Water Quality in the

Upper Snake River Basin

Idaho and Wyoming, 1992–95

U.S. Department of the Interior

U.S. Geological Survey Circular 1160

science for a changing world
A COORDINATED EFFORT

Chief, NAWQA Program

U.S. Geological Survey

Water Resources Division

12201 Sunrise Valley Drive, M.S. 4

Reston, VA 20192

FOR ADDITIONAL INFORMATION ON THE

NATIONAL WATER-QUALITY ASSESSMENT (NAWQA) PROGRAM:

Numerous agencies and individuals provided information and assistance with data collection and data processing as 

this study. The authors acknowledge the following agencies for their cooperation: Idaho Agricultural Statistics Servic

State Department of Agriculture; Idaho Division of Environmental Quality (formerly Idaho Department of Health and 

Division of Environmental Quality); Idaho Department of Water Resources; Idaho Department of Fish and Game; Un

of Idaho, Cooperative Extension Service; University of Idaho, Agricultural Research Service; U.S. Natural Resource 

vation Service; U.S. Environmental Protection Agency; U.S. Fish and Wildlife Service; and Wyoming Game and Fish 

ment. Individuals from the U.S. Geological Survey who provided field assistance include Jay Bateman, Michael Beckw

Craig Bowers, Stephanie Eisenbarth, Jeff Foster, Steve Goodbred, Kirk Miller, Bill Mullins, Terry Short, Marc Sylvest

Waite, and Cathy Wolf. Special thanks go to Ken Skinner of the U.S. Geological Survey for providing valuable assista

ing all phases of the study; and Alan Haggland, Sarah Ryker, and Jon Scott of the U.S. Geological Survey for productio

Compound Detections and Concentrations table.

Upper Snake River Basin Study Unit, contact:

Derrill Cowing, District Chief

U.S. Geological Survey

Water Resources Division

230 Collins Road

Boise, ID 83702-4520

Information on the NAWQA Program also is available on the Internet via the World Wide Web. Yo

connect to the NAWQA Home Page using the Universal Resources Locator (URL):

http://wwwrvares.er.usgs.gov/nawqa/nawqa_home.html

The Upper Snake River Basin Study Unit’s Home Page is at URL:

http://wwwidaho.wr.usgs.gov/nawqa/usnk_home.html

Photograph on front cover: Taggart Creek on the east side of the Teton Range, Grand Teton National Park, Wyoming

(photograph by M.G. Rupert, U.S. Geological Survey).

Photograph on page 1: Sampling for benthic invertebrates in the Big Lost River, Idaho (photograph by T.R. Maret,

U.S. Geological Survey).

Photographs on back cover: 1. Sprinkler irrigation of crops near Pocatello, Idaho (photograph © 1980 by W.H. Mullins and

 published with permission).

2. Fall harvest of barley in the Teton River Valley, Idaho (photograph © 1995 by W.H. Mullins

 and published with permission).
U.S. GEOLOGICAL SURVEY CIRCULAR

Water Quality in the Upper Snake River Basi

Idaho and Wyoming, 1992–95

1160

By G.M. Clark, T.R. Maret, M.G. Rupert, M.A. Maupin,

W.H. Low, and D.S. Ott

CONTENTS

National Water-Quality Assessment

Program .......................................................

Summary of major issues and findings .......

Environmental setting and hydrologic

conditions .....................................................

Major issues and findings..............................

Water-quality conditions in a

national context ...........................................

Study design and data collection .................

Summary of compound detections and

concentrations .............................................

References ........................................................

Glossary............................................................
Library of Congress Cataloging-in-Publications Data

The use of firm, trade, and brand names in this report is for identification purposes only and

does not constitute endorsement by the U.S. Government

U.S. DEPARTMENT OF THE INTERIOR

BRUCE BABBITT, Secretary

U.S. GEOLOGICAL SURVEY

Thomas J. Casadevall, Acting Director

Free on application to the

U.S. Geological Survey

Information Services

Box 25286, Federal Center

Denver, CO 80225

Water quality in the Upper Snake River Basin, Idaho and Wyoming,

1992–95 / by G.M. Clark ... [et al.].

p. cm. -- (U.S. Geological Survey circular : 1160)

Includes bibliographical references (p. ).

ISBN 0-607-89104-1 (alk. paper)

1. Water quality--Snake River Watershed (Wyo.-Wash.) I. Clark,

G. M. (Gregory M.), 1958– . II. Series.

TD225.S47W38 1998

363.739'42'097961--dc21 98-15371

CIP

1998
NATIONAL WATER-QUALITY ASSESSMENT PROG

Began in 1991

Began in 1994

Began in 1997

Not scheduled yet

EXPLANATION

decade to evaluate changes in water-quality conditions.

NAWQA assessments rely heavily on existing information

collected by the USGS and many other agencies as well as

the use of nationally consistent study designs and methods of

sampling and analysis. Such consistency simultaneously provides information about the status and trends in water-quality

conditions in a particular stream or aquifer and, more importantly, provides the basis to make comparisons among watersheds and improve our understanding of the factors that

affect water-quality conditions regionally and nationally.

This report is intended to summarize major findings that

emerged between 1992 and 1995 from the water-quality

assessment of the Upper Snake River Basin Study Unit and

to relate these findings to water-quality issues of regional and

national concern. The information is primarily intended for

those who are involved in water-resource management.

Indeed, this report addresses many of the concerns raised by

regulators, water-utility managers, industry representatives,

and other scientists, engineers, public officials, and members

of stakeholder groups who provided advice and input to the

USGS during this NAWQA Study-Unit investigation. Yet,

the information contained here may also interest those who

simply wish to know more about the quality of water in the

rivers and aquifers in the area where they live.

Knowledge of the quality of the Nation's streams and aquifers is important because of the implications to human

and aquatic health and because of the significant costs associated with decisions involving land and water management, conservation, and regulation. In 1991, the U.S. Congress appropriated funds for the U.S. Geological Survey

(USGS) to begin the National Water-Quality Assessment (NAWQA) Program to help meet the continuing need for

sound, scientific information on the areal extent of the water-quality problems, how these problems are changing

with time, and an understanding of the effects of human actions and natural factors on water-quality conditions.

The NAWQA Program is assessing the water-quality conditions of more than 50 of the Nation's largest river

basins and aquifers, known as Study Units. Collectively, these Study Units cover about one-half of the United States

and include sources of drinking water used by about 70 percent of the U.S. population. Comprehensive assessments

of about one-third of the Study Units are ongoing at a given time. Each Study Unit is scheduled to be revisited every

U.S. Geological Survey Circular 

Robert M. Hirsch, Chief Hydrologist
2 Water Quality in the Upper Snake River Basin, Idaho and Wyoming, 1992–95

SUMMARY OF MAJOR ISSUES AND FINDINGS

ISSUE: Do anthropogenic activities adversely affect

water quality in the upper Snake River Basin? PAGE 6

• Water quality in the upper Snake River Basin is

degraded by a variety of nonpoint and point sources of

pollutants. Basinwide, nonpoint sources account for

about 98 and 99 percent of the total nitrogen and phosphorus, respectively, introduced annually to the upper

Snake River Basin. Nonpoint sources account for most

of the sediment reaching streams in the basin. Primary

nonpoint sources of pollutants in the basin are agricultural activities, confined-animal feeding operations,

rangeland grazing, recreational activities, logging, and

atmospheric deposition.

• Stream-water and ground-water quality in agricultural

areas is affected by pesticide and fertilizer applications

and by crop rotation and tillage practices. Agricultural

areas, which account for 21 percent of the basin area,

are concentrated along the main stem of the Snake

River in the downstream parts of the basin. Agricultural

areas contribute pesticides, nitrogen, and phosphorus to

streams and ground water.

• Primary point sources of pollutants in the basin are

industrial discharges, municipal wastewater-treatment

facilities, and fish farms. Permitted discharges from

these point sources during 1985–90 were about 269 billion gallons per year. Although point sources account

for only a small percentage of the total nitrogen and

phosphorus introduced annually to the upper Snake

River Basin, they discharge directly to streams, where

nitrogen and phosphorus become immediately available for uptake.

ISSUE: Does water use in the basin affect the quality of

the water resources? PAGE 8

• Streamflow regulation and water use for irrigation,

hydroelectric power production, and industry affect the

water chemistry and biological communities of

streams. During the irrigation season, diversions and

irrigation returns reduce streamflows and degrade

stream-water quality. Storage reservoirs for irrigation,

flood control, and hydroelectric power reduce streamflow velocities and stream habitat to the detriment of

native biological communities.

• Irrigated agriculture is the primary consumptive use of

water in the basin. About 8 million acre-feet, or 53 percent, of the water used for irrigation in the basin in

1990 was diverted from surface-water supplies. About

half of these diversions are from five canals at Lake

Walcott and Milner Dam. About 7.1 million acre-feet,

or 47 percent, of the total irrigation use was withdrawn

from ground water. Some water applied to fields for

irrigation returns to streams or infiltrates back to the

ground water, transporting nutrients, pesticides, and

sediment.

• Fish farms and hydroelectric power facilities are the

primary nonconsumptive water uses in the basin. Many

fish farms, primarily along the Snake River between

Milner Dam and King Hill, use ground water discharging from springs as a source of water. Fish farms contribute nitrogen, phosphorus, and organic wastes to

streams. Diversions and impoundments for storage and

hydroelectric power generation alter streamflow

streamflow velocities and transform some reac

the Snake River from a high-gradient, coldwate

to a slow-moving river with an abundance of a

plants.

ISSUE: Have fish communities in the upper Snak

Basin been affected by water-quality degradation

PAGE 10

• There is a large amount of variability in the he

fish communities in the upper Snake River Bas

some streams of the basin, cutthroat, rainbow, 

brown trout fisheries represent some of the bes

in the Nation. In areas of the basin degraded by 

and water-use activities, the entire fish commu

composed of warmwater-tolerant, nongame sp

fish.

• High-elevation headwater streams in the basin 

excellent water quality; however, of the stream

assessed, headwater streams contained the few

and lowest numbers of fish species. In most of 

headwater streams assessed, only two to four d

fish species were found, primarily trout and scu

This lack of species diversity is typical of high

tion headwater streams in the Western United S

where abundant shading and limited nutrient av

ity result in cold, nutrient-poor streams.

• Excellent water-quality conditions, in combina

with stocking of gamefish, make the upper reac

the Henrys Fork and the Snake River upstream 

confluence with the Henrys Fork some of the b

fishing streams in the Nation. These streams su

healthy populations of cutthroat, rainbow, and 

trout, but are dependent on stocking.

• From the confluence of the Snake River and the 

Fork downstream to Milner Dam, the Snake Ri

its tributaries are indicative of trout fisheries af

by loss of habitat and introduction of non-nativ

cies. Fish communities in this reach also have b

affected by nonpoint source inputs of nutrients 

iment and by reductions of streamflows for irri

and hydroelectric power production.

• The Snake River from Milner Dam to King Hi

tains a variety of fish species. However, the rea

reach contains more fish species than do upper 

of the basin is that the community composition 

inated by introduced warmwater species, which 

erant of the slow-moving water and degraded w

quality conditions. Few gamefish exist in this r

the Snake River.

ISSUE: Is nitrate a concern in streams and groun

in the upper Snake River Basin? PAGE 12

• Nitrate concentrations in streams in the upper S

River Basin were generally low, and none exce

U.S. Environmental Protection Agency (USEP

drinking-water standard of 10 milligrams per li

nitrogen. In contrast, some ground-water samp

tained nitrate concentrations in excess of 10 mi

per liter.
U.S. Geological Survey Circu

SUMMARY OF MAJOR ISSUES AND FIN

• The major sources of nitrate in the upper Snake River

Basin are synthetic fertilizers, cattle manure, and nitrogen-fixing legume crops such as alfalfa and beans.

These sources account for 93 percent of the nitrate

input to the basin.

• Nitrate concentrations were less than 2.0 milligrams

per liter in 95 percent of 527 stream samples collected

during the NAWQA study. However, concentrations of

nitrate in many streams were sufficient, in combination

with sufficient phosphorus, to result in excessive

growth of aquatic plants. Nitrate concentrations were

highest in streams draining agricultural areas and in

streams receiving large amounts of ground-water discharge.

• Nitrate concentrations exceeded a national background

level of 3.0 milligrams per liter in water from 25 percent

of 726 wells (mostly domestic and water supply) sampled basinwide during 1991–95. Water in 3 percent of

the wells contained nitrate concentrations in excess of

10 milligrams per liter.

• In localized areas, nitrate in ground water is becoming

a concern. In agricultural areas north of the Snake

River between Burley and Hagerman, water from 10

percent of 105 domestic and irrigation wells sampled

contained nitrate concentrations in excess of 10 milligrams per liter. Water from 24 percent of 29 domestic

wells in a shallow alluvial aquifer in the Minidoka Irrigation District north of Burley contained nitrate concentrations in excess of 10 milligrams per liter.

• Areas where ground water is most vulnerable to nitrate

contamination are those where urban or irrigated agricultural land uses are predominant, where the depth to

water is shallow, and where soils are well drained.

ISSUE: Are pesticides and other organic compounds

reaching streams and ground water? Are they persisting

in the environment? PAGE 14

• Many different pesticides and other organic compounds

are reaching the water resources of the upper Snake

River Basin. Some compounds, primarily those which

have been banned from use, have accumulated in fish

tissue and bed sediment. Although most of the compounds that were detected were at low concentrations,

some compounds were detected at concentrations that

exceeded either drinking-water standards or national

guidelines for the protection of fish-eating wildlife.

• The herbicide EPTC, or Eptam, was detected in 30 of

37 basinwide stream samples collected during May and

June 1994. The maximum concentration of EPTC

detected was 0.31 microgram per liter. Other pesticides

or pesticide breakdown products commonly detected in

streams were atrazine, desethylatrazine, metolachlor,

and alachlor.

• Pesticides in streams were detected in the greatest numbers and largest concentrations during the spring and

early summer following early season crop applications.

However, atrazine and desethylatrazine were detected

in some streams throughout the year.

• None of the pesticide concentrations detected in stream

samples exceeded existing drinking-water standards

established by the USEPA. Two samples from irrigation drains, however, contained the insecticide

rpyrifos and methylazinphos at concentrations

exceeding USEPA aquatic-life criteria.

• At least 1 organochlorine compound was dete

of 20 bed-sediment sampling sites and 16 of 2

sue sampling sites during 1991–94. The most 

monly detected organochlorine compounds we

the DDT breakdown products DDD and DDE

PCBs. Concentrations of organochlorine comp

tissue of fish from the Portneuf River at Pocate

Rock Creek near Twin Falls, and Snake River 

Twin Falls equaled or exceeded national guide

protection of fish-eating wildlife.

• At least 1 semivolatile organic compound (SV

detected in all of the 43 bed-sediment samples 

lected during the study. The most frequently d

SVOCs in bed sediment were phthalates (98 p

the samples), phenol (86 percent), and 2,6-dim

naphthalene (83 percent). However, none of th

concentrations in the bed-sediment samples ex

aquatic-life criteria.

• Some pesticides and volatile organic compoun

(VOCs) also are reaching ground water. Durin

wide sampling in 1994 and 1995, water from 7

domestic, irrigation, stock, and public supply w

percent) contained at least 1 pesticide, and 11 

percent) contained at least 1 VOC. Water from 

wells (13 percent) contained 3 or more pesticid

zine and desethylatrazine were detected in 27 

of the wells.

• Results of a survey of domestic and irrigation 

agricultural lands in the Twin Falls and Burley 

showed that water from 43 of 105 wells (41 pe

contained 3 or more pesticides. None of the pe

concentrations and only one VOC (1,2-dichlor

pane) concentration detected in ground water e

drinking-water standards.

ISSUE: What are the water-quality concerns in t

Snake River between Milner Dam and King Hill

are the primary sources of pollutants? PAGE 18

• The Snake River between Milner Dam and Kin

degraded because of the cumulative effects of 

of agricultural and industrial activities. The de

water quality in the river results from a combi

excessive nitrogen, phosphorus, pesticides, an

ment, and reduced streamflows. Excessive aqu

etation, low dissolved oxygen, and high water

temperatures—all manifestations of a nutrient

eutrophic water body—prevent water in this re

meeting State water-quality criteria.

