium, and 14C also can provide information 

on the age distribution of groundwater. Tritium is a heavy 

isotope of hydrogen that radioactively decays to helium with 

a half-life of 12.3 years (Drever, 1988). Tritium is part of the 

water molecule and is not affected by water-rock reactions; 

its activities change only through changes in activities in 

precipitation and through radioactive decay. Tritium activities 

can be used to differentiate between water that has been 

recharged since 1953 and water recharged prior to the 1950s. 

Aboveground testing of hydrogen bombs from 1952 to 1969 

added a large amount of tritium to the atmosphere, with a 

peak of nearly 3,500 tritium units (TU) in 1963 in Afghanistan 

(International Atomic Energy Agency, undated). Low levels 

of tritium (5 to 10 TU) are produced continuously by cosmic 

ray bombardment of the atmosphere (Clark and Fritz, 1997). 

Even with the variability in tritium content of precipitation 

over time, groundwater that has been recharged since 1953 

(postbomb) likely contains more than 0.5 TU, whereas 

groundwater that was recharged before 1953 (prebomb) likely 

contains less than 0.5 TU.
Water Quality, Chemistry, and Isotopes 27

Chakari GW

Istalef River

Barik Ab River

Panjsher River

Shomali GW

Logar River

Logar GW

Kabul River

Kabul GW

Deh Sabz GW

Eastern GW

Upper Kabul River 

Pagham River

Pagham GW

Western GW

 Delta oxygen-18, in parts per thousand relative to VSMOW

Delta hydrogen-2, in parts per thousand relative to VSMOW 

Kabul Basin sites

 ordered by north to south 

 by groundwater subbasins

Global meteoric water line

EXPLANATION

Chakari River

Panjsher subbasin

Shomali

Deh Sabz

Central Kabul

Pagham and Upper Kabul

Logar

Chakari Basin

Western and Eastern fronts

-70

-65

-60

-55

-50

-45

-40

-11 -10 -9 -8 -7 -6

Figure 14. The hydrogen-2 (2H) versus oxygen-18 (18O) isotopic composition, relative to Vienna Standard Mean Ocean Water 

(VSMOW; Rozanski and others, 1993), of rivers and groundwater (GW; including springs and karezes) in the Chakari and Kabul 

Basins, Afghanistan. All data except for those for the Chakari Basin are from Mack and others (2010).

The tritium activity for well W8 (0.05 TU; appendix 3) 

indicates that most of the groundwater from this well was 

recharged before 1953. Samples from six of the remaining 

wells, four springs, and the kareze had tritium concentrations in the range of 2.0 to 9.7 TU, indicating that much of 

the groundwater from these sites was recharged after 1953 

(appendix 3). Tritium activities agree with other inorganic and 

anthropogenic tracersfor all wells and springs and the kareze 

with the exception of well W5. Well W5 is a hand-dug well 

with signs of surface contamination, including high nitrate 

concentration (12.9 mg/L as N) and detections of coliform 

bacteria. The tritium activity reported for well W5 (–0.01 TU; 

appendix 3) is very likely an erroneous value because it 

indicates groundwater recharged before 1953. This conclusion 

conflicts with all other indicators for well W5. Apparent ages 

for the water at well W5 based on piston-flow modeling of 

CFC and SF6 data are between 7 to 24 years.

Helium has two stable isotopes, helium-3 and helium-4. 

Helium-3 is added to groundwater by the decay of tritium, 

and the 3

H:3He ratio can be used to determine the apparent age 

of groundwater. However, helium in groundwater originates 

from several sources, and these sources must be accounted 

for in order to determine the apparent age of groundwater 

from the 3

H:3He ratio. Helium can become dissolved in 

groundwater from the atmosphere, from excess air (Busenberg 

and Plummer, 2000; Stute and Schlosser, 2000) in the 

unsaturated zone of an aquifer in contact with the water table, 

and from terrigenic helium derived from uranium and thorium 

radioactive decay reactions in the Earth’s crust (Mamyrin and 

Tolstikhin, 1984).

