Water Quality in the

Yellowstone River Basin

Wyoming, Montana, and North Dakota, 1999–2001

U.S. Department of the Interior

U.S. Geological Survey

Circular 1234
Points of Contact and Additional Information

The companion Web site for NAWQA summary reports:

http://water.usgs.gov/nawqa/nawqa_sumr.html

Other NAWQA summary reports

River Basin Assessments

Acadian-Pontchartrain Drainages (Circular 1232)

Albemarle-Pamlico Drainage Basin (Circular 1157)

Allegheny and Monongahela River Basins (Circular 1202)

Apalachicola-Chattahoochee-Flint River Basin (Circular 1164)

Central Arizona Basins (Circular 1213)

Central Columbia Plateau (Circular 1144)

Central Nebraska Basins (Circular 1163)

Connecticut, Housatonic and Thames River Basins (Circular 1155)

Cook Inlet Basin (Circular 1240)

Delaware River Basin (Circular 1227)

Delmarva Peninsula (Circular 1228)

Eastern Iowa Basins (Circular 1210)

Georgia-Florida Coastal Plain (Circular 1151)

Great and Little Miami River Basins (Circular 1229) 

Great Salt Lake Basins (Circular 1236)

Hudson River Basin (Circular 1165)

Island of Oahu (Circular 1239)

Kanawha - New River Basins (Circular 1204)

Lake Erie - Lake Saint Clair Drainages (Circular 1203)

Long Island - New Jersey Coastal Drainages (Circular 1201)

Lower Illinois River Basin (Circular 1209)

Lower Susquehanna River Basin (Circular 1168)

Lower Tennessee River Basin (Circular 1233)

Las Vegas Valley Area and the Carson and Truckee River Basins (Circular 1170)

Mississippi Embayment (Circular 1208)

Mobile River Basin (Circular 1231)

New England Coastal Basins (Circular 1226)

Northern Rockies Intermontane Basins (Circular 1235)

Ozark Plateaus (Circular 1158)

Potomac River Basin (Circular 1166)

Puget Sound Basin (Circular 1216)

Red River of the North Basin (Circular 1169)

Rio Grande Valley (Circular 1162)

Sacramento River Basin (Circular 1215)

San Joaquin-Tulare Basins (Circular 1159)

Santa Ana Basin (Circular 1238)

Santee River Basin and Coastal Drainages (Circular 1206)

South-Central Texas (Circular 1212)

South Platte River Basin (Circular 1167)

Southern Florida (Circular 1207)

Trinity River Basin (Circular 1171)

Upper Colorado River Basin (Circular 1214)

Upper Illinois River Basin (Circular 1230)

Upper Mississippi River Basin (Circular 1211)

Upper Snake River Basin (Circular 1160)

Upper Tennessee River Basin (Circular 1205)

Western Lake Michigan Drainages (Circular 1156)

White River Basin (Circular 1150)

Willamette Basin (Circular 1161)

Yakima River Basin (Circular 1237)

National Assessments

The Quality of Our Nation‘s Waters—Nutrients and Pesticides (Circular 1225)

Yellowstone River Basin contact and Web site:

USGS State Representative

U.S. Geological Survey

Water Resources Discipline

2617 E. Lincolnway, Suite B

Cheyenne, Wyoming 82001

e-mail: state_rep_wy@usgs.gov

http://wy.water.usgs.gov/YELL/

National NAWQA Program:

Chief, NAWQA Program

U.S. Geological Survey

Water Resources Division

12201 Sunrise Valley Drive, M.S. 413

Reston, VA 20192

http://water.usgs.gov/nawqa/

Front cover: Aerial image of Yellowstone River and Emigrant Peak in Paradise Valley, near Livingston, Mont. (used with permission 

from Larry Mayer, larrymayer.com). 

Back cover: Left, hydrologist in field vehicle, filtering water samples for analysis of organic compounds (photograph by Gregory K. 

Boughton, USGS); right, scientist collecting a depth- and width-integrated sample from the Bighorn River near Greybull, Wyo. 