• Many aquatic species once native to the Snake 

downstream from Milner Dam either have disa

from the reach or are in danger of doing so be

the degraded water quality and streamflow alte

caused by dams.

• Major sources of nutrients to the Snake River 

Milner Dam and King Hill include ground-wa

charge, fish farms, and municipal wastewater-t

facilities. Agriculturally affected tributaries an

tion return flows are sources of additional nutr

are the primary sources of pesticides and sedim
4 Water Quality in the Upper Snake River Basin, Idaho and Wyoming, 1992–95

ENVIRONMENTAL SETTING AND HYDROLOGIC CONDITIONS

LOCATION MAP

115°

114°

113°

112°

44°

43°

111°

110°

44°

43°

113°

112°

111°

110°

42° 42°

115°

114°

King

Hill

Hagerman

Twin

Falls

Pocatello

Idaho

Falls

Milner

Dam

Jackson

Lake

Palisades

Reservoir

American

Falls

Reservoir

Snake

River

Boundary

Yellowstone National Park

Salt

River

Henrys

Fork

River

Teton

River

Snake

River

Blackfoot

River

Portneuf

River

Lost

Big

River

Big Wood Malad

River

Snake

River

IDAHO

WYOMING

IDAHO

NEVADA UTAH

0

0 10

10

20

20

30 40 KILOMETERS

30 40 MILES

Lake

Walcott

Raft

River

Greys

River

Ventre

River

Gros

River

Hoback

Falls River

Mud

Lake River

Lost

Little

Eastern

Plain

River

Snake

10

90

80

70

60

50

40

30

20

10

0

14,000

12,000

10,000

8,000

6,000

4,000

2,000

0

WATER WITHDRAWALS,

IN MILLIONS OF

GALLONS PER DAY

Ground

 water

Surface

 water

Population

 served, in

 thousands

Total

Public supply

Domestic supply

Irrigation and

livestock

(299)

(299)

(101)

ESTIMATED WATER

WITHDRAWALS IN 1990

55

50

45

40

35

30

25

20

15

10

5

0

20,000

18,000

16,000

14,000

12,000

10,000

8,000

6,000

4,000

2,000

0

AREA, IN SQUARE MILES

TOTAL AREA =

35,800 

SQUARE MILES

PERCENT OF TOTAL AREA

Rangeland

Forested land

Agricultural land

Other

LAND USE IN 1986

LAND-USE MAP

0

0 10

10

20

20

30 40 KILOMETERS

30 40 MILES

115°

114°

113°

112°

44°

43°

111°

1

43°

113°

112°

111°

42° 42°

115°

114°

King

Hill

Twin

Falls

Pocatello

Idaho

Falls

Jackson

Lake

Palisades

Reservoir

American

Falls

Reservoir

Snake

River

Henrys

Fork

River

Snake

River

Portneuf

River

Lost

Big

River

Big

Wood

Snake

River

IDAHO

WYOMING

IDAHO

NEVADA UTAH

Eastern

Plain

River

Snake

Shoshone Falls

Burley

Rexburg

Rock

Creek

Buhl

streams and ground water in the upper Snake River Basin. Five main-stem and numerous tributary reservoirs regulate streamflow in t

primarily for agricultural use, flood control, and hydroelectric power production. The major source of ground water in the basin is the fr

basalt aquifer underlying the eastern Snake River Plain. In 1990, about 53 percent of the water used in the upper Snake River Basin w

drawn from surface-water supplies and 47 percent from ground water, primarily for irrigation and livestock.

About 18,000 square miles, or about 50 percent, of the upper Snake River Basin is rangeland; forested land and agricultural land 

23 and 21 percent of the basin, respectively. Forested land is located primarily in the mountainous eastern part of the basin where pre

is the greatest. Agricultural land is concentrated on the Snake River Plain, primarily along the Snake River and near the mouths of tribu

age basins.

Climate in the upper Snake River Basin is

influenced predominantly by eastward-moving

airmasses from the Pacific Ocean. The semiarid

eastern Snake River Plain receives 8 to 10

inches of precipitation annually. The semihumid

mountainous parts of the basin receive the

greatest amount of precipitation as snow, generally between November and March. Mountains

in the northeastern part of the basin may

receive more than 60 inches of precipitation

annually.

The Snake River is the regional drainage for
U.S. Geological Survey Circu

ENVIRONMENTAL SETTING AND HYDROLOGIC COND

Stream discharges in the upper Snake River Basin during water years 1992–95 were largest during May and June in response to 

snowmelt in mountainous areas of the basin. However, stream discharge at the outlet of the basin was relatively stable throughout th

because of reservoir regulation and the large quantity of ground water discharged to the river as springs between Milner Dam and Ki

Large stream discharges in response to individual storms were rare during the study.

In the northern and eastern parts of the basin, hydrologic conditions were wetter than normal, and stream discharges larger than 

averages during water years 1993 and 1995. The opposite was true during water years 1992 and 1994—conditions were drier than no

stream discharges were below average throughout the basin. In the southern part of the basin and in the main-stem Snake River, str

charges were smaller than long-term averages during all 4 years of the study. MEAN DISCHARGE, IN CUBIC FEET PER SECOND

20,000

15,000

10,000

5,000

0

Oct.

Dec.

Feb.

Apr.

Nov.

Jan.

Mar.

May

June

July

Aug.

Sept.

WATER YEARS 1992–95

12,000

9,000

6,000

3,000

0

1983–95

Snake River at King Hill, Idaho

1992199319941995

MEAN DISCHARGE, IN

CUBIC FEET PER SECOND

1,200

1,000

800

600

400

200

0

Oct.

Dec.

Feb.

Apr.

Nov.

Jan.

Mar.

May

June

July

Aug.

Sept.

WATER YEARS 1992–95

500

400

300

200

100

0

1910–95

Big Lost River near Chilly, Idaho

1992199319941995

MEAN DISCHARGE, IN

CUBIC FEET PER SECOND

5,000

4,000

3,000

2,000

1,000

0

Oct.

Dec.

Feb.

Apr.

Nov.

Jan.

Mar.

May

June

July

Aug.

Sept.

WATER YEARS 1992–95

3,000

2,000

1,000

0

1909–95

Henrys Fork near Rexburg, Idaho

1992199319941995

Snake River at Flagg Ranch, W

MEAN DISCHARGE, IN

CUBIC FEET PER SECOND

3,500

3,000

2,500

2,000

1,500

1,000

500

0

Oct.

Dec.

Feb.

Apr.

Nov.

Jan.

Mar.

May

June

J

WATER YEARS 1992–

1,000

800

600

400

200

0

1983–95

1992199319941995

IDAHO

WYOMING

IDAHO

NEVADA UTAH

Yearly mean discharge, 1992–95

Mean monthly discharge, 1992–95

Mean discharge, beginning period

 of record to 1995

EXPLANATION

MEAN DISCHARGE, IN

CUBIC FEET PER SECOND

8,000

6,000

4,000

2,000

0

Oct.

Dec.

Feb.

Apr.

Nov.

Jan.

Mar.

May

June

July

Aug.

Sept.

WATER YEARS 1992–95

6,000

4,000

2,000

0

1910–95

Snake River near Blackfoot, Idaho

1992199319941995

Portneuf River at Topaz, Idaho 300

250

200

150

100

50

0

Oct.

Dec.

Feb.

Apr.

Nov.

Jan.

Mar.

May

June

J

WATER YEARS 1992–

250

200

150

100

50

0

1992199319941995

1919–95

MEAN DISCHARGE, IN

CUBIC FEET PER SECOND
6 Water Quality in the Upper Snake River Basin, Idaho and Wyoming, 1992–95

MAJOR ISSUES AND FINDINGS

DO ANTHROPOGENIC ACTIVITIES ADVERSELY

AFFECT WATER QUALITY IN THE UPPER SNAKE

RIVER BASIN?

Water quality in the upper Snake River Basin is degraded

by numerous anthropogenic activities, including both nonpoint and point sources of pollutants. A 1988 assessment by

the Idaho Department of Environmental Quality documented

that, of 5,732 river miles assessed for nonpoint source effects

in the Idaho part of the basin, 2,913 river miles were

degraded by agriculture; 1,766 miles by hydrologic modification; 197 miles by construction activities; 35 miles by forest practices; 134 miles by mining; and 109 miles by other

activities, primarily recreation [1]. Other nonpoint sources of

pollutants in the basin include beef and dairy cattle feeding

operations, atmospheric deposition, and rangeland grazing.

These nonpoint sources contribute sediment, bacteria, nutrients, and pesticides to streams and can result in alterations in

stream habitat and water temperature. Primary point sources

in the upper Snake River Basin include industrial discharges,

municipal wastewater-treatment facilities, and fish farms.

Permitted discharges from these point sources during 1985–

90 were about 269 billion gallons per year [2]. Primary pollutants associated with point sources include nitrogen, phosphorus, and organic wastes.

than 1 percent of the basin area. The geographic dist

of these land-use/land-cover categories has a large e

the quality of water in the basin. Primary land uses a

cover in the mountainous northern and eastern parts 

basin are forested land and rangeland, and although 

practices and grazing may degrade water quality, wa

resources and the aquatic biological communities in 

areas are generally of high quality. In contrast, agric

activities, urban communities, and industries concen

on the Snake River Plain, primarily along the Snake 

and near the mouths of major tributary valleys, contr

sediment, fertilizers, organic compounds, and other 

ants to the Snake River and its tributaries [3,4]. As a 

quence, stream- and ground-water quality and biolo

communities in the downstream parts of the upper S

River Basin have been degraded by anthropogenic a

[4,5,6].

The Snake River near Idaho Falls, Idaho. The agricultural industry in

southern Idaho is dependent on the Snake River and its tributaries

for its water supply (photograph © 1978 by W.H. Mullins and published with permission).

Recreation in the upper Snake River Basin has become inc

popular, primarily in Wyoming and in the Henrys Fork Basi

stone and Grand Teton National Parks in Wyoming attract n

million visitors a year (photograph by M.G. Rupert, U.S. Ge

Survey).

The types and geographic distribution of land use and land

cover, the types and numbers of industries and municipalities

using the water resources, and the manner in which the water

resources are used are factors that create the water-quality

conditions in the upper Snake River Basin as described in

this report. Approximately 18,000 square miles of rangeland

compose roughly one-half of the basin area. Forested and

agricultural lands compose 23 and 21 percent, respectively,

of the upper Snake River Basin. Urban areas compose less

About 71 perce

Idaho’s crops a

duced in the up

Snake River Ba

mary crops inc

toes, beans, su

alfalfa, and gra

graph © 1976 b

Mullins and pu

with permission

A large part of Idaho’s economy relies on irrigate

culture, which subsequently relies on adequate supp

water. In 1990, 71 percent of all irrigated acreage in 

was in the upper Snake River Basin, where potatoes

wheat, sugar beets, alfalfa, and barley are the predom

crops [2]. These agricultural lands are areas where p
U.S. Geological Survey Circula

MAJOR ISSUES AND FIN

and fertilizer applications and crop rotation and tillage practices degrade stream and ground-water quality. Although

crop yields are improved by applications of fertilizers and

pesticides, the increased production often comes at the

expense of water quality.

Streamflow regulation in the upper Snake River Basin for

irrigation and hydroelectric power production has a detrimental effect on the water chemistry and biology of streams.

During the irrigation season (April to October), much of the

water in streams is diverted to canals for irrigation needs.

These diversions reduce streamflows, to the detriment of the

biological communities [6,7]. Fifteen large hydroelectric

power facilities, generating about 1.2 million megawatthours

of electricity annually, and numerous smaller facilities provide a large percentage of Idaho’s electrical output [2].

Although hydroelectric power facilities generally do not produce pollutants, the dams, diversions, and canals associated

with the facilities commonly change streamflow characteristics and alter habitat conditions for various species of aquatic

organisms [7].

Since 1980, the number of beef and dairy cattle in the

basin has grown substantially [8]. Beef and dairy cattle operations (confined-animal feeding operations) discharge some

pollutants directly to streams; however, their wastes have a

larger effect on ground-water quality [9]. In many areas

where the cattle industry is growing, nitrate concentrations in

ground water are already high because of fertilizer applications and manure production. Pollutants reaching ground

water in the upper Snake River Basin eventually return to the

Snake River, providing additional nitrogen and phosphorus

to many streams where eutrophication problems are already

evident [3,4].

Although urban areas compose less than 1 percent of the

basin area, they are a potential source of pollutants to

streams and ground water. Major urban areas in the basin are

Idaho Falls, Pocatello, Rexburg, and Twin Falls, which

together account for about 30 percent of the total basin population. These four cities discharge nearly 7.5 billion gallons

of treated wastewater annually to the Snake River and its

tributaries [2]. Areas in the Wyoming part of the basin do not

have a large resident population but do have a signifi

influx of people each summer because of tourism an

ational opportunities. In 1990, nearly 3 million peop

ited the Grand Teton and Yellowstone National Park

some parts of the basin, the population is expected t

substantially in the future. Projections indicate that b

the population in the basin will reach 480,000, a 20-

increase from the 1980 population [2]. An increasin

lation will put increasing pressure on the quantity an

ity of the water resources in the basin. Urban runoff 

potential to transport fertilizers, organic compounds

trace elements from streets, parking lots, and lawns 

streams and ground water. Fish-tissue and bed-sedim

samples collected downstream from urban areas dur

National Water-Quality Assessment (NAWQA) stud

tained some of the largest concentrations of organic 

pounds in the basin [10].

Numerous dams, like this one on Jackson Lake in Grand Te

National Park, provide storage for downstream water needs

the dams in the upper Snake River Basin also are used to g

hydroelectric power (photograph © 1995 by W.H. Mullins an

lished with permission).

The growth in the number of confined-animal feeding operations has

become a concern in parts of the basin. Animal wastes can pollute

streams and ground-water supplies (photograph © 1995 by W.H.

Mullins and published with permission).

Although point sources of pollutants account for 

about 2 and 1 percent of the total nitrogen and phosp

respectively, introduced annually to the upper Snake 

Basin [3], they typically discharge directly to stream

pollutants become immediately available for uptake. 

point sources of pollutants in the basin are industrial 

charges, municipal wastewater-treatment facilities, a

farms. Three industrial facilities, 13 wastewater-trea

facilities, and 12 fish farms are permitted to release 2

lion gallons of effluent in the upper Snake River Bas

ally [2]. In addition, numerous other smaller, unperm

point sources of pollutants exist in the basin. Of the 

charge from point sources, about 95 percent is from 

farms; most of the water passing through the fish far

supplied by springs downstream from Milner Dam. W

ter-treatment facilities account for only about 4 perce

total point source discharge in the basin [2]. Howeve

water-treatment effluent is typically more enriched i

gen, phosphorus, and organic wastes than is the efflu

fish farms and, in some areas of the basin, accounts 

proportionate amount of the pollutants entering strea
8 Water Quality in the Upper Snake River Basin, Idaho and Wyoming, 1992–95

MAJOR ISSUES AND FINDINGS

DOES WATER USE IN THE BASIN AFFECT THE

QUALITY OF THE WATER RESOURCES?

The Snake River often is referred to as a working river

because of its highly regulated streamflow. Five reservoirs on

the main stem of the Snake River have a combined storage

capacity of more than 4 million acre-feet, and eight reservoirs on Snake River tributaries have storage capacities of

more than 50,000 acre-feet each [11]. Numerous dams and

diversions, primarily for irrigation and hydroelectric power

generation, have resulted in smaller streamflows and streamflow velocities, alterations in biological communities, and

growth of nuisance aquatic plants. Other water uses in the

upper Snake River Basin are domestic and public supply, fish

farms, and confined-animal feeding operations. Inputs of

nutrients, organic wastes, and other pollutants from these

sources have degraded the water quality in many streams in

the upper Snake River Basin.