Determination of the 3

H:3He-derived groundwater age 

is done by measuring the time needed for the original tritium 

concentration to decay to the measured tritium concentration, 

once all other helium sources have been accounted for. The
28 Hydrogeology and Water Quality of the Chakari Basin, Afghanistan

3

H:3He age cannot be determined if any of the following four 

conditions occur: (1) tritium concentration is too low (less 

than 1 TU), (2) excessive amounts of terrigenic helium are 

dissolved in the water sample, (3) degassing of the sample 

occurred, or (4) negative values are calculated for the helium-3 

derived from decay of tritium that was in the sample at the 

time of recharge (L.N. Plummer, U.S. Geological Survey, written commun.). Degassing of a sample is indicated when excess 

helium-4 is less than excess neon; excess refers to the difference between the concentration of a gas in the groundwater 

sample and the expected concentration in the groundwater at 

equilibrium with atmospheric concentrations under the conditions at recharge (L.N. Plummer, U.S. Geological Survey, 

written commun.). 3

H:3He results were valid for only 5 of the 13 groundwater samples owing to low tritium content in wells W5 and 

W8; large excesses of terrigenic helium in wells W1 and W4; 

degassing in kareze K1, spring S1, and wells W1, W2, W5, 

and W6; and negative calculated values of helium-3 in spring 

S1 and wells W2, W5, W6, and W8 (L.N. Plummer, U.S. Geological Survey, written commun.). The apparent 3

H:3He age for 

springs S2, S3, and S4 and wells W3 and W4 ranged from 1.3 

to 20.3 years (appendix 3).

The best way of evaluating the accuracy of results from 

the 3

H:3He method is to compare them with the results of other 

age-dating techniques. 3

H:3He ages were similar or slightly 

younger than ages derived from CFC and SF6

 data. The sum 

of tritium plus helium-3 provides the tritium concentration at 

the time of recharge if the sample has not been diluted with 

old water (L.N. Plummer, U.S. Geological Survey, written 

commun.); comparison of the apparent age derived from the 

3

H:3He method with the initial tritium activity thus calculated 

is another way to evaluate the accuracy of the 3

H:3He ages. 

The three springs are all young water (0–9 years), based on 3

H:3He ages and initial tritium activities. The 3H:3He age of 

the water sample from well W4 is 17 years; the initial tritium 

activity of 25 TU in the sample suggests little or no dilution 

with old water. The initial tritium activity of 6.8 TU for the 

water sample from well W3 is relatively low for the 3H:3He 

age of 20 years. Assuming that the part of old water is free 

of tritium, well W3 appeared to contain about 27 percent of 

20-year-old water diluted with old, tritium-free water (L.N. 

Plummer, U.S. Geological Survey, written commun.).

The radioactive isotope of carbon 14C is incorporated 

into dissolved carbonate species in water. Activities of 14C 

in dissolved carbon in groundwater are determined by the 

activities in equilibrium with atmospheric 14C at when the 

groundwater was recharged. Because 14C decays with a 

half-life of 5,730 years, low activities of 14C, relative to 

modern values in groundwater, generally indicate the presence 

of groundwater that is several thousands of years old. Thus, 

14C is a useful tool for age-dating older groundwater sources 

ranging in age from approximately 2,000 to 40,000 years from 

the date of recharge. However, some reactions between rock 

and water, such as the dissolution of limestone, can dilute the 

14C in dissolved inorganic carbon by adding dissolved carbon 

to the groundwater from old rock sources that contain little or 

no 14C. Left uncorrected, this would result in modern 14C water 

samples appearing to be old.

Using the revised Fontes and Garnier model (Han and 

Plummer, 2013) and assuming the samples were all old water 

(greater than 60 years old), the uncorrected 14C modeled ages 

for wells W7 and W8 were 2,200 and 4,100 years, respectively 

(appendix 3; L.N. Plummer, U.S. Geological Survey, written 

commun.). These are minimum age estimates before accounting for the possibility that the old water was mixed with 

younger water containing “artificial” 14C. These uncorrected 14C modeled ages suggest that a large part of water from these 

wells is old groundwater.

Comparisons of apparent ages based on 14C data with 

CFC–11, CFC–12, CFC–113, and SF6

 concentrations data 

indicate that wells W3, W7, and W8 were most likely mixtures 

of young and old water, whereas the rest of the wells and 

springs and the kareze contain primarily young water (fig. 15; 

L.N. Plummer, U.S. Geological Survey, written commun.). 

