U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet 2012–3032

January 2013 Printed on recycled paper

U.S. Geological Survey and the California State Water Resources Control Board

Groundwater Quality in the Owens Valley, 

California

Groundwater provides more than 40 percent of California’s drinking water. To protect this vital 

resource, the State of California created the Groundwater Ambient Monitoring and Assessment (GAMA) 

Program. The Priority Basin Project of the GAMA Program provides a comprehensive assessment of the 

State’s groundwater quality and increases public access to groundwater-quality information. Owens 

Valley is one of the study areas being evaluated. 

The Owens Study Area Overview of Water Quality

GAMA’s Priority Basin Project evaluates the quality of untreated groundwater. 

However, for context, benchmarks established for drinking-water quality are used 

for comparison. Benchmarks and definitions of high, moderate, and low concentrations are discussed in the inset box on 

page 3. The USGS sampled 40 wells for 

this assessment; data from the California 

Department of Public Health database were 

used to supplement USGS data.

Many inorganic constituents occur 

naturally in groundwater. The concentrations of the inorganic constituents can be 

affected by natural processes as well as by 

human activities. In the Owens study area, 

one or more inorganic constituents were 

present at high concentrations in 22% of 

the primary aquifers and at moderate concentrations in 20%.

Organic constituents are present in 

products used in the home, business, industry, and agriculture. Organic constituents 

can enter the groundwater system through 

normal usage, spills, or improper disposal. 

In the Owens study area, no organic constituents were present at high or moderate 

concentrations.

The Owens study area is 

approximately 1,030 square miles 

(2,668 square kilometers) and includes 

the Owens Valley groundwater basin 

(California Department of Water 

Resources, 2003). Owens Valley has a 

semiarid to arid climate, with average 

annual rainfall of about 6 inches 

(15 centimeters). The study area has 

internal drainage, with runoff primarily 

from the Sierra Nevada draining east 

to the Owens River, which flows 

south to Owens Lake dry lakebed 

at the southern end of the valley. 

Beginning in the early 1900s, the City 

of Los Angeles began diverting the 

flow of the Owens River to the Los 

Angeles Aqueduct, resulting in the 

evaporation of Owens Lake and the 

formation of the current Owens Lake 

dry lakebed. Land use in the study 

area is approximately 94 percent (%) 

natural, 5% agricultural, and 1% urban. 

The primary natural land cover is 

shrubland. The largest urban area is 

the city of Bishop (2010 population of 

4,000).

Groundwater in this basin is used 

for public and domestic water supply 

and for irrigation. The main waterbearing units are gravel, sand, silt, and 

clay derived from surrounding mountains. Recharge to the groundwater system is primarily runoff from the Sierra Nevada, and by direct infiltration of irrigation. 

The primary sources of discharge are pumping wells, evapotranspiration, and underflow to the Owens Lake dry lakebed. The primary aquifers in Owens Valley are defined 

as those parts of the aquifers corresponding to the perforated intervals of wells listed 

in the California Department of Public Health database. Public-supply wells in Owens 

Valley are completed to depths between 210 and 480 feet (64 to 146 meters), consist of 

solid casing from the land surface to a depth of 50 to 80 feet (15 to 24 meters), and are 

screened or perforated below the solid casing.

NEVADA

Los Angeles Aqueduct

118°30’

37°30’

36°30’

37°

36°

38°

118°

0 5 10 20 MILES

0 5 10 20 KILOMETERS

Bishop

Owens Dry

Lakebed

Owens River Owens River

SIERRA NEVADA

Owens Valley

Study Area

EXPLANATION

Lake

Dry Lakebed

Urban area

Alluvium

Hard rock

Study area 

boundary

Indian ells

High Moderate

CONSTITUENT CONCENTRATIONS

Low or not detected 

Pie charts illustrate the percentage of the primary 

aquifers, on a areal basis, with concentrations in the 

three specified categories.

22

20 58

Organic

constituents

Inorganic

constituents

Number analyzed: 27 Number analyzed: 79

100
RESULTS: Groundwater Quality in the Owens Study Area

Inorganic Constituents with Human-Health Benchmarks

Trace elements are naturally present in the minerals in rocks and soils, and in the 

water that comes into contact with those materials. In the Owens study area, trace elements with human-health benchmarks were present at high concentrations in 15% of the 

primary aquifers, on an areal basis, and at moderate concentrations in 13%. Of the 17 

trace elements with human-health benchmarks analyzed in this study, 4 were detected at 

high concentrations: arsenic, boron, fluoride, and molybdenum. 