In 1990, water use in Idaho totaled 22 million acre-feet

(about 20,000 million gallons per day), ranking third in the

Nation behind California and Texas. Of this total, nearly 70

percent was used in the upper Snake River Basin [2]. Use of

surface water and ground water in the basin was about

equal—about 8 million acre-feet (7,100 million gallons per

day) was diverted from surface-water supplies, and about 7.1

million acre-feet (6,300 million gallons per day) was withdrawn from ground-water supplies [2].

Most of the economy in the upper Snake River Basin is

dependent on industries that require ample sources of highquality water. Currently, the largest water uses in the basin

are irrigated agriculture, food processing and other industries, public supply, fish farms, and hydroelectric power

facilities [2]. Irrigated agricultural, industrial, and public

supply water uses are partially consumptive in that water is

withdrawn from the source, transported to the point of use,

and at least partially consumed. Fish farms and hydroelectric

power facilities are nonconsumptive uses because all the

water used is returned to streams.

About half of the total surface-water diversions in the

upper Snake River Basin are from five canals at Lake Walcott and Milner Dam for irrigation of about 575,000 acres of

agricultural land [12]. Some of the water applied to fields for

irrigation infiltrates to the ground water or returns to 

by way of canals, also transporting sediment, fertili

pesticides [4]. Because of diversions, streamflows in 

Snake River often are reduced substantially during m

months of the year. Low streamflows, combined wit

instream reservoirs, have transformed some reaches 

Snake River from a high-gradient, coldwater river to 

moving, warmwater river supporting primarily nong

cies of fish [6].

In 1990, domestic and public supply systems pro

less than 150,000 acre-feet (130 million gallons per 

Diversion canals, like this one at American Falls Reservoir, supply

irrigation water for large tracts of land adjacent to the Snake River in

Idaho. In 1990, about 8 million acre-feet of water was diverted from

streams in the basin to irrigate about 4.7 million acres of agricultural

land (photograph by G.M. Clark, U.S. Geological Survey).

Diversions of w

the Snake Rive

large effect on s

discharge. Shos

Falls on the Sna

near Twin Falls

an impressive s

during high stre

discharge. Duri

irrigation seaso

however, discha

the falls can be 

to a mere trickle

(photographs by 

Clark, U.S. Geo

Survey).

Streamflow in the Snake River during the nonirrigation sea

ary, for example) is typical of an unregulated stream—stre

increases with downstream distance. During the irrigation 

(August, for example), streamflow in the Snake River fluctu

stantially over its length in response to diversions, irrigatio

flows, and ground-water discharge.

Palisades

Dam

Th

S

American

Falls Dam

Henrys

Fork

Milner

Dam

Minidoka

Dam

12,000

10,000

8,000

6,000

4,000

2,000

0

STREAMFLOW, IN CUBIC FEET PER SECOND

900 800 700 600 

RIVER MILES FROM MOUTH (OUTLET)

OF THE SNAKE RIVER

Mean monthly streamflow, 1980–95

January

August
U.S. Geological Survey Circula

MAJOR ISSUES AND FIN

water to about 400,000 people in the upper Snake

River Basin. More than 80 percent of this water was

derived from ground-water supplies. Domestic and

public supplies accounted for less than 1 percent of

the total basin water use [2]. However, as the population in the basin continues to grow, the demand for

high-quality water for domestic and public supplies

will grow accordingly.

Fish farms and hydroelectric power facilities are

the primary nonconsumptive water uses in the basin.

Fish farms along the Snake River between Milner

Dam and King Hill used about 2,500 cubic feet per

second of ground-water discharge as source water in

1995 [4]. When water passes through a fish farm, it

becomes enriched with nitrogen, phosphorus, and

suspended sediments, which eventually are discharged to the Snake River [4].

As available surface-water supplies have diminished, use of ground water in the upper Snake River

Basin has increased substantially. From 1980 to

1990, annual ground-water use in the basin

increased from 2.6 million acre-feet (2,300 million

gallons per day) to 7.1 million acre-feet (6,300 million gallons per day) [2]. In 1980, ground water accounted for only

22 percent of the total basin water use. In 1990, ground water

accounted for about 47 percent. As a result, ground-water

levels in some areas of the basin have declined since 1980

[5,13]. Although most of the increase in ground-water use

has been for irrigated agriculture, the number of confinedanimal feeding operations in the lower parts of the basin that

rely on ground-water supplies has been increasing rapidly

[8]. In some areas of the basin where agriculture and confined-animal feeding operations are prominent, small conHistorically, furrow irrigation has been

the primary method of watering crops.

Excess irrigation water either

infiltrates to underlying aquifers or

returns to streams (photograph by

M.A. Maupin, U.S. Geological

Survey).

Ground water has beco

increasingly important s

agricultural and domes

needs. In 1990, 47 per

the water used in the b

supplied by ground wa

(photograph by M.G. R

U.S. Geological Survey

Total discharge from springs along the north side of the Snake River

from Milner Dam to King Hill reflects historical changes in water-use

patterns. Spring discharge increased substantially from the early

1900’s to the late 1950’s in response to an increase in ground-water

recharge from surface-water irrigation. A general decline in discharge

since the mid- to late 1950’s is attributable to an increase in groundwater pumpage for irrigation and other purposes.

Streamflow diversions for other uses can result in warmer w

perature, which is detrimental to most native species of fish

Snake River at Flagg Ranch, Wyoming, a site with natural h

conditions, even during the warmest period of the year (Aug

temperature criterion of 19 degrees Celsius is rarely exceed

ever, at the Malad River near Gooding, Idaho, a site affected 

sions, the temperature criterion is often exceeded during th

month of August.

centrations of pesticides and nitrate concentrations

exceeding the U.S. Environmental Protection Agenc

(USEPA) drinking-water standard of 10 milligrams p

have been detected in water from domestic wells [5,

7,000

6,500

6,000

5,500

5,000

4,500

DISCHARGE, IN CUBIC FEET PER SECOND

4,0001900 1940 1960 1980 1995

WATER YEAR

Total annual discharge from

springs on the north side

of the Snake River from

Milner Dam to King Hill

1920

260

240

220

200

180

160

DISCHARGE, IN CUBIC FEET PER SECOND

1 5 10 30

AUGUST 1994

Coldwater biota

maximum daily average

temperature criterion

Malad River near Gooding, Idaho

Snake River at Flagg Ranch, Wyoming

100

80

60

40

20

0

15 20 25

Water

temperature Discharge

Water

temperature

Discharge

Coldwater biota

maximum daily average

temperature criterion
10 Water Quality in the Upper Snake River Basin, Idaho and Wyoming, 1992–95

MAJOR ISSUES AND FINDINGS

HAVE FISH COMMUNITIES IN THE UPPER SNAKE

RIVER BASIN BEEN AFFECTED BY WATERQUALITY DEGRADATION?

A large amount of variability exists in the health of fish

communities in the upper Snake River Basin. In some

streams of the basin, cutthroat, rainbow, and brown trout

fisheries represent some of the highest quality fishing in the

Nation. In other areas of the basin, where streams have been

degraded by land- and water-use activities, the fish community is composed of warmwater-tolerant, nongame species.

Because trout species generally require cold water temperatures and ample dissolved oxygen for survival, trout species

have been nearly eliminated in several degraded streams of

the basin [6,7].

the quality of fish communities in the Snake River a

tributaries deteriorates from the headwaters of the S

River near Yellowstone National Park to the basin o

King Hill. The notable exception to this trend is in R

Creek near Twin Falls, where fish stocking and the i

sediment-free ground water results in a fish commun

better quality than that of many upstream sites.

A common perception about fish communities is 

greater the number of fish species and the greater the 

of total fish, the better the stream-water quality. Usu

diverse community with many species indicates goo

quality. Polluted water, on the other hand, generally 

fewer species, many of which can tolerate pollution 

create rapidly. Although this perception may be true 

areas of the Nation, it is not necessarily true for fish 

nities in coldwater streams of Idaho and Wyoming [

In the upper Snake River Basin, high-quality strea

high elevations usually contain fewer fish species th

streams at lower elevations [6]. Many headwater stre

might have been devoid of fish prior to the introduct

selected species for sportfishing. Coldwater streams 

ally do not offer the food sources, temperature, and 

features that many fish species prefer. Fish commun

pling during the NAWQA study and historical data f

upper Snake River Basin indicate that relatively sma

turbed headwater streams in northern, eastern, and s

parts of the basin tend to contain the fewest fish and 

est number of species. Numerous small reference (le

turbed by human activities) streams in the basin cont

average of only 2 to 4 fish species and less than 100 t

in the reaches sampled. In most of the reference stre

sampled, only native or introduced trout and sculpin 

present. In contrast, streams with degraded water qu

contained between 5 and 10 different fish species and 

numbers of fish than reference streams contained. Fi

munities in degraded streams were predominantly in

duced, nongame species tolerant of degraded water-

conditions.

Fishing enthusiasts from all parts of the Nation enjoy the high-quality

fisheries in some headwater areas of the upper Snake River Basin.

Large cutthroat, rainbow, and brown trout, like this one caught from

the Henrys Fork, are typical of fish communities in the Henrys Fork

and the Snake River upstream from its confluence with the Henrys

Fork. Although healthy trout populations once existed in all parts of

the basin, today they are located primarily in pristine headwater areas

of the basin (photograph © 1996 by W.H. Mullins and published with

permission).

Characterization of fish communities in streams and reservoirs is a useful tool for assessing effects of land- and wateruse activities on water-quality conditions because fish are sensitive to a large array of stresses, many species of fish are

widely distributed, and descriptive analyses of fish communities are easy to understand. Fish are also relatively long-lived,

and they integrate adverse effects of stresses in the aquatic

community. In addition, Idaho water-quality standards designate aquatic biota and salmonid spawning as beneficial uses of

many streams in the State and, as a result, water-quality criteria have been established to protect instream fisheries. Specific

areas of concern include input of chemical pollutants, loss of

instream habitat, sedimentation of spawning beds, decreased

streamflows, increased water temperatures, and introduction

of non-native species [7].

Overall, 26 native and 13 introduced fish species representing numerous different fish families were collected in the

basin during the NAWQA study. About 73 percent of the species collected from all sites were native [6]. An Index of Biotic

Integrity derived from NAWQA data indicates that, in general,

NAWQA scientists assess fish communities using electrofis

niques. Most fish collected are catalogued and released. S

however, are collected and sent to laboratories where their 

analyzed for the presence of pollutants (photograph by T.R

U.S. Geological Survey).
U.S. Geological Survey Circula

MAJOR ISSUES AND FIN

The upper reaches of the Henrys Fork and the Snake River

upstream from its confluence with the Henrys Fork represent

two of the best large-river trout fisheries in the Nation. Cutthroat, rainbow, and brown trout make up most of the game

species in these stream segments. Nongame species are primarily native sculpin and suckers. Rainbow and brown trout,

introduced to enhance the sportfishery, make up most of the

non-native species in the upper reaches of the Henrys Fork

and the Snake River upstream from the confluence.

Downstream from the confluence of the Snake River and

Henrys Fork to Milner Dam, fish communities in the Snake

River and its major tributaries are composed primarily of

cutthroat trout and other native and non-native species [7].

However, fish communities in this reach have been degraded

by the cumulative effects of irrigation return flows, grazing,

and diversions. Sediment from bank erosion and irrigation

return flows has blanketed stream bottoms and caused loss of

suitable spawning habitat. Reservoirs and irrigation 

sions in the reach also have resulted in reduced stre

flows, degraded water-quality conditions, loss of ha

and proliferation of non-native, warmwater species 

[7].

Historical information indicates that, prior to hyd

tric power development, numerous native, ocean-mi

species inhabited the Snake River from Shoshone Fa

the city of Twin Falls downstream to the basin outle

King Hill. Species included chinook salmon, steelh

Pacific lamprey, and white sturgeon [7]. Of these sp

only the white sturgeon is still present in the reach, 

population is declining and is sparsely distributed. F

community assessments conducted during the NAW

study indicate that this reach of the Snake River is c

posed predominantly of nongame species such as c

suckers [6]. The presence of a fish community dom

by carp and suckers is attributable to reduced stream

large inputs of nutrients and fine-grained sediment, 

sive aquatic plant growth, and elevated water tempe

Temperatures in excess of 19 degrees Celsius (the m

mum criterion for coldwater biota) and dissolved-o

concentrations as small as 1.0 milligram per liter ha

measured [7]. Because of the degraded water qualit

have been nearly eliminated in the reach of the Snak

between Shoshone Falls and King Hill.

In many parts of the upper Snake River Basin, especially in the

lower reaches, pollution-tolerant, warmwater species like this common carp dominate the fish community. Trout and other coldwater

species of fish cannot tolerate the degraded conditions in some

streams of the basin (photograph © 1991 by W.H. Mullins and published with permission).

At one time, white

sturgeon, like this

630-pounder

caught in 1908,

were common in

the Snake River

downstream from

Shoshone Falls.

Some sturgeon

still survive in the

reach; however,

because of reduction in the available habitat and

poor water-quality

conditions, their

sizes and numbers have dwindled compared

with the historical

population (photograph courtesy of

the Idaho Historical Society).

Comparison of fish community indexes for the main-stem 

River and major tributary sites. The higher the fish commu

the higher the quality of the fish community. Index scores a

to the best fishery condition (Snake River at Flagg Ranch, 

and are based on percent introduced species, percent ano

percent omnivores, and percent tolerant fish species.

Reference

condition

120

100

80

60

40

20

0

FISH COMMUNITY QUALITY AS

PERCENT OF REFERENCE CONDITION

1,100 900 700 600 

RIVER MILES FROM MOUTH (OUTLET)

OF THE SNAKE RIVER

Flagg

Ranch

1,000 800

Minidoka

Salt

River

Portneuf

River

Rock

Creek

Buh

Henrys

Fork Blackfoot

Mai

Trib

Outlet at

Yellowstone

National Park

Milner

Dam

American

Falls

Dam

Shosho

Falls
12 Water Quality in the Upper Snake River Basin, Idaho and Wyoming, 1992–95

MAJOR ISSUES AND FINDINGS

IS NITRATE A CONCERN IN STREAMS AND

GROUND WATER IN THE UPPER SNAKE RIVER

BASIN?

On the basis of data collected during the NAWQA study,

nitrate concentrations in streams in the upper Snake River Basin

were generally low, and none exceeded the USEPA drinkingwater standard of 10 milligrams per liter. However, in some

streams of the basin, nitrate was a contributing factor to the

overabundance of aquatic plants. In contrast to stream samples,

some ground-water samples contained nitrate concentrations in

excess of 10 milligrams per liter. Nitrate contamination in

streams and ground water may become a more serious problem

in the future as population growth and industrial development in

the basin continue.

Nitrate (NO3) is, in general, the predominant form of nitrogen in streams and ground water. Nitrate is highly soluble in

water, stable over a wide range of environmental conditions, and

readily transported in streams and in ground water. Nitrate is

common in the environment; rainwater contains small concentrations. Although nitrate is an essential plant nutrient, in large

concentrations it can be a pollutant in water. Excessive nitrate in

streams, in combination with other nutrients, can lead to overabundance of aquatic plants and degraded water-quality conditions. Large concentrations of nitrate in drinking water also

have been identified as the cause of blue-baby syndrome in

infants, which is characterized by a reduced capacity of the

blood to carry oxygen. Nitrate also has been associated with a

high incidence of non-Hodgkin’s lymphoma and miscarriages

[5,15]. Because of the health concerns associated with nitrate,

the USEPA established the current drinking-water standard of

10 milligrams per liter for nitrate as nitrogen.

The major sources of nitrate in the upper Snake Riv

are fertilizers, cattle manure, and legume crops. These 

sources contribute about 93 percent of the nitrate input 

basin [9]. Precipitation contributes an additional 6 perc

nitrate input to the basin. Domestic septic systems cont

less than 1 percent; however, in densely populated area

domestic septic systems can contribute substantial amo

nitrate to ground water [9].

In most areas of the Nation, nitrate concentrations in 

are not as large as in ground water and rarely exceed th

ing-water standard [16]. This is also true in the upper S

River Basin, where concentrations of nitrate were less 

milligrams per liter in 95 percent of 527 stream sample

lected during the NAWQA study [4]. However, concen

of nitrate in many streams were sufficient, in combinat

sufficient phosphorus and a suitable substrate, to result 

overabundance of aquatic plants, particularly in the dow

reaches of the Snake River.