The parts of young and old water in wells W3, W7, and W8 

were calculated assuming binary dilution. Binary dilution 

equations were solved using assumptions that old water 

(greater than 60 years old) would be free of the four tracers 

and young water would have concentrations similar to the 

concentrations in northern hemisphere air in January 2013. We 

thus determined that wells W3 and W7 contain approximately 

60 percent old water, and well W8 contains 80 percent old 

water (appendix 3; L.N. Plummer, U.S. Geological Survey, 

written commun.).

Following the linear relation between 14C activity and 

concentrations of the CFC tracers, the old part of water (identified by the y intercept (fig. 15), where the concentration of the 

CFC tracer is equal to zero) contains approximately 20 percent 

modern 14C (L.N. Plummer, U.S. Geological Survey, written 

commun.). Radiocarbon modeling of this corrected 20 percent 

modern 14C using a revised Fontes and Garnier model (Han 

and Plummer, 2013) indicates that the actual age of the old 

part of water in wells W3, W7, and W8 is 7,200 to 7,900 years 

(L.N. Plummer, U.S. Geological Survey, written commun.).
Water Quality, Chemistry, and Isotopes 29

0

20

40

60

80

100

0 50 100 150 200 250

CFC−11 concentration, in parts per trillion by volume

 Carbon−14 activity, in percent modern Carbon−14 activity, in percent modern

 Carbon−14 activity, in percent modern Carbon−14 activity, in percent modern

CFC−12 concentration, in parts per trillion by volume

0

20

40

60

80

100

0 100 200 300 400 500 600

CFC−113 concentration, in parts per trillion by volume

0

20

40

60

80

100

0 10 20 30 40 50 60 70 80

SF6 concentration, in parts per trillion by volume

0

20

40

60

80

100

0 1 2 3 4 5 6 7

A. CFC−11 B. CFC−12

C. CFC−113 D. SF6

Figure 15. Carbon-14 activities in relation to concentrations of chlorofluorocarbons (CFCs) A, trichlorofluoromethane (CFC–11), 

B, dichlorodifluoromethane (CFC–12), C, trichlorotrifluoroethane (CFC–113), and D, sulfur hexafluoride (SF6

) in groundwater samples 

from the Chakari Basin, Afghanistan, 2012–2013.
30 Hydrogeology and Water Quality of the Chakari Basin, Afghanistan

Summary and Conclusions

The U.S. Geological Survey and the Afghanistan 

Geological Survey assessed the hydrogeology and water 

quality of the Chakari Basin, a 391-square-kilometer (km2

) 

watershed near Kabul, Afghanistan. This assessment forms 

the basis of an understanding of the water resources in an area 

of Afghanistan with considerable copper and other mineral 

resources. Water quality, chemical, and isotopic samples were 

collected at eight wells, four springs, one kareze, and the 

Chakari River in a basin-fill aquifer in the Chakari Basin by 

the Afghanistan Geological Survey.

The water quality in the sparsely populated Chakari Basin 

is influenced by the geology and climate of the area. Concentrations of many trace elements in groundwater of the Chakari 

Basin are elevated, reflecting the mineralized geology and 

dry climate of the area. However, none of the trace element 

concentrations exceeded a World Health Organization humanhealth benchmark or a U.S. Environmental Protection Agency 

drinking-water standard or guideline.

A combination of interactions between water and rock 

and evapotranspiration were the major factors affecting 

groundwater chemistry in the Chakari Basin. The major 

ion chemistry of groundwater was calcium-magnesiumbicarbonate-type water. Solute concentrations in groundwater 

were about one order of magnitude higher than concentrations 

in the surface water from the Chakari River. Stable hydrogen 

and oxygen isotope results from groundwater samples 

indicated no substantial evaporation (all samples plotted 

above the global meteoric water line). High concentrations 

of zinc and copper in groundwater samples from the Chakari 

Basin likely reflect the metasedimentary rocks, particularly 

dolomitic marble, of the North Aynak-Taghar mineral area. 

Higher ratios of calcium, magnesium, and sulfate relative to 

chloride in surface water compared with those in groundwater 

indicated interactions between water and rock, including 

calcite and gypsum precipitation and cation exchange in 

shallow groundwater.