(photograph by Nate Majerus, USGS). 
U.S. Department of the Interior

U.S. Geological Survey

Water Quality in the Yellowstone River Basin, 

Wyoming, Montana, and North Dakota,

1999–2001

By David A. Peterson, Kirk A. Miller, Timothy T. Bartos, Melanie L. Clark,

Stephen D. Porter, and Thomas L. Quinn

Circular 1234
U.S. Department of the Interior

Gale A. Norton, Secretary

U.S. Geological Survey

Charles G. Groat, Director

U.S. Geological Survey, Reston, Virginia: 2004

For sale by U.S. Geological Survey, Information Services

Box 25286, Denver Federal Center

Denver, CO 80225

For more information about the USGS and its products:

Telephone: 1-888-ASK-USGS

World Wide Web: http://www.usgs.gov/

Any use of trade, product, or firm names in this publication is for descriptive purposes only and does not imply 

endorsement by the U.S. Government.

Although this report is in the public domain, permission must be secured from the individual copyright owners to 

reproduce any copyrighted materials contained within this report.

Suggested citation:

Peterson, David A., Miller, Kirk A., Bartos, Timothy T., Clark, Malanie L., Porter, Stephen D., and Quinn, Thomas L.., 

2004, Water quality in the Yellowstone River Basin, Wyoming, Montana, and North Dakota, 1999–2001: Reston, Va., 

U.S. Geological Survey Circular 1234, 40 p.

Library of Congress Cataloging-in-Publication Data

Water quality in the Yellowstone River Basin, Wyoming, Montana, and North Dakota, 1999–2001 / 

 by David A. Peterson ... [et. al.].

 p. cm. -- (Circular ; 1234)

 Includes bibliographical references.

 ISBN 0-607-92652-2

 1. Water quality -- Yellowstone River Watershed. I. Peterson, David A. (David Allen), 1955-

 II. Geological Survey (U.S.) III. U.S. Geological Survey circular ; 1234.

 TD225.Y37W38 2003

 363.739’42’0978--dc22 2003063149
iii

Contents

National Water-Quality Assessment Program ......................................................... iv

What kind of water-quality information does the NAWQA Program provide? ............... v

Introduction to this Report .............................................................................. vi

Summary of Major Findings .............................................................................. 1

Stream and River Highlights ..................................................................... 1

Ground-Water Highlights ........................................................................... 2

Introduction to the Yellowstone River Basin ......................................................... 3

Surface-Water Resources ........................................................................ 4

Ground-Water Resources ........................................................................ 5

Biological Resources .............................................................................. 5

Water-Quality Issues .............................................................................. 5

Major Findings ............................................................................................. 6

Natural factors affect stream and ground-water chemistry ................................. 6

Coliform bacteria concentrations exceeded Federal guidelines frequently in streams,

but rarely in ground water ............................................................... 7

Nutrient concentrations vary seasonally and in relation to land use ........................ 9

Pesticides were detected frequently in streams, ground water, and fish tissue, but at

low concentrations ........................................................................ 13

Commonly detected volatile organic compounds in Quaternary aquifers are associated 

with gasoline .............................................................................. 18

Ground water underlying low-density development generally is suitable for domestic

use .......................................................................................... 18

Some trace element concentrations in streams and bed sediment exceeded aquatic-life 

guidelines ................................................................................. 18

Trace elements in ground water were generally low compared to drinking-water

standards and guidelines ............................................................... 20

Periphyton and invertebrate communities are degraded in some segments of the

Yellowstone River ........................................................................ 20

Fish communities reflect water-quality and habitat conditions .............................. 22

Study Unit Design ....................................................................................... 23

References Cited .......................................................................................... 25

Glossary ................................................................................................... 28

Appendix—Water-Quality Data from the Yellowstone River Basin in a National Context ...... 29
National Water-Quality Assessment Program

The quality of the Nation’s water resources is integrally linked to the long-term availability of 

water that is clean and safe for drinking and recreation and also suitable for industry, irrigation, 

and habitat for fish and wildlife. Recognizing the need for long-term, nationwide assessments 

of water resources, the U.S. Congress has appropriated funds since 1991 for the USGS to conduct the National Water-Quality Assessment (NAWQA) Program. Scientists in the NAWQA 

Program work with partners in government, research, and public interest groups to assess the 

status and spatial extent of water-quality conditions, how water quality changes with time, 

and how human activities and natural factors affect water quality. This information is useful 

for guiding water-management and protection strategies, research, and monitoring in different 

hydrologic and land-use settings across the Nation.

The Yellowstone River Basin is one of 51 water-quality assessments initiated since 1991. 

Together, the 51 major river basins and aquifer systems, referred to as “Study Units,” include 

water resources used by more than 60 percent of the population in watersheds that cover about 

half of the land areas of the conterminous United States. Timing of the assessments varies 

because of the Program’s rotational design, in which one-third of all Study Units are intensively 

investigated for 3 to 4 years, with trends assessed every 10 years. As indicated on the map, the 

Yellowstone River Basin is part of the third set of intensive investigations, which began in 1997.