At 19 stream sites sampled during 1992 through 199

part of the NAWQA and 7 as part of other U.S. Geolog

vey water-quality studies), concentrations of nitrate wer

downstream from agricultural areas. Samples collected 

stem and tributary sites between Milner Dam and King 

tained the largest concentrations of nitrate [4]. Nitrate c

trations in samples collected from the Snake River at K

during the 16-year period from 1980 through 1995 sho

upward or downward trend. Concentrations of nitrate a

Hill were smallest when streamflows were larger than n

Nitrogen fertilizer is

applied to crops to

enhance production. It is

generally added to irrigation water prior to field

application. Excess irrigation water can carry

nitrate to underlying

ground water or back to

streams (photographs by

M.G. Rupert, U.S. Geological Survey).

and largest when streamflows were smaller than norma

charge of ground water to the Snake River from numer

springs between Milner Dam and King Hill is a consta

of nitrate to the river during most years, accounting for 

to 80 percent of the nitrate leaving the upper Snake Riv

at King Hill [4,17]. Nitrate in spring water is derived p

from fertilizers, cattle manure, and legume crops [9].

Cattle manure, which contributes about 30 percent

of the nitrogen annually

introduced to the basin, is

used as a fertilizer on

crops. Manure may

become an even larger

source of nitrogen in the

future as the dairy and

beef cattle industries in the

basin expand (photograph

by M.G. Rupert, U.S. Geological Survey).

Concentrations of nitrate in ground water are increasing in area

upper Snake River Basin. Water from four wells in the shallow 

depth of 40 feet) alluvial aquifer in the Minidoka Irrigation Distr

Burley, Idaho, shows an increase in nitrate concentrations sinc

NITRATE CONCENTRATION, IN MILLIGRAMS PER LITER

9

8

7

6

5

4

3

2

Well location

Latitude – 42° 34' 50" Longitude – 113° 52' 09"

Well location

Latitude – 42° 37' 11" Longitude – 113° 54' 26

Well location

Latitude – 42° 37' 47" Longitude – 113° 55' 50"

Well location

Latitude – 42° 38' 15" Longitude – 113° 55' 01

9

8

7

6

5

4

3

2

1985 1987 1989 1991 1993 1995 1985 1987 1989 1991 

Best-fit line
U.S. Geological Survey Circula

MAJOR ISSUES AND FIN

In 1992, the USEPA reported that nitrate was a principal

ground-water pollutant in 49 States [16]. In the upper Snake

River Basin, elevated nitrate concentrations in ground water

were detected in numerous counties, primarily on the Snake

River Plain [13]. Nitrate concentrations exceeded the 10 milligrams per liter drinking-water standard in water from wells at

the Idaho National Engineering and Environmental Laboratory,

in the Fort Hall area north of Pocatello, and in agricultural areas

north of the Snake River between Burley and Hagerman [5].

Concentrations in 25 percent of 726 wells (mostly domestic and

public supply) sampled basinwide from 1991 through 1995 as

part of the NAWQA and other USGS water-quality studies

exceeded 3.0 milligrams per liter. Concentrations in only 3 percent of the samples exceeded the drinking-water standa

However, in some areas of the basin, nitrate in ground 

becoming a serious concern. In agricultural areas north 

Snake River between Burley and Hagerman, water from 

cent of 105 wells sampled during the NAWQA study, ra

depth from 10 feet to more than 500 feet, contained co

tions of nitrate in excess of 10 milligrams per liter [5]. 

from 24 percent of 29 domestic wells sampled in the sh

(mean well depth of 40 feet) alluvial aquifer in the Min

Irrigation District north of Burley contained nitrate con

tions in excess of 10 milligrams per liter. In the A&B I

District north of Burley, nitrate concentrations in water 

percent of 31 wells sampled (mean well depth of 230 f

exceeded 10 milligrams per liter. In some agricultural a

concentrations of nitrate have increased substantially s

early 1980’s [5]. If the current rate of increase continue

concentrations in a large part of the A&B Irrigation Di

ground-water supply may exceed the 10 milligrams per 

drinking-water standard early in the 21st century [5].

On the basis of data collected during the NAWQA s

probability maps were developed to identify areas in th

Snake River Basin where the potential for ground-wate

ination by nitrate is high. Results indicate that the mos

ble areas are those where urban or irrigated agricultural 

are predominant, where the depth to water is shallow, a

soils are well drained. Other studies across the Nation a

that land-use and soil-drainage characteristics markedl

ence the concentration of nitrate in ground water [18]. 

upper Snake River Basin, ground water beneath agricu

lands adjacent to the Snake River, especially near Burl

Twin Falls, and between Idaho Falls and Pocatello is pa

vulnerable to nitrate contamination [5].

Ground-water samples collected during 1991–95 indicate that n

centrations were largest in wells less than 200 feet deep. None 

ples collected from wells deeper than 500 feet contained nitrate 

trations in excess of the drinking-water standard of 10 milligram

Samples collected during the NAWQA study show that median concentrations of nitrate in the Snake River and at the mouths of major Snake

River tributaries upstream from Milner Dam were all less than 1.0 milligram per liter. Downstream from the dam, however, median nitrate concentrations increased substantially in response to large inflows of nitrateenriched ground water, effluent from industrial and wastewater-treatment

facilities, and irrigation return flows.

60

50

40

30

20

10

0

NITRATE CONCENTRATION,

IN MILLIGRAMS PER LITER

0 200 600 800 400 

WELL DEPTH, IN FEET BELOW LAND SURFACE

Probability maps are valuable for determining areas potentially vulnerable to ground-water contamination. This map

for nitrate, produced during the NAWQA study and based

on depth to ground water, soil characteristics, and land

use, shows that ground water near the Snake River

between Idaho Falls and the outlet of the basin at King Hill

is the most vulnerable to nitrate contamination.

2.0

1.5

1.0

0.5

0

NITRATE CONCENTRATION,

IN MILLIGRAMS PER LITER

1,100 1,000 800 700 900 500 600

RIVER MILE FROM MOUTH (OUTLET)

OF THE SNAKE RIVER

Main stem

Tributary

Outlet at

Yellowstone

National Park

Milner

Dam

Basin

outlet

American

Falls

Dam

Shoshone

Falls

PROBABILITY OF NITRATE

CONTAMINATION

EXPLANATION

0

0 20

20

40 KILOMETERS

40 MILES

115°

114°

113°

112°

44°

43°

111°

110°

44°

43°

113° 112°

111°

110°

42° 42°

115°

114°

King

Hill

IDAHO

NEVADA UTAH

IDAHO

WYOMING

Twin

Falls

Pocatello

Idaho

Falls

Snake

River

Snake

River

Low

Not delin-

 eated

Very high

High

Medium

Burley
14 Water Quality in the Upper Snake River Basin, Idaho and Wyoming, 1992–95

MAJOR ISSUES AND FINDINGS

ARE PESTICIDES AND OTHER ORGANIC

COMPOUNDS REACHING STREAMS AND

GROUND WATER? ARE THEY PERSISTING

IN THE ENVIRONMENT?

Use of pesticides and other organic compounds in many

parts of the Nation poses a potential for serious nonpoint

source contamination of streams and ground water. More

than 1.1 billion pounds of pesticides is used each year in the

United States [19]. In addition, new pesticides are continually being formulated and introduced to improve safety and

minimize adverse environmental effects. As part of the

NAWQA study, samples from streams, bed sediment, fish

tissue, and ground water were collected and analyzed for

pesticides, semivolatile organic compounds (SVOCs), and

volatile organic compounds (VOCs). The results indicate

that many pesticides and other organic compounds are reaching the water resources of the basin and that some compounds have accumulated in fish tissue and bed sediment.

Although most of the compounds detected were at low concentrations, some compounds were detected at concentrations in excess of drinking-water standards or national

guidelines for the protection of fish-eating wildlife.

drains near Twin Falls contained concentrations of t

ticides chlorpyrifos and methylazinphos that exceed

USEPA criteria for the protection of aquatic life (see 

mary of Compound Detections and Concentrations, 

26). However, none of the stream samples collected 

1994 and 1995 contained concentrations of pesticide

exceeded USEPA drinking-water standards.

Rock Creek near Twin Falls has long been recogn

one of the most severely degraded streams in the Sta

Idaho [21]. During 2 years of monitoring at Rock Cr

different pesticides were detected in stream samples

of 43 samples contained at least 1 pesticide, most of 

were herbicides [22]. The number of pesticides and t

cide concentrations were largest in Rock Creek in th

and early summer following early season crop appli

[4]. This pattern is typical in many parts of the Unite

[19].

Similar to basinwide sampling results, the most c

monly detected compounds in Rock Creek were EPT

zine, desethylatrazine, metolachlor, and alachlor. C

Crop yields have improved in the upper Snake River Basin as a

result of widespread pesticide applications. Although many of the

pesticides currently in use break down rapidly in the environment following application, some pesticides are reaching the ground- and

surface-water supplies of the basin (photograph by M.G. Rupert,

U.S. Geological Survey).

Tributaries, such as Rock Creek near Twin Falls, discharge 

wastewater and associated pesticides to the Snake River. T

ber and concentrations of pesticides in water, bed sediment

tissue are largest in the downstream parts of the upper Sna

Basin (photograph by G.M. Clark, U.S. Geological Survey).

In basinwide stream sampling conducted in May and June

1994, EPTC, or Eptam (used on potatoes, beans, and sugar

beets); atrazine (used on corn) and its breakdown product

desethylatrazine; metolachlor (used on potatoes and beans);

and alachlor (used on beans and corn) were the most commonly detected pesticides, accounting for about 75 percent

of all detections [20]. Only four different pesticides were

detected in samples collected upstream from American Falls

Reservoir. No pesticides were detected in the Snake River or

its tributaries upstream from its confluence with the 

Fork. Seventeen different pesticides were detected d

stream from American Falls Reservoir; the largest nu

was detected in agriculturally degraded tributaries to 

Snake River between Twin Falls and Hagerman [20]

followup sampling in 1995, two samples from agricu
U.S. Geological Survey Circula

MAJOR ISSUES AND FIN

trations of the pesticides in Rock Creek were well below

USEPA drinking-water standards and aquatic-life criteria

[22]. Even though most of the pesticides in Rock Creek were

detected only during the growing season, atrazine and desethylatrazine, because of their mobility and relative resistance to breakdown, were detected year round at concentrations ranging from 0.01 to 0.03 microgram per liter.

Streambed sediment and bottom-feeding fish, primarily

suckers and carp, were collected and analyzed for organochlorine compounds such as DDT and PCBs. Because

most of these compounds are not water soluble and are not

readily broken down, many can remain in relatively large

concentrations in bed sediment and in the fat tissue of fish

for long periods of time. Although many of the organochlorine compounds have been banned from use in the United

States since the early 1970’s, studies conducted in the late

1980’s documented the presence of DDT in 98 percent of

fish-tissue samples collected at 388 stream sites across the

Nation [23]. However, comparison of fish-tissue data collected during the NAWQA study with data collected during

the early 1970’s indicates that the bans on use have been

effective in reducing the environmental concentratio

organochlorine compounds in the Snake River Basi

ples of tissue from fish collected from the Snake Ri

Twin Falls indicate that concentrations of DDT and 

organochlorine compounds, although still present, h

decreased substantially, some by as much as 10 tim

In the 1980’s, studies

determined that large

concentrations of the

organochlorine compounds DDT and PCBs in

fish tissue were resulting

in eggshell thinning and

poor reproductive success for fish predators

such as the bald eagle.

Today, bald eagle populations throughout the

United States are nearing recovery levels, which

will allow them to be

removed from the Endangered Species List (photograph © 1974 by W.H.

Mullins and published

with permission).

DDE, a breakdown product of DDT, was present in fish tissu

20 sites, or 80 percent of sites where samples were collect

the NAWQA study. PCBs were present in samples from 12 

sites. Overall, fish-tissue samples contained more organoc

compounds than did bed-sediment samples.

Total PCB

Toxaphene

alpha-HCH

Dieldrin

p, p'-DDT

o, p'-DDT

p, p'-DDE

o, p'-DDE

p, p'-DDD

o, p'-DDD

trans-Nonachlor

cis-Nonachlor

trans-Chlordane

cis-Chlordane

PERCENT DETECTION

0 25 75 50

Bed sedimen

Fish tissue
16 Water Quality in the Upper Snake River Basin, Idaho and Wyoming, 1992–95

MAJOR ISSUES AND FINDINGS

Of the 41 fish-tissue and 43 bed-sediment samples collected at 22 sites during the upper Snake River Basin

NAWQA, 14 different organochlorine compounds were

detected in fish tissue, and 9 organochlorine compounds and

47 SVOCs were detected in bed sediment [10]. The most frequently detected organochlorine compounds were DDT and

its breakdown products, DDD and DDE, present in fish tissue at 83 percent of the sites and in bed sediment at 

cent of the sites. At least one SVOC was detected in a

bed-sediment samples. The most frequently detected 

in bed sediment were phthalates (98 percent of the sa

phenol (86 percent), and 2,6-dimethylnaphthalene (8

cent). Sources of these compounds can be industrial 

reational activities. Currently, however, no human he

The positive results of the 1972 ban on the production and 

of DDT are evident in tissue concentrations in bottom-feed

Snake River near Twin Falls. Data were collected for the U

Wildlife Service National Contaminant Biomonitoring Prog

84) and the upper Snake River Basin NAWQA study (1992

Although concentrations of DDT have declined substantial

early 1970’s, because of their persistence, DDT and its bre

products are still present in fish tissue and bed sediment.

During 2 years of sampling at Rock Creek near

Twin Falls, the largest number and largest concentrations of pesticides were detected in the spring

and early summer following early season applications. This temporal pattern of pesticide detections

in surface water is typical across the Nation. Fortytwo of the 43 samples collected during the 2-year

period contained at least 1 pesticide.

Bottom-feeding fish, like this sucker, are sent to the U.S. Geological

Survey’s National Water Quality Laboratory, where their tissue is

analyzed for organochlorine compounds. Many organochlorine compounds, a number of which have been banned from use, accumulate in fish tissue, where they can be passed on to fish-eating

predators (photograph by T.R. Maret, U.S. Geological Survey).

10

8

6

4

2

0

NUMBER OF PESTICIDES DETECTED

A

1993

MJ A N J SO D A J J F AMJ M MJ A N SO D J F M

1994 1995

5

4

3

2

1

0

MICROGRAMS PER GRAM, WET WEIGHT

1966

1975

1985

1990

WATER YEAR

DDT banned

1970

1980

Criterion established by the National

Academy of Sciences and National

Academy of Engineering [24] for

the protection of predatory fish and wildlife
U.S. Geological Survey Circula

MAJOR ISSUES AND FIN

advisories for fish consumption are in force for streams in

the upper Snake River Basin.

In headwater streams where degradation of stream-water

quality is minimal, tissue of fish, primarily suckers, from

four of eight sites contained small concentrations of DDT

and its breakdown products. Although no obvious sources

exist for DDT in headwater areas of the upper Snake River

Basin, other studies in the Nation also have documented the

presence of DDT in fish tissue and bed sediments in pristine

watersheds [25]. Streams draining areas influenced by agricultural and industrial activities contained the largest number of organochlorine compounds and SVOCs and in the

largest concentrations [10]. Concentrations of organochlorine compounds in tissue of fish from the Portneuf River at

Pocatello, Rock Creek near Twin Falls, and Snake River

near Twin Falls equaled or exceeded national (NAS/NAE)

guidelines for the protection of fish-eating wildlife [10].

Water samples from domestic, irrigation, stock, and public supply wells were collected and analyzed for pesticides

and VOCs during a basinwide study conducted during the

summers of 1994 and 1995 [26]. Results showed that water

from 39 percent of 195 wells sampled contained at least 1

detectable pesticide (M.G. Rupert, U.S. Geological Survey,

written communication, 1997). Water from 13 percent of

the wells contained 3 or more pesticides. Fourteen different

pesticides and 11 different VOCs were detected in the 195

well samples. Atrazine (in 27 percent of the samples), desethyl-atrazine (in 27 percent), metribuzin (in 7 percent),

simazine (in 7 percent), and prometon (in 7 percent) were

the most commonly detected pesticides. None of these pesticides, however, exceeded USEPA drinking-water standards.