Radioactivity is the release of energy or energetic particles during structural 

changes in the nucleus of an atom. Most of the radioactivity in groundwater comes 

from decay of naturally occurring isotopes of uranium and thorium that are present in 

minerals in the aquifer. In the Owens study area, radioactive constituents were found 

at concentrations above benchmarks in 10% of the primary aquifers, and at moderate 

concentrations in 15%. Six radioactive constituents were analyzed; of these, gross alpha 

radioactivity and uranium were detected above human-health benchmarks. Radon was 

detected at values within one-half of the proposed upper benchmark.

Nutrients, such as nitrate and nitrite, are naturally present at low concentrations in 

groundwater. High and moderate concentrations generally occur as a result of human 

activities, such as fertilizer application, livestock waste, or septic-system seepage. Of 

the three nutrients with health-based benchmarks analyzed, none were detected at concentrations above benchmarks.

Inorganic Constituents with Non-Health Benchmarks

(Not included in water-quality overview charts shown on the front page)

Other inorganic constituents, such as total dissolved solids and manganese, affect 

the aesthetic properties of water, such as taste, color, or odor. In the Owens study area, 

these constituents were present at high concentrations in 15% of the primary aquifers, 

and at moderate concentrations in 8%. Of the seven constituents with non-health-based 

benchmarks that were analyzed, three (iron, manganese, and total dissolved solids) were 

detected at concentrations above benchmarks.

Special Interest: Perchlorate

Perchlorate is an inorganic constituent which has been regulated in California 

drinking water since 2007. It is an ingredient in rocket fuel, fireworks, safety flares, 

may be present in some fertilizers, and also occurs naturally at low concentrations in 

groundwater. In the Owens study area, perchlorate was not detected at high or moderate 

concentrations in the primary aquifers.

Other

inorganic

constituents

Perchlorate

13

15

71

75

78

15

8

100

100

10

15

Trace 

elements

Radioactive

constituents

Nutrients

INORGANIC CONSTITUENTS
RESULTS: Groundwater Quality in the Owens Study Area

Organic Constituents with Human-Health Benchmarks

The Priority Basin Project uses laboratory methods that can detect the presence 

of volatile organic compounds (VOCs) and pesticides at low concentrations, far below 

human-health benchmarks. VOCs and pesticides detected at these low concentrations 

can be used to help trace water from the land surface into the aquifer system.

Volatile Organic Compounds

VOCs are present in many household, commercial, industrial, and agricultural 

products and are characterized by their tendency to volatilize into the air. Of 56 VOCs 

with health-based benchmarks analyzed in the Owens study area, none were present at 

high or moderate concentrations in the Owens primary aquifers.

Pesticides

Pesticides are used on lawns, in gardens, around buildings, along roads, and in 

agriculture to help control unwanted vegetation (weeds), insects, fungi, and other pests. 

In the Owens study area, pesticides were not detected or were only detected at low 

concentrations. Of the 20 pesticides with health-based benchmarks that were analyzed, 

none were detected at high or moderate concentrations in the Owens primary aquifers.

BENCHMARKS FOR EVALUATING GROUNDWATER QUALITY

GAMA’s Priority Basin Project uses benchmarks established for drinking 

water to provide context for evaluating the quality of untreated groundwater. After 

withdrawal, groundwater may be disinfected, filtered, mixed, or exposed to the 

atmosphere before being delivered to consumers. Federal and California regulatory 

benchmarks for protecting human health (Maximum Contaminant Level, MCL) are 

used when available. Otherwise, nonregulatory benchmarks for protecting human 

health (Notification Level, NL, and Lifetime Health Advisory, HAL) and nonregulatory 

benchmarks for protecting aesthetic properties such as taste and odor (Secondary 

Maximum Contaminant Level, SMCL) are used. 

High

Moderate

EX

Low or not detected

AMPLE Values are a percentage of the area of the primary aquifers 

with concentrations in the three specified categories.

CONSTITUENT CONCENTRATIONS

High, moderate, and low concentrations are defined relative to benchmarks

Concentrations are considered high if they are greater than a benchmark. For inorganic constituents, concentrations are moderate

if they are greater than one-half of a benchmark. For organic and special-interest constituents, concentrations are considered moderate

if they are greater than one-tenth of a benchmark; this lower threshold was used because organic constituents are generally less 

prevalent and have smaller concentrations relative to benchmarks than inorganic constituents. Low concentrations include nondetections and values less than moderate concentrations. Methods for evaluating water quality are discussed by Milby Dawson and 

Belitz (2012).