1991–95

1994–98

1997–2001

Not yet scheduled

HighPlains Regional

GroundWaterStudy,

1999–2004

NAWQA Study Units—

Assessment schedule

Yellowstone River Basin

iv
What kind of water-quality information does the NAWQA 

Program provide?

Water-quality assessments by a single program cannot possibly address all of the Nation’s 

water-resources needs and issues. Therefore, it is necessary to define the context within which 

NAWQA information is most useful. 

• Total resource assessment—NAWQA assessments are long-term and interdisciplinary, 

and include information on water chemistry, hydrology, land use, stream habitat, and 

aquatic life. Assessments are not limited to a specific geographic area or water-resource 

problem at a specific time. Therefore, the findings describe the general health of the total 

water resource, as well as emerging water issues, thereby helping managers and decision 

makers to set priorities.

• Source-water characterization—Assessments focus on the quality of the available, 

untreated resource and thereby complement (rather than duplicate) Federal, State, and 

local programs that monitor drinking water. Findings are compared to drinking-water 

standards, guidelines for the protection of aquatic life, and health advisories as a way to 

characterize the resource.

• Compounds studied—Assessments focus on chemical compounds that have well-established methods of investigation. It is not financially or technically feasible to assess all 

the contaminants in our Nation’s waters. In general, the NAWQA Program investigates 

those pesticides, nutrients, volatile organic compounds, and metals that have been or are 

currently used commonly in agricultural and urban areas across the Nation. A complete 

list of compounds studied is on the NAWQA Web site at http://water.usgs.gov/nawqa.

• Detection compared to risk—Compounds are measured at very low concentrations, 

often 10 to 100 times lower than Federal or State standards and health advisories. Detection of compounds, therefore, does not necessarily translate to risks to human health or 

aquatic life. However, these analyses are useful for identifying and evaluating emerging 

issues, as well as for tracking contaminant levels over time.

• Multiple scales—Assessments are guided by a nationally consistent study design and 

uniform methods of sampling and analysis. Findings thereby pertain not only to water 

quality of a particular stream or aquifer, but also contribute to the larger picture of how 

and why water quality varies regionally and nationally. This consistent, multiscale 

approach helps to determine if a water-quality issue is isolated or pervasive. It also 

allows direct comparisons of how human activities and natural processes affect water 

quality in the Nation’s diverse environmental settings. 

v
Yellowstone Lake in Yellowstone National Park

(photograph by Gregory K. Boughton, U.S. Geological Survey).

vi

Introduction to this Report

This report contains the major findings of a 1999–2001 assessment of water quality in the 

Yellowstone River Basin. It is one of a series of reports by the National Water-Quality Assessment (NAWQA) Program that present major findings in 51 major river basins and aquifer 

systems across the Nation. 

In these reports, water quality is discussed in terms of local, State, and regional issues. Conditions in a particular basin or aquifer system are compared to conditions found elsewhere and 

to selected national benchmarks, such as those for drinking-water quality and the protection of 

aquatic organisms. 

This report is intended for individuals working with water-resource issues in Federal, State, or 

local agencies, universities, public interest groups, or in the private sector. The information will 

be useful in addressing a number of current issues, such as the effects of agricultural and urban 

land use on water quality, human health, drinking water, source-water protection, hypoxia and 

excessive growth of algae and plants, pesticide registration, and monitoring and sampling strategies. This report also is for individuals who wish to know more about the quality of streams 

and ground water in areas near where they live, and how that water quality compares to the 

quality of water in other areas across the Nation.

The water-quality conditions in the Yellowstone River Basin summarized in this report are 

discussed in detail in other reports that can be accessed from http://wy.water.usgs.gov/YELL/

index.htm. Detailed technical information, data and analyses, collection and analytical methodology, models, graphs, and maps that support the findings presented in this report, in addition 

to reports in this series from other basins, can be accessed from the national NAWQA Web site 

(http://water.usgs.gov/nawqa). 

“The Yellowstone River 

Basin NAWQA program has 

been beneficial to the State of 

Wyoming, particularly to the 

Department of Environmental 

Quality’s water-quality monitoring and assessment efforts.

“The ecological, bacteria, 

water-quality, and streamflow 

data collected have provided 

DEQ with the ability to assess 

the water quality much more 

comprehensively than what 

would be possible with DEQ 

data alone.”