Results from the basinwide sampling, in conjunction

with intensive sampling in selected areas of the upper Snake

River Basin, showed no detectable pesticides in ground

water in some areas; however, in other areas, ground water

contained numerous pesticides. Samples collected from

wells in the Jackson, Wyoming, area; in the mountainous

northern part of the basin; and along the southern boundary

of the basin contained few, if any, pesticides. The largest

number and concentrations of pesticides were in samples

from wells that also contained large nitrate concentrations

and were located in agricultural areas adjacent to the Snake

River. Intensive sampling of 105 domestic and irrigation

wells in agricultural areas north of the Snake River between

Burley and Hagerman showed that water from 73 percent of

the wells contained at least 1 pesticide and that 41 percent

contained 3 or more pesticides (M.G. Rupert, U.S. Geological Survey, written communication, 1997). The VOC 1,2-

dichloropropane was the only organic compound detected

in ground water that exceeded USEPA drinking-water standards. However, it was detected in water from only one

shallow domestic well at a concentration of 6.6 micrograms

per liter [26].

Because the toxicological effects of drinking wate

contains multiple pesticides or other organic compo

not well understood [19], health risks associated wit

ing ground water in some areas of the basin cannot b

mined. More research is necessary to establish the h

risks associated with drinking water containing sma

centrations of more than one pesticide or other organ

pound.

Basinwide, EPTC, atrazine, and the atrazine breakdown pro

desethylatrazine were the most commonly detected pesticid

surface water. In ground water, atrazine, desethylatrazine, a

metribuzin were the most commonly detected pesticides. Th

percentage of detections of atrazine and desethylatrazine is 

prising because atrazine is not widely used on crops in the 

Snake River Basin.

Atrazine

100

80

60

40

20

0

PERCENTAGE OF SAMPLES WITH DETECTIONS

SURFACE WATER

EPTC

Metolachlor

Atrazine

Desethylatrazine

Alachlor

Ethopr

2,4-D

Diazinon

50

40

30

20

10

0

GROUND WATER

EPTC

Simazine

Metribuzin

Desethylatrazine

Prometon

Metolachl

p,p'-DDE

Based on samples collected at 37

sites basinwide, May-June 1994

Based on samples collected at 19

wells basinwide, 1994–1995
18 Water Quality in the Upper Snake River Basin, Idaho and Wyoming, 1992–95

MAJOR ISSUES AND FINDINGS

WHAT ARE THE WATER-QUALITY CONCERNS IN

THE SNAKE RIVER BETWEEN MILNER DAM AND

KING HILL? WHAT ARE THE PRIMARY SOURCES

OF POLLUTANTS?

Water quality in the 92-mile reach of the Snake River

between Milner Dam and King Hill at the upper Snake River

Basin outlet (see location map on page 4) is degraded

because of the cumulative effects of decades of agricultural

and industrial activities. Sources of pollutants to the Snake

River downstream from Milner Dam include irrigation

returns, agriculturally degraded tributary streams, fish farms,

and wastewater-treatment facilities [4]. Since 1990, the reach

from Milner Dam to King Hill has been listed by the Idaho

Division of Environmental Quality as “water-quality limited” under the Federal Clean Water Act. The listing indicates degraded water-quality conditions and a violation of at

least one State water-quality criterion. Excessive aquatic

vegetation, low dissolved oxygen, and high water temperatures in the reach are violations. Because of the degraded

conditions, beneficial uses of the reach for aquatic life, fishing, swimming, and boating are impaired [27].

Numerous factors contribute to the poor water-quality

conditions in the Snake River from Milner Dam to King Hill.

These factors include input of excessive nutrients, pesticides,

and sediment from a variety of sources, and alterations in

streamflow conditions [4,27]. An abundance of nutrients

such as nitrogen and phosphorus, associated with sufficient

bed sediment, provides aquatic plants with the ideal environment for rapid growth. Overabundance of aquatic plants, or

eutrophication, is the process creating the degraded waterquality conditions in the Snake River from Milner Dam to

King Hill. A water body that has become eutrophic has a

wide fluctuation in dissolved-oxygen concentrations and

does not support a healthy biological community. When

aquatic plants die, they settle to the stream bottom and

decompose, causing further dissolved-oxygen deple

odor problems, and a source of nutrients for more aq

plant growth. Historically, large streamflows during 

snowmelt have scoured bed sediment and transporte

downstream. However, drought conditions in recent 

upstream diversions, and impoundments in the reach 

substantially reduced streamflow and streamflow ve

in the Snake River downstream from Milner Dam [2

ing most years, the main source of water to the Snak

downstream from Milner Dam is numerous springs 

charge ground water to the river [17]. However, beca

amount of water supplied by the springs is not suffic

scour bed sediment and decaying plants, these mater

accumulate on the river bottom, where they supply s

for aquatic plants and act as a storage reservoir for n

[27].

The biological community in the Snake River bet

Milner Dam and King Hill has become severely stres

result of the eutrophic conditions [6]. Large dissolve

gen and temperature fluctuations have resulted in wa

ity conditions that are intolerable for many aquatic

The Snake River between Milner Dam and King Hill receives w

pollutants from a variety of nonpoint and point sources. A dram

trast in water quality is visually apparent (see arrow) where sed

ground water discharges to the river (photograph © 1978 by W

and published with permission).

Accumulations of soft, finegrained sediment in the

river bottom, along with an

abundant supply of nutrients, result in algae blooms

and dense growths of

aquatic plants such as

these in the Snake River

near Twin Falls (photograph

by G.M. Clark, U.S. Geological Survey).

The percentage of the annual contribution of water to the Snake R

springs along the north bank of the Snake River between Milner D

King Hill varies depending on water conditions in the upper Snake 

Basin. During the wet years from 1982 to 1986, the springs provid

50 percent of the water annually leaving the basin at King Hill. Du

years from 1988 to 1992, the springs provided more than 68 perc

water annually leaving the basin.

Eight species of endangered snails, such as this

Banbury Springs limpet,

inhabit areas of the Snake

River between Milner Dam

and King Hill. A number of

studies are underway to

determine the extent and

abundance of these snail

populations in the basin

(photograph © 1994 by

W.H. Mullins and published with permission).

20,000

18,000

16,000

14,000

12,000

10,000

8,000

6,000

4,000

2,000

0

Mean annual streamflo

 River at King Hill

Mean annual discharge

 springs

Percentage of annual st

 at King Hill contribu

 north-side springs

CUBIC FEET PER SECOND

1980

WATER YEAR

1983 1989 1986 1992

42

64 68 48 36 33 42 40 57 79 74 69 69 71 
U.S. Geological Survey Circula

MAJOR ISSUES AND FIN

organisms. In addition, many of the deep pools and gravel

beds once common in the reach have been filled with sediment and decaying plant material and no longer provide suitable habitat for many native species. Few trout or other

native fish species currently survive in the reach, which is

now dominated by species adapted to polluted, warmwater

conditions [6,7]. Downstream dams on the Snake and

Columbia Rivers have blocked access to the Snake River

between Shoshone Falls and King Hill for other species such

as chinook salmon, steelhead, Pacific lamprey, and white

sturgeon. Of these species, only the white sturgeon survives

in the reach. Seven species of snails and two other species of

fish currently inhabiting areas in the reach either have been

federally listed or are being considered for listing as endangered or threatened. As a result of the listings, the U.S. Fish

and Wildlife Service has issued a recovery plan for the

endangered and threatened species in the reach [28].

Sources of pollutants to the Snake River downstream from

Milner Dam include irrigation return flows, agriculturally

affected tributary streams, fish farms, and wastewater-treatment facilities [4]. Sources such as agriculture, food processing and other industries, and confined-animal feeding

operations may not discharge directly to the Snake River;

rather, pollutants from these sources are, in many instances,

transported to the ground water and ultimately discharged to

the Snake River. On the basis of data collected during the

NAWQA study and by other agencies, contributions of nitrogen, phosphorus, and sediment to the Snake River between

Milner Dam and King Hill were estimated for 1995 [4]. The

estimates indicate that ground water discharging as 

supplied about 60 percent of the 14,000 tons of total 

that entered the reach during 1995. Tributary stream

fish farms contributed 18 and 12 percent of the total n

respectively. Fish farms, tributary streams, and the T

Falls wastewater-treatment facility contributed 34, 1

13 percent, respectively, of the 840 tons of total pho

entering the reach in 1995. Sources upstream from M

Dam contributed 21 percent of the total phosphorus. 

120,000 tons of sediment entered the reach in 1995. 

agriculturally affected tributaries—Rock Creek, Ced

Mud Creek, Deep Creek, Salmon Falls Creek, and th

River—contributed about 58 percent of the sediment 

the reach, and upstream sources and irrigation return 

contributed 24 and 14 percent, respectively.

The degraded conditions in the Snake River betw

ner Dam and King Hill and increasing water-resourc

demands by user groups have raised public awarene

this reach of the river. Restoring and maintaining the 

quality of the Snake River and protecting existing us

recognized as important factors influencing the futur

nomic and social well-being of the region. Simply re

nutrient and sediment inputs to the river might not b

cient to reverse the eutrophication process occurring 

Snake River downstream from Milner Dam. Future 

ment strategies also might need to ensure that stream

the reach are sufficient to move nutrients and sedime

downstream and to prevent future accumulations.

Fish farms along the Snake

River use sediment-free

spring discharge to raise

fish for stocking and commercial use. More than 200

hatcheries in the reach

between Milner Dam and

King Hill account for more

than 70 percent of the liveweight of trout commercially produced in the

Nation (photograph © 1995

by W.H. Mullins and published with permission).

electric power production, drinking water for local residents, and habitat

for native species of fish and endangered snails. In recent years, the

amount of water discharging from the springs has declined as a result of

increased ground-water withdrawals, more efficient irrigation practices

which result in less recharge to the aquifer, and drought conditions (photograph © 1995 by W.H. Mullins and published with permission).

Along the north bank

of the Snake River

between Milner Dam

and King Hill are 11 of

the 65 springs in the

United States that

discharge more than

100 cubic feet per

second. In addition to

the use of spring

water in fish hatcheries, the springs also

are used for hydro- In 1995, springs provided 60 percent of the approximately 14,0

nitrogen that entered the Snake River between Milner Dam an

Fish farms and Snake River water coming through Milner Dam 

sources) were the primary contributors of phosphorus in 1995

ally affected tributaries to the Snake River provided about 58 p

the 120,000 tons of sediment entering the Snake River betwee

Dam and King Hill.

Upstream so

Springs

Tributary str

Irrigation dr

Fish farms

Municipal w

 treatment 

EXPLANAT

Total nitrogen

14,000 tons

Sediment

120,000 tons

Total phospho

840 tons

60% 18%

12%

7%

2%

1%

2

34%

4%

16%

12%

58%

24%

14%

4%

1%
20 Water Quality in the Upper Snake River Basin, Idaho and Wyoming, 1992–95

WATER-QUALITY CONDITIONS IN A NATIONAL CONTEXT

EXPLANATION

Ranking of stream quality relative

to all NAWQA stream sites—Darker

colored circles generally indicate poorer

quality. Bold outline of circle indicates

that one or more aquatic-life criteria

were exceeded.

Greater than the 75th percentile

 (Among the highest 25 percent of NAWQA

 stream sites)

Between the median and the 75th

 percentile

Between the 25th percentile and

 the median

Less than the 25th percentile

 (Among the lowest 25 percent of NAWQA

 stream sites)

Only two sites in the upper Snake

River Basin had sufficient pesticide

data to compare with national conditions. Although numerous pesticides

were detected at these sites (Teton

River near St. Anthony and Rock

Creek near Twin Falls), the concentrations were among the smallest of

those reported in all NAWQA Study

Units. None of the concentrations

exceeded drinking-water standards

or aquatic-life criteria.

Comparison of Stream Quality in the Upper Snake River Basin With NAWQA Findings Nationwide

Seven major water-quality characteristics were evaluated for stream sites in ea

NAWQA Study Unit. Summary scores for each characteristic were computed for 

that had adequate data. Scores for each site in the upper Snake River Basin were 

pared with scores for all sites sampled in the 20 NAWQA Study Units during 199

Results are summarized by percentiles; higher percentile values generally indicat

quality compared with that at other NAWQA sites. Water-quality conditions at ea

also are compared with established criteria for protection of aquatic life. Applica

ria are limited to nutrients and pesticides in water, and semivolatile organic comp

organochlorine pesticides, and PCBs in sediment. (Methods used to compute ran

and evaluate aquatic-life criteria are described by Gilliom and others, in press [29

Idaho

Falls

Pocatello

Twin

Falls

Snake

River

NUTRIENTS

King

Hill

In general, nutrient c

tions in streams of th

Snake River Basin w

among the smallest o

reported in all NAW

Units. Concentration

ents in the Snake Riv

increased in a downs

direction; concentrat

largest between Twin Falls 

basin outlet at King Hill. S

stream from agricultural ar

tained the largest concentr

nutrients in the basin. How

of the concentrations exce

drinking-water standards f

ents.

Idaho

Falls

Pocatello

Twin

Falls

Snake

River

PESTICIDES

King

Hill

Idaho

Falls

Pocatello

Twin

Falls

Snake

River

PCBs AND OTHER ORGANOCHLORIN

in sediment and fish tissue

King

Hill

concentrations reported in other NAWQA Study Units; concentrations at abou

of the sites were larger and about half were smaller, compared with the nation

median determined by NAWQA. Concentrations in fish tissue at two sites exc

NAS/NAE aquatic-life criteria. These sites were Rock Creek at Twin Falls an

Snake River near Twin Falls. Compounds that exceeded aquatic-life criteria w

PCBs, the insecticide DDT, and the DDT breakdown products DDE and DDD 

Concentrations were largest at sites downstream from agricultural and urban a

Concentrations of PCBs

and other organochlorines

in bed sediment and fish

tissue in the upper Snake

River Basin were typical of
U.S. Geological Survey Circula

WATER-QUALITY CONDITIONS IN A NATIONAL CO

Idaho

Falls

Pocatello

Twin

Falls

Snake

River

STREAM HABITAT

King

Hill

Trace-element contamination does not appear to be a

concern in most areas of the upper Snake River Basin.

Concentrations in bed sediment were largest in pristine

areas where the geology is naturally rich in trace elements.

Basin, 47 different SVOCs were detected in bed-sediment sample

commonly detected SVOCs were phthalates (98 percent of the sa

phenol (86 percent of the samples), and 2,6-dimethylnaphthalene 

of the samples). Concentrations of SVOCs in bed sediment were 

sites upstream from the influence of municipal and (or) industrial 

sediment samples at Snake River sites downstream from Idaho F

tained SVOC concentrations that ranked higher than the national 

determined by NAWQA. However, no concentrations of SVOCs 

ment exceeded NAS/NAE aquatic-life criteria.

Fish community indices, such as the number of omnivores, 

tolerant species, and non-native fish, indicated that most of 

assessed in the upper Snake River Basin were more degrade

were sites sampled in other NAWQA Study Units. Fish com

were most degraded in the Snake River and its tributaries dow

from Twin Falls, where multiple sources of pollutants degra

quality conditions. Even sites where degradation was minim

showed some degradation as a result of introduced fish spec

In general, nutrient and pesticide concentrations in streams in the upper Snake River Basin were small compared with 

trations in other streams sampled by NAWQA nationwide. Concentrations of nutrients and pesticides did not exceed drin

water standards in any of the stream samples collected.

PCBs and other organochlorine compounds are more of a concern in fish tissue than in bed sediment. Concentrations 

compounds exceeded aquatic-life criteria for fish tissue at two sites. PCBs and the insecticide DDT and its breakdown pr

were the most commonly detected organochlorine compounds in bed sediment and fish tissue.

Fish communities in large rivers downstream from anthropogenic effects were degraded compared with communities 

sampled in other NAWQA Study Units. Degraded sites supported primarily nongame, warmwater species of fish. Headw

streams and large rivers upstream from anthropogenic effects supported healthy communities of predominantly coldwate

quality and associated biological communities of streams.