The nitrate values of 2 to 5 milligrams per liter as nitrogen (mg/L as N) for most of the groundwater samples from the 

Chakari Basin may be the result of agricultural contamination, 

but the isotope composition of nitrate values suggest that natural soil nitrate may be the predominant source. Detection of 

coliform bacteria, high concentrations of nitrate (12.9 mg/L as 

N), and a nitrate isotope value greater than 10 per mil indicate 

the vulnerability of hand-dug wells (such as well W5; fig. 4) to 

surface contamination sources. Concentrations of chlorofluorocarbon concentrations and sulfur hexafluoride and carbon-14 

activities indicated that groundwater from wells W3, W7, 

and W8 consists of a mixture of old and young groundwater, 

with the old part being 7,200 to 7,900 years. All other wells 

and springs and the kareze likely have groundwater that was 

recharged less than 50 years ago.

Isotopic analysis of the water samples indicates that 

some of the groundwater travels thousands of years to reach a 

point of discharge (that is, a well, spring, or kareze), whereas 

another component of the groundwater travels only a few 

years to decades to reach a point of discharge. It is likely that 

the older water represents flow through the fractured bedrock 

of the surrounding valley walls and underlying bedrock to the 

basin-fill sediments. For example, although the surficial sediments at well W7 are about 40 meters (m) thick, the surficial 

basin-fill sediments extend only about a 1 kilometer upgradient from the well. The source of groundwater at well W7 is 

likely groundwater that has flowed or drained slowly through 

fractured bedrock. It is likely that groundwater in the shallow upper sediments (fig. 7) originates from the small amount 

of recharge from modern (less than 40 years) precipitation 

that infiltrates at drainage channels, and groundwater deep in 

the basin-fill sediments is thousands of years old. Analysis 

of water-level fluctuations and chemical analysis of water 

indicates that considerable recharge may occur in the basinfill aquifer through infiltration of surface water, originating 

primarily as snowmelt from upland areas of the Chakari Basin, 

at the Chakari River and other stream channels in the basin. 

Recharge was estimated to be 2 × 10-4 meters per day (m/d) 

at one point adjacent to the Chakari River. Recharge at this 

point reflects primarily inflow from upland areas and secondarily direct precipitation. Seepage losses and infiltration from 

perennial and, to a lesser degree, ephemeral streams traversing 

areas underlain by unconsolidated sediments likely represent 

sources of concentrated recharge to the underlying aquifers. 

Areal basinwide recharge estimated from historical streamflows leaving the basin indicates an average annual recharge 

rate of only about 7 × 10-5 m/d. The source of this recharge 

is most likely derived from snow on upland mountains and 

subsequent meltwater-fed streams.

The average saturated thickness indicated by wells 

drilled in the basin is approximately 20 m. In the center of 

the Chakari Basin, saturated basin-fill sediments are as much 

as 100 m thick, but the saturated thickness in most areas near 

the center of the basin is likely to be 30 to 60 m. Groundwater in the basin-fill aquifers consists of a near-surface young 

component, years to decades in age, and a deep component 

hundreds to thousands of years old that likely has traveled 

from upland bedrock areas. These groundwater resources meet 

the drinking-water needs of the existing villages, which rely 

on low-capacity hand pumps for drinking-water supply and 

rely on surface water for irrigation. There may be sufficient 

groundwater storage in the center of the basin for additional 

groundwater withdrawals. However, the installation and use of 

wells with high-capacity pumps would need careful evaluation, particularly with respect to the existing water supplies of 

the surrounding communities. Sustainable use of water in the 

Chakari Basin for industrial purposes would likely require an 

integrated surface water and groundwater assessment, using 

a groundwater flow model, and regional management strategies that consider groundwater and surface-water storage and 

strategies for enhancing the infiltration of surface water during 

periods of high streamflow for groundwater recharge.
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Appendixes 1–3

These appendixes are available at http://pubs.usgs.gov/sir/2014/5113/.

Appendix 1. Physical Properties, Nutrient, Bacteria, 

and Major Ion Water-Quality Data for the Chakari Basin, 

Afghanistan

Appendix 2. Trace-Element Water-Quality Data for the 

Chakari Basin, Afghanistan

Appendix 3. Inorganic and Anthropogenic Tracer and 

Dissolved Gas Data for the Chakari Basin, Afghanistan
Prepared by the Pembroke and West Trenton 

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Mack and others—Hydrogeology and Water Quality of the Chakari Basin, Afghanistan—Scientific Investigations Report 2014–5113

ISSN 2328-031X (print)

ISSN 2328-0328 (online)

http://dx.doi.org/10.3133/sir20145113