Jeremy Zumberge, Monitoring

Program Supervisor, Wyoming 

Department of Environmental Quality

“Information provided by the 

Yellowstone NAWQA project 

has been very useful to our 

program. The Yellowstone 

River periphyton study results 

are a fundamental aspect of 

DEQ’s fish and aquatic life 

use impairment determinations and a foundation for 

nutrient total maximum daily 

loads (TMDL) development.

“NAWQA Powder River data 

have been a critical part of 

trend analysis work. Without 

that data, we would have had 

very little recent information.”

Pat Newby, Water Quality Specialist, 

Montana Department of

Environmental Quality
The Yellowstone River Basin covers 70,000 square miles in 

Wyoming, Montana, and North Dakota. Population in the basin 

is about 320,000; most communities are along river valleys in the 

plains. Ninety-eight percent of the water used in the basin is for 

irrigated crops. Ground water for domestic use in rural areas 

typically comes from shallow wells completed in Quaternary and 

Tertiary aquifers.

Rive

M rissouri

Yellowstone

Boysen Reservoir

Bighorn

Lake Res

Tongue River

Yellowstone Lake

Tongue

Powder

River

River

River

Clarks

Bighorn

River

River Wind

Shoshone

River

Fork

Litt w l o e P

der R

Salt Cr

104°

107°

110°

47°

44°

0 40 80 KILOMETERS

Yellowstone

National

Park

MONTANA

WYOMING

N

O

RTH

D

A

KOTA

Billings

Sidney

Lander

Livingston

Corwin

Springs

Forsyth

Sheridan

Cody

Gillette

Riverton

Red Lodge

Miles

City

EXPLANATION

Water, perennial ice and

snow, or barren

Agricultural or developed

Grass and shrubland

Forested

Bighorn Mountains

Wind River Range

Absaroka Range

Beartooth

Mountains

0 40 80 MILES

Land cover and land use MONTANA

WYOMING

Yellowstone

River

Basin

NORTH

DAKOTA

Summary of Major Findings

1

Stream and River Highlights

The water quality of streams in the Yellowstone River 

Basin largely is influenced by natural factors. Factors such 

as geology and climate can cause concentrations of dissolved 

solids, nutrients, and trace elements in streams to exceed 

guidelines for protection of human health and aquatic life. 

Although human activities also can influence concentrations 

of those same water-quality characteristics, concentrations of 

manufactured compounds such as pesticides generally were 

low in streams, fish tissue, and bed sediment compared to 

levels measured in other NAWQA Program studies across the 

Nation. Human activities also can influence concentrations of 

bacteria and aquatic biological communities.

• Concentrations of fecal coliform bacteria and Escherichia 

coli, which are indicators of fecal matter from warmblooded animals, were higher in urban and agricultural 

streams than in forested or rangeland streams. Almost 

40 percent of bacteria concentrations exceeded the Federal 

recreational criterion for moderate use (p. 7).

Major Influences on Streams

• Geology and land use (percentage of

rangeland in the drainage area)

• Runoff and ground-water discharge from 

residential and agricultural areas

• Drought

Trends in Surface-Water Quality

A trend of increasing concentrations of sodium, chloride, 

and sodium-absorption ratio in the Powder River during 1968 

to 1988 was described by Cary (1991). A mathematical model 

of the Powder River indicated dissolved-solids concentrations 

were influenced by discharge of oil-production water to a 

tributary, Salt Creek, during 1975 to 1988 (Lindner-Lunsford 

and others, 1992). Although discharge of oil-production water 

to Salt Creek has been reduced since 1988, the Powder River 

is currently (2003) of interest because of potential effects to 

water quality from discharge of water related to development 

of coalbed methane for energy supplies. 

• Concentrations of total phosphorus in streams in the 

basins and plains, such as the Clarks Fork Yellowstone, 

Little Powder, and Powder Rivers, were elevated compared to those measured in other streams across the 

Nation, due in part to natural sources (p. 12). Phosphorus concentrations at most sampling sites exceeded the 

Federal goal of 0.1 milligram per liter for minimizing 

nuisance plant growth in flowing waters.

• Herbicides and their breakdown products were detected 

frequently in streams, but at low concentrations compared 

to national levels (p. 15). Organochlorine compounds 

were detected in many fish tissue samples and in one bedsediment sample; concentrations generally were less than 

guidelines for the protection of wildlife (p. 16).