Instream modification, bank erosion, and riparian conditions

represent useful measures of stream habitat conditions. In the

upper Snake River Basin, the habitat conditions were generally better than those at other NAWQA sites nationwide.

Sites where habitat was highly degraded were influenced primarily by hydrologic modification and agricultural activities

such as excessive grazing. Because bank and riparian conditions generally are not reflective of habitat conditions in large

rivers, the large-river sites in the upper Snake River Basin

were not evaluated for stream habitat conditions.

Stream habitat conditions can

strongly influence the water

Semivolatile

organic compounds typically are

present in streams

receiving municipal

and (or) industrial

discharges. In the

upper Snake River

CONCLUSIONS

Idaho

Falls

Pocatello

Twin

Falls

Snake

River

TRACE ELEMENTS

in sediment

King

Hill

Idaho

Falls

Pocatello

Twin

Falls

Snake

River

FISH COMMUNITIES

King

Hill

Idaho

Falls

Pocatello

Twin

Falls

Snake

River

SEMIVOLATILE ORGANIC

COMPOUNDS (SVOCs)

in sediment

King

Hill
22 Water Quality in the Upper Snake River Basin, Idaho and Wyoming, 1992–95

WATER-QUALITY CONDITIONS IN A NATIONAL CONTEXT

Five major water-quality characteristics were evaluate

ground-water studies in each NAWQA Study Unit. Groun

resources were divided into two categories: (1) drinking-

aquifers and (2) shallow ground water underlying agricu

urban areas. Summary scores were computed for each ch

istic for all aquifers and shallow ground-water areas that 

quate data. Scores for each aquifer and shallow ground-w

area in the upper Snake River Basin were compared with 

for all aquifers and shallow ground-water areas sampled 

NAWQA Study Units during 1992–95. Results were sum

by percentiles; higher percentile values generally indicat

quality compared with other NAWQA ground-water stud

Water-quality conditions for each drinking-water aquifer 

were compared with established drinking-water standard

criteria for protection of human health. (Methods used to 

pute rankings and evaluate standards and criteria are desc

Gilliom and others, in press [29].)

Radon concentrations in water from wells in the tributary valley, Jackson Valley, and Minidoka study areas

were larger than the national median determined by NAWQA. Concentrations in water from nearly all wells

sampled in these three study areas exceeded the USEPA proposed drinking-water standard of 300 picocuries

per liter. Radon concentrations were smaller than the national median in the eastern Snake River Plain, A&B,

Jerome/Gooding, and Eden study areas. Radon is naturally occurring and is produced by the radioactive

decay of uranium-containing minerals in local geologic materials.

Nitrate is one of the most common anthropogenic-induced 

nants in ground water in the upper Snake River Basin. Nitra

trations in ground water from the Minidoka study area were 

the largest of those reported in all NAWQA Study Units; co

tions in water from 24 percent of the wells sampled exceed

drinking-water standard of 10 milligrams per liter. Nitrate c

tions also were larger than the national median in the easter

River Plain, A&B, and Eden study areas.

Comparison of Ground-Water Quality in the Upper Snake River Basin With NAWQA Findings Nation

Idaho

Falls

Pocatello

Twin

Falls

NITRATE

King

Hill

Idaho

Falls

Pocatello

Twin

Falls

RADON

King

Hill

EXPLANATION

Eastern Snake River Plain study area

Tributary valley study area

Jackson Valley study area

Minidoka study area

A&B study area

Jerome/Gooding study area

Eden study area

Ranking of ground-water quality relative to

all NAWQA ground-water studies—Darker

colored circles generally indicate poorer quality.

Bold outline of circle indicates that one or more

standards or criteria were exceeded.

Greater than the 75th percentile

 (Among the highest 25 percent of NAWQA

 ground-water studies)

Between the median and the 75th

 percentile

Between the 25th percentile and

 the median

Less than the 25th percentile

 (Among the lowest 25 percent of NAWQA

 ground-water studies)
U.S. Geological Survey Circula

WATER-QUALITY CONDITIONS IN A NATIONAL CO

CONCLUSIONS

In general, ground water in the upper Snake River 

safe to drink; the quality of ground water in the Jackso

area is some of the highest quality ground water repo

the NAWQA Study Units. However, ground-water qu

some areas of the basin has been degraded as a result 

anthropogenic activities. Nitrate poses the greatest con

public health. Nitrate concentrations in ground water 

areas of the upper Snake River Basin were near or ex

the USEPA drinking-water standard of 10 milligrams 

Nitrate and DS concentrations in ground water in the 

doka, A&B, and Eden study areas were some of the l

those reported in all NAWQA Study Units.

Pesticide occurrence in ground water also poses so

cern. Even though pesticide concentrations did not ex

USEPA drinking-water standards, the numbers of pes

detected in some areas were large. More research is n

establish the toxicological effects of drinking water th

tains small concentrations of more than one pesticide 

organic compound.

Water from wells in the Minidoka, A&B, and Eden

study areas contained some of the largest DS concentrations of those reported in all NAWQA Study

Units. Large DS concentrations probably result

from leaching of evaporative salts and soil minerals

during infiltration of irrigation water.

Volatile organic compounds include solvents, fuels, and soil fumiga

Eleven different VOCs were detected in ground water in the upper S

River Basin. Only 1,2-dichloropropane exceeded USEPA drinking-w

dards, and in water from only one well in the Minidoka study area. 

from only one well in the Jackson Valley contained VOCs; the sour

bly was a local landfill.

Pesticide detections in water from wells in the Jackson Valley study

area were among the smallest of those reported in all NAWQA

Study Units. Pesticide detections in water from wells in the Minidoka, A&B, and Eden study areas were larger than the national

median determined by NAWQA; water from 86 percent of the

wells sampled in the Minidoka study area contained at least one

detectable pesticide. None of the concentrations in ground water in

the upper Snake River Basin exceeded USEPA drinking-water standards.

Idaho

Falls

Pocatello

Twin

Falls

PESTICIDES

King

Hill

Idaho

Falls

Pocatello

Twin

Falls

VOLATILE ORGANIC COMPOUNDS 

King

Hill

Idaho

Falls

Pocatello

Twin

Falls

DISSOLVED SOLIDS (DS)

King

Hill
24 Water Quality in the Upper Snake River Basin, Idaho and Wyoming, 1992–95

STUDY DESIGN AND DATA COLLECTION

The primary objectives of the

stream chemistry component of

study were to assess the relation

between land use and chemical

constituents in surface water and to

evaluate fluxes of contaminants in

the Snake River. Synoptic studies

were designed to assess sources

and fluxes of contaminants during

selected hydrologic conditions.

Intensive sites were monitored for

pesticides during a 2-year period

from 1993 to 1995.

The primary objectives of the ground-water

chemistry component of study were to assess the

regional water chemistry of the Study Unit and

to determine whether the chemical constituents

in ground water were related to specific land

uses. Samples for regional studies were collected

from irrigation, stock, domestic, and public supply wells. Samples for land-use studies were collected mostly from domestic wells completed in

a single aquifer.

Basic site

Basic and intensive

 site

Synoptic site

Special studies

Rangeland

Forest land

Agricultural

 land

Other

Stream Chemistry

EXPLANATION

0

0

20

20

40 MILES

115° 40 KILOMETERS

42°

43°

115°

114°

44°

113°

112° 111°

110°

44°

110°

43°

111°

112°

113°

114°

42°

Twin

Falls

Pocatello

Idaho

Falls

American

Falls

Reservoir

Snake River

Snake

River Jackson Henrys

Lake

Fork

IDAHO

NEVADA UTAH

WYOMING

IDAHO

King

Hill

The primary objective of the stream ecology

component of study was to assess the surfacewater quality by integrating the chemical, physical, and biological factors. Stream ecology

sites were distributed among major ecoregions

and dominant land uses, which included irrigated agriculture, forested land, and rangeland.

The stream types sampled represented wadable

streams, large rivers, and least-disturbed springs

and streams. Sites were classified as intensive or

synoptic on the basis of the level of the sampling effort or the number of years data were

collected.

Ground-Water Chemistry

EXPLANATION

0

0

20

20

40 MILES

115° 40 KILOMETERS

42°

43°

115°

114°

44°

113°

112° 111°

110°

44°

110°

43°

111°

112°

113°

114°

42°

King

Hill

Twin

Falls

Pocatello

Idaho

Falls

American

Falls

Reservoir

Snake River

Snake

River Jackson Henrys

Lake

Fork

IDAHO

NEVADA UTAH

WYOMING

IDAHO

Well

Eastern Snake

 River Plain

Tributary valleys

STUDY AREAS

Jackson Valley

Minidoka

A&B

Jerome/Gooding

Eden

Stream Ecology

Intensive assessments of

 biology and contaminants

Synoptic assessments of

 least-disturbed reference

 sites with contaminants

Synoptic assessments of

 least-disturbed reference

 sites without contaminants

Synoptic assessments of

 contaminants only

Special study of least-

 disturbed springs

0

0

20

20

40 MILES

115° 40 KILOMETERS

42°

43°

115°

114°

44°

113°

112° 111°

111°

112°

113°

114°

42°

Twin

Falls

Pocatello

Idaho

Falls

American

Falls

Reservoir

Snake River

Snake

River J

Henrys

Fork

IDAHO

NEVADA UTAH

WYOMING

IDAHO Nort

Midd

Snak

 Hi

Wyo

Nort

 Ra

Mon

 Fo

EXPLANATION

ECOREG

King

Hill

Ecoregions m

Omernik and 
U.S. Geological Survey Circula

STUDY DESIGN AND DATA COLLE

SUMMARY OF DATA COLLECTION IN THE UPPER SNAKE RIVER BASIN STUDY UNIT, 1992–95

Study

component What data were collected and why Types of sites sampled Numberof sites

Sampling fr

and pe

Stream chemistry

Basic sites—

general water

chemistry

Streamflow, nutrients, major ions, organic carbon, suspended

sediment, water temperature, specific conductance, pH, and

dissolved oxygen to describe concentrations and seasonal variations. Stable isotopes and tritium sampled quarterly.

Streams draining basins representative of common land-use types.

Also large-river sites that integrate multiple types of land use.

12 Monthly plus 

high streamflo

Apr. 1993–A

Intensive sites—

pesticides

In addition to the above constituents, dissolved concentrations

of 87 pesticides to describe seasonal variations.

Subset of basic sites draining areas

of predominantly agricultural

land use.

2 Weekly to 

Apr. 1993–A

Synoptic

sites—water

chemistry

Streamflow, nutrients, dissolved concentrations of 87 pesticides,

suspended sediment, selected isotopes, water temperature, specific conductance, pH, and dissolved oxygen to describe concentrations, assess spatial variability, and determine chemical

and sediment fluxes.

Additional main-stem sites, varied land-use sites, and sites in the

Rock Creek watershed. Snake

River sites between Milner Dam

and King Hill.

19

13

May and Ju

August 

Stream ecology

Intensive

assessments

Fish, macroinvertebrates, algae, instream and riparian habitat to

assess aquatic biological community structure. Continuous

summer water temperature and field parameters collected.

Contaminants in bed sediments: Total PCBs, 32 organochlorine

pesticides, 78 semivolatile organic compounds, and 44 trace

elements to determine occurrence and spatial distribution.

Contaminants in bottom-feeding aquatic biota: Total PCBs, 30

organochlorine pesticides, and 24 trace elements to determine

occurrence and spatial distribution. Organic contaminants in

whole fish. Trace elements in fish livers and caddisflies.

Organic contaminants and trace elements in fillets of gamefish

(one basic site).

All basic sites.

All basic sites.

All basic sites.

12

12

12

Once in 

6 sites multi

(1993–

2 sites multi

6 sites multi

1 site multip

6 sites multi

1 site multip

Synoptic studies Similar to the intensive assessment sites, except only one reach

per site sampled to assess spatial distribution and reference

conditions of aquatic communities and associated habitats.

Contaminants in bottom-feeding aquatic biota and in bed sediments.

 Least-disturbed reference sites.

Some least-disturbed reference

sites, some spring sites, and some

basic sites.

12

10

Once in 

Onc

(mostly in 1

Ground-water chemistry

Regional Study

Unit surveys

 Major ions, nutrients, 87 pesticides, volatile organic compounds, and radon to assess occurrence. Data collected in

cooperation with the Idaho Statewide Ground-Water Monitoring Program.

Domestic, irrigation, stock, and

public supply wells from a wide

range of well depths.

Snake River Plain, Idaho.

Tributary valleys, Idaho.

Jackson Valley, Wyoming.

43

39

20

Once in 

Once in 

Once in 

Local land-use

studies

Major ions, nutrients, 87 pesticides, 60 volatile organic compounds, radon, and selected isotopes to assess the effects of

land use and hydrogeology on ground-water quality in locally

important aquifers of the basin.

Mostly domestic wells.

A&B study area, mean well depth

230 feet.

Minidoka study area, mean well

depth 40 feet.

Jerome/Gooding study area, mean

well depth 240 feet.

Eden study area, mean well depth

380 feet.

31

29

30

15

Once in 

Once in 

Once in 

Once in 

Special studies

Springs between

Milner Dam and

King Hill: water

chemistry and

aquatic biota

assessment

Nutrients, pesticides, and selected isotopes to determine source

water of springs and nutrient loads from ground water to

the Snake River. Aquatic habitat and communities of fish,

macroinvertebrates, and algae in least-disturbed spring

environments.

Springs representing the entire

reach from Milner Dam to King

Hill.

Least-disturbed springs for biological assessment, subset of above

springs.

10

6

Springs samp

1994, Oct. 1

Aug. 1

Ecology samp

Apr. 1
26 Water Quality in the Upper Snake River Basin, Idaho and Wyoming, 1992–95

SUMMARY OF COMPOUND DETECTIONS AND CONCENTRATIONS

Herbicide

(Trade or common

name)

Rate

of

detection b

Concentration, in μg/L

0.001 0.01 0.1 1 10 100 1,000

The following tables summarize data collected for NAWQA studies during 1992–95 by showing results for the Upp

River Basin Study Unit compared with the NAWQA national range for each compound detected. The data were collected a

ety of places and times. In order to represent the wide concentration ranges observed among Study Units, logarithmic scale

emphasize the general magnitude of concentrations (such as 10, 100, or 1,000), rather than the precise number. The compl

used to construct these tables is available upon request.