ORGANIC CONSTITUENTS

Pesticides

Volatile

organic

compounds

100

100
Trace Element Concentrations Throughout the 

California Desert Region

Trace elements were present at high concentrations in all of the Desert Region 

primary aquifers. In the Owens study area, trace elements were high in 15% of the 

primary aquifers, which is the smallest percentage of high trace elements in the Desert 

region (Milby Dawson and Belitz, 2012). The trace elements with the highest areal 

percentages in Owens Valley were boron (high concentrations in 10% of the primary 

aquifers), arsenic (8%), and molybdenum (5%). Boron and arsenic were detected at high 

concentrations in all of the Desert primary aquifers; molybdenum was detected at high 

concentrations in five of the six Desert Region study areas.

Priority Basin Assessments 

GAMA’s Priority Basin Project 

(PBP) assesses water quality in that part 

of the aquifer system used for drinking 

water, primarily public supply. Water 

quality in shallower and deeper parts 

may differ from water quality in the 

primary aquifers. GAMA’s Domestic 

Well Project assesses water quality 

in the shallower parts of the aquifer 

system. Ongoing assessments are being 

conducted in more than 120 basins 

throughout California. 

The PBP assessments are based 

on a comparison of constituent 

concentrations in untreated groundwater 

with benchmarks established for the 

protection of human health and for 

aesthetic concerns. The PBP does not 

evaluate the quality of drinking water 

delivered to consumers. 

The PBP uses two approaches for 

assessing groundwater quality. The first 

approach uses a network of wells to 

provide a statistically based assessment 

of the status of groundwater quality. The 

second approach uses additional wells 

to help assess the factors that affect 

water quality. Both approaches use 

data routinely collected for regulatory 

compliance, as well as data collected 

by the PBP. The PBP includes chemical 

analyses not generally available 

as part of regulatory compliance 

monitoring, including measurements at 

concentrations much lower than humanhealth benchmarks, and measurement of 

constituents that can be used to trace the 

sources and movement of groundwater.

By Barbara J. Milby Dawson and Kenneth Belitz

SELECTED REFERENCES

California Department of Water Resources, 2003, California’s groundwater: California 

Department of Water Resources Bulletin 118, 246 p., available at

http://www.water.ca.gov/groundwater/bulletin118/update2003.cfm

Densmore, J.N., Fram, M.S., and Belitz, K., 2009, Ground-water quality data in the 

Owens and Indian Wells Valleys study unit, 2006—Results from the California 

GAMA Program: U.S. Geological Survey Data Series 427, 86 p., available at

http://pubs.usgs.gov/ds/427

Milby Dawson, B.J., and Belitz, K., 2010, Status of groundwater quality in the 

 California Desert Region, 2006–2008—California GAMA Program Priority Basin 

 Project: U.S. Geological Survey Scientific Investigations Report 2010-5040, 100 p.

For more information

Technical reports and hydrologic 

data collected for the GAMA Program 

may be obtained from:

GAMA Program Unit

U.S. Geological Survey

California Water Science Center

4165 Spruance Road, Suite 200

San Diego, CA 92101

Telephone number: (619) 225-6100

WEB: http://ca.water.usgs.gov/gama

GAMA Program Unit

State Water Resources Control Board

Division of Water Quality

PO Box 2231, Sacramento, CA 95812

Telephone number: (916) 341-5779

WEB: http://www.waterboards.ca.gov/gama/

0 25 50

0 25 50 100 KILOMETERS

100 MILES

Owens

Valley

Indian Wells

Mojave

Coachella

NEVADA

ARIZONA

MEXICO

CALIFORNIA

Colorado River

Desert Region Study Areas

0%

20%

40%

60%

80%

100%

0%

20%

40%

60%

80%

100%

0%

20%

40%

60%

80%

100%

0%

20%

40%

60%

80%

100%

Owens

Indian Wells

Coachella

Colorado River

Antelope

Mojave

High aquifer proportion

EXPLANATION

Moderate aquifer proportion

Trace Elements

Molybdenum

Arsenic

Boron

Percentage of area of primary aquifers with concentrations in the specified categories

0%

20%

40%

60%

80%

100%

0%

20%

40%

60%

80%

100%

0%

20%

40%

60%

80%

100%

0%

20%

40%

60%

80%

100%

Owens

Indian Wells

Coachella

Colorado River

Antelope

Mojave

High aquifer proportion

EXPLANATION

Moderate aquifer proportion

Trace Elements

Molybdenum

Arsenic

Boron

Percentage of area of primary aquifers with concentrations in the specified categories