Concentrations of herbicides, insecticides, volatile organic compounds, and nutrients detected in ground and surface water 

Snake River Basin Study Unit. [mg/L, milligrams per liter; μg/L, micrograms per liter; pCi/L, picocuries per liter; %, percent; 

- -, not measured; trade names may vary]

EXPLANATION

Range of surface-water detections in all 20 Study Units

Detection in the Upper Snake River Basin Study Unit

Range of ground-water detections in all 20 Study Units

Drinking-water standard or guideline a

Freshwater-chronic criterion for the protection of aquatic life a

Herbicide

(Trade or common

name)

Rate

of

detection b

Concentration, in μg/L

0.001 0.01 0.1 1 

Propachlor (Ramrod,

propachlore)

<1%

<1%

Propanil (Stampede,

Surcopur)

0%

<1%

Simazine (Aquazine,

Princep, Gesatop)

1%

8%

Tebuthiuron (Spike,

Perflan)

1%

0%

Terbacilc (Sinbar) 0%

<1%

Triallate (Far-Go) <1%

0%

Trifluralin (Treflan,

Trinin, Elancolan)

2%

0%

Insecticide

(Trade or common

name)

Rate

of

detection b

Concentration, in μg/L

Aldicarb sulfoxidec

(Aldicarb metabolite)

0%

1%

Azinphos-methylc

(Guthion, Gusathion)

1%

0%

Carbarylc (Sevin,

Savit)

1%

<1%

Carbofuranc

(Furadan, Curaterr)

1%

<1%

Chlorpyrifos (Dursban, Lorsban)

2%

0%

p,p’-DDE (p,p’-DDT

metabolite)

<1%

<1%

0.001 0.01 0.1 1 

Alachlor (Lasso) 2%

<1%

Atrazine (AAtrex,

Gesaprim)

19%

21%

Desethylatrazinec

(Atrazine metabolite)

7%

14%

Bromacil (Hyvar X,

Urox B, Bromax)

0%

2%

2,4-D (2,4-PA) 14%

1%

DCPA (Dacthal,

chlorthal-dimethyl)

1%

0%

Dinoseb (DNBP, DN

289, Premerge, Aretit)

0%

<1%

Diuron (Karmex,

Direx, DCMU)

2%

1%

EPTC (Eptam) 33%

<1%

Ethalfluralin (Sonalan, Sonalen)

3%

0%

Metolachlor (Dual,

Pennant)

5%

<1%

Metribuzin (Lexone,

Sencor)

1%

4%

Molinate (Ordram) 0%

1%

Napropamide

(Devrinol)

1%

0%

Pendimethalin

(Prowl, Stomp)

<1%

0%

Prometon (Gesagram, prometone)

<1%

3%
U.S. Geological Survey C

SUMMARY OF COMPOUND DETECTIONS AND CONCE

Diazinon <1%

0%

Dieldrin (Panoram D31, Octalox)

1%

<1%

Ethoprop (Mocap,

Prophos)

<1%

0%

Fonofos (Dyfonate) <1%

0%

alpha-HCH (alphaBHC, alpha-lindane)

0%

<1%

Malathion (maldison,

malathon, Cythion)

1%

0%

Phorate (Thimet,

Rampart)

1%

0%

Volatile organic

compound

(Trade or common

name)

Rate

of

detection b

Concentration, in μg/L

1,1,1-Trichloroethane

(Methylchloroform)

0%

<1%

1,1-Dichloroethane

(Ethylidene dichloride)

0%

<1%

1,2-Dichloropropane

(Propylene dichloride)

0%

<1%

1,3-Dichloropropane 0%

<1%

Benzene 0%

<1%

Dichlorodifluoromethane

0%

<1%

total Trihalomethanes 0%

<1%

Trichloroethene

(TCE)

0%

<1%

Trichlorofluoromethane

0%

<1%

cis-1,2-Dichloroethene

0%

<1%

0.01 0.1 1 10 100 1,000

Tetrachloroethene

(Perchloroethene)

0%

<1%

Nutrient

(Trade or common

name)

Rate

of

detection b

Concentration, in mg/L

Dissolved ammonia 84%

63%

Dissolved ammonia

plus organic nitrogen

as nitrogen

28%

9%

Dissolved phosphorus as phosphorus

61%

70%

Dissolved nitrite plus

nitrate

87%

97%

Other Rate

of

detection b

Concentration, in pCi/L

Radon-222

94%

0.01 0.1 1 10 100 

1 10 100 1,000 

Volatile organic

compound

(Trade or common

name)

Rate

of

detection b

Concentration, in μg/L

0.01 0.1 1 10 100 

Insecticide

(Trade or common

name)

Rate

of

detection b

Concentration, in μg/L

0.001 0.01 0.1 1 10 100 1,000
28 Water Quality in the Upper Snake River Basin, Idaho and Wyoming, 1992–95

SUMMARY OF COMPOUND DETECTIONS AND CONCENTRATIONS

Herbicides, insecticides, volatile organic compounds, and nutrients not detected in ground and surface water of the Upper 

Basin Study Unit.

Herbicides

2,4,5-T

2,4,5-TP (Silvex, Fenoprop)

2,4-DB (Butyrac, Butoxone, Embutox Plus, Embutone)

2,6-Diethylaniline (Metabolite of Alachlor)

Acetochlor (Harness Plus,

Surpass)

Acifluorfen (Blazer, Tackle

2S)

Benfluralin (Balan, Benefin,

Bonalan, Benefex)

Bentazon (Basagran, Bentazone, Bendioxide)

Bromoxynil (Buctril, Brominal)

Butylate (Sutan +, Genate

Plus, Butilate)

Chloramben (Amiben,

Amilon-WP, Vegiben)

Clopyralid (Stinger, Lontrel, Reclaim, Transline)

Cyanazine (Bladex, Fortrol)

Dacthal mono-acid (Dacthal

metabolite)

Dicamba (Banvel, Dianat,

Scotts Proturf)

Dichlorprop (2,4-DP, Seritox 50, Kildip, Lentemul)

Fenuron (Fenulon, Fenidim)

Fluometuron (Flo-Met,

Cotoran, Cottonex, Meturon)

Linuron (Lorox, Linex, Sarclex, Linurex, Afalon)

MCPA (Rhomene, Rhonox,

Chiptox)

MCPB (Thistrol)

Neburon (Neburea, Neburyl, Noruben)

Norflurazon (Evital, Predict, Solicam, Zorial)

Oryzalin (Surflan, Dirimal)

Pebulate (Tillam, PEBC)

Picloram (Grazon, Tordon)

Pronamide (Kerb, Propyzamid)

Propham (Tuberite)

Thiobencarb (Bolero, Saturn, Benthiocarb, Abolish)

Triclopyr (Garlon, Grandstand, Redeem, Remedy)

Insecticides

3-Hydroxycarbofuran (Carbofuran metabolite)

Aldicarb sulfone (Standak,

aldoxycarb, aldicarb metabolite)

Aldicarb (Temik, Ambush,

Pounce)

Disulfoton (Disyston, DiSyston, Frumin AL,

Solvirex, Ethylthiodemeton)

Methiocarb (Slug-Geta,

Grandslam, Mesurol)

Methomyl (Lanox, Lannate, Acinate)

Methyl parathion (PenncapM, Folidol-M, Metacide,

Bladan M)

Oxamyl (Vydate L, Pratt)

Parathion (Roethyl-P, Alkron, Panthion, Phoskil)

Propargite (Comite, Omite,

Ornamite)

Propoxur (Baygon, Blattanex, Unden, Proprotox)

Terbufos (Contraven,

Counter, Pilarfox)

cis-Permethrin (Ambush,

Astro, Pounce, Pramex, Pertox, Ambushfog, Kafil, Perthrine, Picket, Picket G,

Dragnet, Talcord, Outflank,

Stockade, Eksmin, Coopex,

Peregin, Stomoxin, Stomoxin P, Qamlin, Corsair,

Tornade)

gamma-HCH (Lindane,

gamma-BHC, Gammexane,

Gexane, Soprocide, gammahexachlorocyclohexane,

gamma-benzene hexachloride)

Chlorobenzene

(Monochlorobenzene)

Chloroethane (Ethyl chloride)

Chloroethene (Vinyl chloride)

Chloromethane (Methyl

chloride)

Dibromomethane (Methylene dibromide)

Dichloromethane (Methylene chloride)

Dimethylbenzenes

(Xylenes (total))

Ethenylbenzene (Styrene)

Ethylbenzene (Phenylethane)

Hexachlorobutadiene

Isopropylbenzene

(Cumene)

Methyl tert-butyl etherd

(MTBE)

Methylbenzene (Toluene)

Naphthalene

Tetrachloromethane (Carbon tetrachloride)

cis-1,3-Dichloropropene

((Z)-1,3-Dichloropropene)

n-Butylbenzene (1-Phenylbutane)

n-Propylbenzene (Isocumene)

p-Isopropyltoluene (pCymene)

sec-Butylbenzene

tert-Butylbenzene

trans-1,2-Dichloroethene

((E)-1,2-Dichlorothene)

trans-1,3-Dichloropropene

((E)-1,3-Dichloropropene)

Nutrients

No non-dete

Volatile organic

compounds

1,1,1,2-Tetrachloroethane

(1,1,1,2-TeCA)

1,1,2,2-Tetrachloroethane

1,1,2-Trichloro-1,2,2-trifluoroethane (Freon 113,

CFC 113)

1,1,2-Trichloroethane

(Vinyl trichloride)

1,1-Dichloroethene

(Vinylidene chloride)

1,1-Dichloropropene

1,2,3-Trichlorobenzene

(1,2,3-TCB)

1,2,3-Trichloropropane

(Allyl trichloride)

1,2,4-Trichlorobenzene

1,2,4-Trimethylbenzene

(Pseudocumene)

1,2-Dibromo-3-chloropropane (DBCP, Nemagon)

1,2-Dibromoethane (EDB,

Ethylene dibromide)

1,2-Dichlorobenzene (oDichlorobenzene, 1,2-

DCB)

1,2-Dichloroethane (Ethylene dichloride)

1,3,5-Trimethylbenzene

(Mesitylene)

1,3-Dichlorobenzene (mDichlorobenzene)

1,4-Dichlorobenzene (pDichlorobenzene, 1,4-

DCB)

1-Chloro-2-methylbenzene (o-Chlorotoluene)

1-Chloro-4-methylbenzene (p-Chlorotoluene)

2,2-Dichloropropane

Bromobenzene (Phenyl

bromide)

Bromochloromethane

(Methylene chlorobromide)

Bromomethane (Methyl

bromide)
U.S. Geological Survey C

SUMMARY OF COMPOUND DETECTIONS AND CONCE

1,2-Dimethylnaphthalene

--

7%

1,6-Dimethylnaphthalene

--

26%

1-Methyl-9H-fluorene --

2%

1-Methylphenanthrene

--

10%

1-Methylpyrene --

7%

2,2-Biquinoline --

7%

2,3,6-Trimethylnaphthalene

--

7%

2,6-Dimethylnaphthalene

--

83%

2,6-Dinitrotoluene --

10%

2-Ethylnaphthalene --

5%

2-Methylanthracene --

7%

3,5-Dimethylphenol --

7%

4,5-Methylenenephenanthrene

--

2%

4-Chloro-3-methylphenol

--

5%

9H-Carbazole --

7%

9H-Fluorene --

5%

Acenaphthene --

2%

Concentrations of semivolatile organic compounds, organochlorine compounds, and trace elements detected in fish tissue 

sediment of the Upper Snake River Basin Study Unit. [μg/g, micrograms per gram; μg/kg, micrograms per kilogram; %, per

than; - -, not measured; trade names may vary]

EXPLANATION

Range of detections in fish and clam tissue in all 20 Study Units

Detection in bed sediment or fish tissue in the Upper Snake River Basin Study Unit

Range of detections in bed sediment in all 20 Study Units

Guideline for the protection of aquatic life e

Semivolatile organic

compound

Rate of

detection b

Concentration, in μg/kg

0.1 10 100 1,000 10,000 100,000 1

Semivolatile organic

compound

Rate of

detection b

Concentration, in μg/kg

0.1 10 100 1,1

Acenaphthylene --

7%

Acridine --

5%

Anthracene --

17%

Anthraquinone --

12%

Azobenzene --

2%

Benz[ a ]anthracene --

21%

Benzo[ a ]pyrene --

14%

Benzo[ b ]fluoranthene

--

12%

Benzo[ c ]cinnoline --

5%

Benzo[ ghi ]perylene --

7%

Benzo[ k ]fluoranthene

--

12%

Butylbenzylphthalate --

60%

Chrysene --

24%

Di- n -butylphthalate --

93%

Di- n -octylphthalate --

5%

Dibenz[ a,h ]

anthracene

--

2%

Dibenzothiophene --

5%
30 Water Quality in the Upper Snake River Basin, Idaho and Wyoming, 1992–95

SUMMARY OF COMPOUND DETECTIONS AND CONCENTRATIONS

Diethylphthalate --

29%

Dimethylphthalate --

10%

Fluoranthene --

27%

Indeno[1,2,3- cd ]

pyrene

--

7%

Isophorone --

2%

Isoquinoline --

19%

Naphthalene --

7%

Phenanthrene --

29%

Phenol --

86%

Pyrene --

27%

Quinoline --

5%

bis(2-Ethylhexyl)phthalate

--

98%

p-Cresol --

79%

total-Chlordane 24%

2%

DCPA (dacthal, chlorthal-dimethyl)

4%

0%

p,p’-DDE 83%

29%

total-DDT 83%

29%

Dieldrin (Panoram D31, Octalox)

20%

7%

alpha-HCH (alphaBHC, alpha-lindane)

2%

0%

delta-HCH (deltaBHC)

2%

--

PCB, total 30%

0%

Pentachloroanisole 2%

0%

Toxaphene (camphechlor)

4%

0%

Trace element Rate

of

detection b

Concentration, in μg/g

Arsenic 100%

100%

Cadmium 64%

100%

Chromium 64%

100%

Copper 100%

100%

Lead 36%

100%

Mercury 55%

55%

Nickel 73%

100%

Selenium 73%

100%

Zinc 100%

100%

0.01 0.1 1 10 1

Semivolatile organic

compound

Rate of

detection b

Concentration, in μg/kg

0.1 10 100 1,000 10,000 100,000 1

Organochlorine

compound1

(Trade name)

Rate

of

detection b

Concentration, in μg/kg

0.01 0.1 1 10 100 

1 Some organochlorine compounds and compound breakdown products ar
U.S. Geological Survey C

SUMMARY OF COMPOUND DETECTIONS AND CONCE

Semivolatile organic compounds, organochlorine compounds, and trace elements not detected in fish tissue and bed sedim

Upper Snake River Basin Study Unit.

Semivolatile organic

compounds

1,2,4-Trichlorobenzene

1,2-Dichlorobenzene

(o-Dichlorobenzene,

1,2-DCB)

1,3-Dichlorobenzene

(m-Dichlorobenzene)

1,4-Dichlorobenzene

(p-Dichlorobenzene,

1,4-DCB)

2,4-Dinitrotoluene

2-Chloronaphthalene

2-Chlorophenol

4-Bromophenylphenylether

4-Chlorophenylphenylether

C8-Alkylphenol

N-Nitrosodi-n-propylamine

N-Nitrosodiphenylamine

Nitrobenzene

Pentachloronitrobenzene

Phenanthridine

bis (2-Chloroethoxy)

methane

bis (2-Chloroisopropyl)ether

Organochlorine

compounds

Aldrin (HHDN, Octalene)

Chloroneb (chloronebe,

Demosan, Soil Fungicide

1823)

Endosulfan I (alphaEndosulfan, Thiodan,

Cyclodan, Beosit, Malix,

Thimul, Thifor)

Endrin (Endrine)

Heptachlor epoxide

(Heptachlor metabolite)

Heptachlor (Heptachlore,

Velsicol 104)

Hexachlorobenzene (HCB)

Isodrin (Isodrine,

Compound 711)

Mirex (Dechlorane)

alpha-HCH (alpha-BHC,

alpha-lindane, alphahexachlorocyclohexane,

alpha-benzene hexachloride)

beta-HCH (beta-BHC,

beta-hexachlorocyclohexane, alpha-benzene

hexachloride)

cis-Permethrin (Ambush,

Astro, Pounce, Pramex,

Pertox, Ambushfog, Kafil,

Perthrine, Picket, Picket G,

Dragnet, Talcord,

Outflank, Stockade,

Eksmin, Coopex, Peregin,

Stomoxin, Stomoxin P,

Qamlin, Corsair, Tornade)

gamma-HCH (Lindane,

gamma-BHC, Gammexane, Gexane, Soprocide,

gamma-hexachlorocyclohexane, gamma-benzene

hexachloride, gammabenzene)

o,p’-Methoxychlor

p,p’-Methoxychlor

(Marlate, methoxychlore)

trans-Permethrin(Ambush,

Astro, Pounce, Pramex,

Pertox, Ambushfog, Kafil,

Perthrine, Picket, Picket G,

Dragnet, Talcord, Outflank,

Stockade, Eksmin,

Coopex, Peregin,

Stomoxin, Stomoxin P,

Qamlin, Corsair, Tornade)

Trace elem

No non-detec

a

 Selected water-quality standards and guidelines [29].

b Rates of detection are based on the number of analyses and detections in the Study Unit, not on national data. Rates of detection for h

insecticides were computed by only counting detections equal to or greater than 0.01 μg/L in order to facilitate equal comparisons a

pounds, which had widely varying detection limits. For herbicides and insecticides, a detection rate of “<1%” means that all detecti

0.01 μg/L, or the detection rate rounds to less than 1 percent. For other compound groups, all detections were counted and minimum 

for most compounds were similar to the lower end of the national ranges shown. Method detection limits for all compounds in these 

marized in [29].

c

 Detections of these compounds are reliable, but concentrations are determined with greater uncertainty than for the other compounds 

as estimated values [31].

d The guideline for methyl tert-butyl ether is between 20 and 40 μg/L; if the tentative cancer classification C is accepted, the lifetime hea

be 20 μg/L [29].

e

 Selected sediment-quality guidelines [29].
32 Water Quality in the Upper Snake River Basin, Idaho and Wyoming, 1992–95

REFERENCES

1. Idaho Department of Health and Welfare, 1989, Idaho

water quality status report and nonpoint source assessment, 1988: Boise, Idaho Department of Health and

Welfare, Division of Environmental Quality, 170 p.

2. Maupin, M.A., 1995, Water-quality assessment of the

upper Snake River Basin, Idaho and western Wyoming—environmental setting, 1980–92: U.S. Geological Survey Water-Resources Investigations Report 94–

4221, 35 p.

3. Clark, G.M., 1994, Assessment of selected constituents

in surface water of the upper Snake River Basin, Idaho

and western Wyoming, water years 1975–89: U.S. Geological Survey Water-Resources Investigations Report

93–4229, 49 p.

4. Clark, G.M., 1997, Assessment of nutrients, suspended

sediment, and pesticides in surface water of the upper

Snake River Basin, Idaho and western Wyoming, water

years 1991–95: U.S. Geological Survey WaterResources Investigations Report 97–4020, 45 p.

5. Rupert, M.G., 1997, Nitrate (NO2+NO3–N) in ground

water of the upper Snake River Basin, Idaho and western Wyoming, 1991–95: U.S. Geological Survey WaterResources Investigations Report 97–4174, 47 p.

6. Maret, T.R., 1997, Characteristics of fish assemblages

and related environmental variables for streams of the

upper Snake River Basin, Idaho and western Wyoming,

1993–95: U.S. Geological Survey Water-Resources

Investigations Report 97–4087, 50 p.

7. Maret, T.R., 1995, Water-quality assessment of the

upper Snake River Basin, Idaho and western Wyoming— summary of aquatic biological data for surface

water through 1992: U.S. Geological Survey WaterResources Investigations Report 95–4006, 59 p.

8. Maupin, M.A., 1996, Estimated water use at dairy

farms in Gooding, Jerome, and Twin Falls Counties,

Idaho, 1990–93: U.S. Geological Survey Fact Sheet

FS–111–96, 2 p.

9. Rupert, M.G., 1996, Major sources of nitrogen input

and loss in the upper Snake River Basin, Idaho and

western Wyoming, 1990: U.S. Geological Survey

Water-Resources Investigations Report 96–4008, 15 p.

10. Maret, T.R., and Ott, D.S., 1997, Organochlorine compounds in fish tissue and bed sediment in the upper

Snake River Basin, Idaho and western Wyoming, 1992–

94: U.S. Geological Survey Water-Resources Investigations Report 97–4080, 23 p.

11. Kjelstrom, L.C., 1995, Streamflow gains and losses in

the Snake River and ground-water budgets for the

Snake River Plain, Idaho and eastern Oregon: U.S.

Geological Survey Professional Paper 1408–C, 47 p.

12. Idaho Department of Water Resources, 1990, Snake

River and tributaries above Milner, Idaho: Idaho Falls,

Watermasters Report, Water District No. 1, 391 p.

13. Rupert, M.G., 1994, Analysis of data on nutrien

organic compounds in ground water in the uppe

River Basin, Idaho and western Wyoming, 198

U.S. Geological Survey Water-Resources Invest

Report 94–4135, 40 p.

14. Maret, T.R., Robinson, C.T., and Minshall, G.W

Fish assemblages and environmental correlates 

disturbed streams of the upper Snake River Bas

Transactions of the American Fisheries Society

no. 2, p. 200–216.

15. U.S. Department of Health and Human Service

Surveillance for waterborne-disease outbreaks, 

States, 1993–1994: U.S. Department of Health 

Human Services, Centers for Disease Control a

vention, Morbidity and Mortality Weekly Repo

no. SS–1.

16. Mueller, D.K., Hamilton, P.A., Helsel, D.R., Hi

and Ruddy, B.C., 1995, Nutrients in ground wa

surface water of the United States—an analysis 

through 1992: U.S. Geological Survey Water-Re

Investigations Report 95–4031, 74 p.

17. Clark, G.M., and Ott, D.S., 1996, Springflow ef

chemical loads in the Snake River, south-centra

American Water Resources Association, Water

Resources Bulletin, v. 32, no. 3, p. 553–563.

18. Nolan, B.T, and Ruddy, B.C., 1996, Nitrate in g

waters of the United States—assessing the risk

Geological Survey Fact Sheet FS–092–96, 4 p.

19. U.S. Geological Survey, 1997, Pesticides in sur

waters—current understanding of distribution a

major influences: U.S. Geological Survey Fact 

FS–039–97, 4 p.

20. Clark, G.M., 1997, Occurrence and flux of sele

ticides in surface water of the upper Snake Rive

Idaho and western Wyoming: Ankeny, Iowa, Jo

Soil and Water Conservation, v. 52, no. 5, p. 38

21. Yankey, Rich, Potter, Sue, Maret, Terry, McLau

Jim, Carter, Dave, Brockway, Charles, Jesser, R

Olmstead, Brian, 1991, Rock Creek Rural Clea

Program final report, 1981–1991: Boise, Idaho 

ment of Health and Welfare, Division of Enviro

Quality, 328 p.

22. Clark, G.M., 1994, Occurrence of pesticides in 

water in the Rock Creek watershed, south-centr

Idaho: Moscow, Journal of the Idaho Academy 

ence, v. 30, no. 2, p. 61–74.

23. U.S. Environmental Protection Agency, 1992, Na

study of chemical residues in fish: Washington, D

Environmental Protection Agency, Office of Scie

Technology, 2 v. (EPA–823–R–92–008a, 166 p., 

EPA–823–R–92–008b, 2 apps. [about 200 pages

24. National Academy of Sciences and National A

of Engineering, 1973, Water quality criteria, 19
U.S. Geological Survey Circula

REFER

Washington, D.C., U.S. Government Printing Office,

594 p.

25. Smith, J.S., Witkowski, P.J., and Fusillo, T.V., 1988,

Manmade organic compounds in the surface waters of

the United States—a review of current understanding:

U.S. Geological Survey Circular 1007, 92 p.

26. Rupert, M.G., Stone, M.A.J., and Ott, D.S., 1995,

National Water-Quality Assessment Program—nitrate

and pesticides in ground water, Blaine, Cassia, Lincoln,

and Minidoka Counties, south-central Idaho: U.S. Geological Survey Fact Sheet FS–246–95, 4 p.

27. Idaho Division of Environmental Quality, 1996, The

Middle Snake River Watershed Management

Plan—Phase 1 TMDL, total phosphorus: Twin Falls,

Idaho Division of Environmental Quality, Public

Review Draft no. 2, 226 p.

28. U.S. Fish and Wildlife Service, 1995, Snake River

Aquatic Species Recovery Plan: Boise, U.S. Fi

Wildlife Service, Snake River Basin Office, Ec

Services, 92 p.

29. Gilliom, R.J., Mueller, D.K., and Nowell, L.H., 

Methods for comparing water-quality condition

National Water-Quality Assessment Study Unit

1995: U.S. Geological Survey Open-File Repor

589.

30. Omernik, J.M., and Gallant, A.L., 1986, Ecoregio

Pacific Northwest: Corvallis, Oreg., U.S. Environ

Protection Agency EPA/600/3–86/033, 39 p.

31. Zaugg, S.D., Sandstrom, M.W., Smith, S.G., and F

K.M., 1995, Methods of analysis by the U.S. Geo

Survey National Water Quality Laboratory— Det

tion of pesticides in water by C-18 solid-phase ex

and capillary-column gas chromatography/mass s

etry with selected-ion monitoring: U.S. Geologica

Open-File Report 95–181, 49 p.
34 Water Quality in the Upper Snake River Basin, Idaho and Wyoming, 1992–95

GLOSSARY

The terms in this glossary were compiled from numerous

sources. Some definitions have been modified and may not be

the only valid ones for these terms.

Acre-foot - A volume of water equal to 1 foot in depth and

covering 1 acre; equivalent to 43,560 cubic feet or

325,851 gallons.

Algae - Chlorophyll-bearing, nonvascular, primarily aquatic

species that have no true roots, stems, or leaves; most

algae are microscopic, but some species can be as large

as vascular plants.

Alluvial aquifer - A water-bearing deposit of unconsolidated material (sand and gravel) left behind by a river or

other flowing water.

Anthropogenic - Occurring because of, or influenced by,

human activity.

Aquatic-life criteria - Water-quality guidelines for protection of aquatic life. Often refers to U.S. Environmental

Protection Agency water-quality criteria for protection

of aquatic organisms. See also Water-quality guidelines,

Water-quality criteria.

Aquifer - A water-bearing layer of soil, sand, gravel, or rock

that will yield usable quantities of water to a well.

Bed sediment - The material that temporarily is stationary in

the bottom of a stream or other watercourse.

Benthic invertebrates - Insects, mollusks, crustaceans,

worms, and other organisms without a backbone that

live in, on, or near the bottom of lakes, streams, or

oceans.

Breakdown product - A compound derived by chemical,

biological, or physical action upon a pesticide. The

breakdown is a natural process which may result in a

more toxic or a less toxic compound and a more persistent or less persistent compound.

Concentration - The amount or mass of a substance present

in a given volume or mass of sample. Usually expressed

as micrograms per liter (water sample) or micrograms

per kilogram (sediment or tissue sample).

Consumptive use - The quantity of water that is not available for immediate reuse because it has been evaporated, transpired, or incorporated into products, plant

tissue, or animal tissue. Also referred to as “water consumption.”

Criterion - A standard rule or test on which a judgment or

decision can be based.

Cubic foot per second - (ft3/s, or cfs) rate of water discharge

representing a volume of 1 cubic foot passing a given

point during 1 second, equivalent to approximately 7.48

gallons per second or 448.8 gallons per minute or

0.02832 cubic meter per second.

Discharge - Rate of fluid flow passing a given point at a

given moment in time, expressed as volume per unit of

time.

Dissolved solids - Amount of minerals, such as salt, 

dissolved in water; amount of dissolved solids 

indicator of salinity or hardness.

Drainage basin - The portion of the surface of the E

contributes water to a stream through overland 

including tributaries and impoundments.

Drinking-water standard or guideline - A thresho

centration in a public drinking-water supply, de

to protect human health. As defined here, stand

U.S. Environmental Protection Agency regulati

specify the maximum contamination levels for 

water systems required to protect the public we

guidelines have no regulatory status and are issu

advisory capacity.

Ecoregion - An area of similar climate, landform, so

potential natural vegetation, hydrology, or othe

ically relevant variables.

Eutrophication - The process by which water becom

enriched with plant nutrients, most commonly p

rus and nitrogen.

Health advisory - Nonregulatory levels of contamin

drinking water that may be used as guidance in 

absence of regulatory limits. Advisories consis

mates of concentrations that would result in no 

or anticipated health effects (for carcinogens, a 

fied cancer risk) determined for a child or for a

for various exposure periods.

Herbicide - A chemical or other agent applied for th

pose of killing undesirable plants. See also Pes

Insecticide - A substance or mixture of substances i

to destroy or repel insects. See also Pesticide.

Load - General term that refers to a material or cons

in solution, in suspension, or in transport; usua

expressed in terms of mass or volume.

Major ions - Constituents commonly present in con

tions exceeding 1.0 milligram per liter. Dissolv

ions generally are calcium, magnesium, sodium

potassium; the major anions are sulfate, chlorid

ride, nitrate, and those contributing to alkalinity

generally assumed to be bicarbonate and carbo

Mouth - The place where a stream discharges to a la

stream, a lake, or the sea.

National Academy of Sciences/National Academy 

Engineering (NAS/NAE) recommended max

concentration in water - Numerical guideline

mended by two joint NAS/NAE committees for 

tection of freshwater and marine aquatic life, re

tively. These guidelines were based on available 

toxicity studies and were considered preliminar

when formulated (1972). The guidelines used i

summary reports are for freshwater.

Nonpoint source - A pollution source that cannot be 

as originating from discrete points such as pipe 

charge. Areas of fertilizer and pesticide applica
U.S. Geological Survey Circula

GLO

atmospheric deposition, manure, and natural inputs

from plants and trees are types of nonpoint source pollution.

Organochlorine compound - Synthetic organic compounds

containing chlorine. As generally used, term refers to

compounds containing mostly or exclusively carbon,

hydrogen, and chlorine. Examples include organochlorine insecticides, polychlorinated biphenyls, and some

solvents containing chlorine.

Pesticide - A chemical applied to crops, rights of way,

lawns, or residences to control weeds, insects, fungi,

nematodes, rodents, or other “pests.”

Point source - A source at a discrete location such as a discharge pipe, drainage ditch, tunnel, well, concentrated

livestock operation, or floating craft.

Polychlorinated biphenyls (PCBs) - A mixture of chlorinated derivatives of biphenyl, marketed under the trade

name Aroclor with a number designating the chlorine

content (such as Aroclor 1260). PCBs were used in

transformers and capacitors for insulating purposes and

in gas pipeline systems as a lubricant. Further sale for

new use was banned by law in 1979.

Radon - A naturally occurring, colorless, odorless, radioactive gas formed by the disintegration of the element

radium; damaging to human lungs when inhaled.

Riparian - Areas adjacent to rivers and streams with a high

density, diversity, and productivity of plant and animal

species relative to nearby uplands.

Runoff - Rainwater or snowmelt that is transported to

streams by overland flow, tile drains, or ground water.

Sediment - Particles, derived from rocks or biological materials, that have been transported by a fluid or other natural process and are suspended or settled in water.

Semivolatile organic compounds (SVOCs) - Operationally

defined as a group of synthetic organic compounds that

are solvent-extractable and can be determined by gas

chromatography/mass spectrometry. SVOCs include

phenols, phthalates, and polycyclic aromatic hydrocarbons (PAHs).

Streamflow - A type of channel flow, applied to that part of

surface runoff in a stream whether or not it is affected

by diversion or regulation.

Suspended sediment - Particles of rock, sand, soil, 

organic detritus carried in suspension in the wa

umn, in contrast to sediment that moves on or n

streambed.

Tolerant species - Those species that are adaptable 

ant of) human effects on the environment.

Trace element - An element found in only minor am

(concentrations less than 1.0 milligram per liter

water or sediment; includes arsenic, cadmium, 

mium, copper, lead, mercury, nickel, and zinc.

Volatile organic compounds (VOCs) - Organic che

that have a high vapor pressure relative to their 

solubility. VOCs include components of gasolin

oils, and lubricants, as well as organic solvents

gants, some inert ingredients in pesticides, and 

byproducts of chlorine disinfection.

Water-quality criteria - Specific levels of water qu

which, if reached, are expected to render a bod

water unsuitable for its designated use. Commo

refers to water-quality criteria established by th

Environmental Protection Agency. Water-quali

ria are based on specific levels of pollutants tha

make the water harmful if used for drinking, sw

farming, fish production, or industrial processe

Water-quality guidelines - Specific levels of water 

which, if reached, may adversely affect human h

aquatic life. These are nonenforceable guideline

by a governmental agency or other institution.

Water-quality standards - State-adopted and U.S. 

mental Protection Agency-approved ambient st

for water bodies. Standards include the use of th

body and the water-quality criteria that must be 

protect the designated use or uses.

Water year - The continuous 12-month period, Oct

through September 30, in U.S. Geological Surv

reports dealing with the surface-water supply. T

water year is designated by the calendar year in 

ends and which includes 9 of the 12 months. Th

year ending September 30, 1980, is referred to 

“1980” water year.
Clark and others • Water Quality in the Upper Snake River Basin

 USGS Circular 1160 • 1998

National Water-Quality Assessment (NAWQA) Program

Upper Snake River Basin

NAWQA

Twin

Falls

Idaho

Falls

Snake River

IDAHO

NEVADA UTAH

IDAHO

WYOMING Jackson

Lake Henrys Fork

Snake

River

Pocatello

Big Lost R iver