• Concentrations of trace elements in surface and ground 

water generally were less than guidelines for human 

health, but concentrations of selenium in some water 

samples indicated possible adverse effects to biota. Traceelement concentrations in bed sediment from mineralized 

areas (rock formations with high concentrations of minerals and trace elements) exceeded background levels and 

were large enough to possibly affect aquatic life (p. 18). 

• Biological communities are degraded in some segments of 

the Yellowstone River. Algal, invertebrate, and fish communities in the segments near Billings and Forsyth were 

most affected (p. 20).
Small Streams Major Rivers

Mineralized Undeveloped

Selected Indicators of Stream-Water Quality

Mixed

Land Uses

—

Nitrate

Total

phosphorus

Herbicides

Insecticides

Organo- chlorines in fish tissue2

Proportion of samples with detected concentrations

greater than or equal to health-related Federal

guidelines for drinking water, protection of aquatic life, or

the desired goal for preventing nuisance plant growth

Proportion of samples with detected concentrations less

than health-related Federal guidelines for drinking

water, protection of aquatic life, or the desired goal for

preventing nuisance plant growth

Proportion of samples with no detections

Not assessed

— —

— —

1 Arsenic, mercury, and metals.

2 DDT and PCBs.

Trace elements in sediment1

Selected Indicators of Ground-Water Quality

Nitrate

Arsenic

Herbicides

Insecticides

Radon

Proportion of samples with detected concentrations

greater than or equal to health-related Federal guidelines for drinking water

Proportion of samples with detected concentrations less

than health-related Federal guidelines for drinking water

Proportion of samples with no detections

During the 1950s, water quality and aquatic life in the 

Yellowstone River were severely degraded by wastewater 

discharges from towns along the river (Bahls, 1976). Waterquality and biological conditions in the Yellowstone River 

improved during the 1970s, corresponding with improvements 

in wastewater-treatment practices. Biological conditions in the 

Yellowstone River in 2000 (p. 20) remain somewhat degraded, 

but not to the extent described by Bahls (1976).

• Concentrations of bacteria, nitrate, and trace elements 

in ground water generally were less than human-health 

guidelines. Less than 10 percent of the measured nitrate 

concentrations exceeded the Federal drinking-water standard of 10 milligrams per liter (p. 13).

• Pesticides were detected more often in the shallow 

Quaternary aquifers than in the underlying lower Tertiary aquifers. The pesticides most frequently detected in 

ground water were atrazine and prometon (p. 14).

• Volatile organic compounds, many of which are associated 

with gasoline, were detected frequently in samples from 

the Quaternary aquifers and, to a lesser extent, the lower 

Tertiary aquifers. The concentrations were low compared 

to Federal drinking-water standards (p. 18).

Ground-Water Highlights

Natural factors such as geology, aquifer properties, 

and ground-water recharge rates influence concentrations of 

dissolved solids, radon, trace elements, and other aspects of 

ground-water quality. Concentrations of dissolved solids in 

water samples from the Quaternary aquifers and lower Tertiary 

aquifers in the Yellowstone River Basin frequently exceeded 

the Federal secondary drinking-water guideline of 500 milligrams per liter. Low-density developments, often referred to 

as “rural ranchettes,” affect ground-water quality, but the water 

generally is suitable for domestic use.

• Concentrations of radon in 52 of 54 ground-water samples 

exceeded a proposed Federal drinking-water standard of 

300 picocuries per liter. The radon concentrations also 

were high compared to those measured in other groundwater systems measured across the Nation (p. 9).

Trends in Ground-Water Quality

Many of the wells sampled for this study were new, so 

historical data are not available. The data collected in this 

study, however, will serve as a baseline against which any 

future changes in ground-water quality can be measured. In 

the rural ranchette study, age-dating techniques indicated 

much of the water was recharged in the early 1990s or earlier, 

so effects over the last 10 years may not be reflected in the 

samples collected in 2001 (p. 18). Continued monitoring is 

needed to track the effects of increasing development over 

time.

Major Influences on Ground Water

• Geology

• Aquifer properties

• Irrigation

• Rural development

2 Water Quality in the Yellowstone River Basin, Wyoming, Montana, and North Dakota, 1999–2001
Figure 1. The Yellowstone River drains nearly 70,000 square miles, including the Nation’s first national park, vast areas of grass and 

shrubland in the northwestern Great Plains and Wyoming Basin, forested areas in the Rocky Mountains, and small population centers, 

such as Billings, Montana.

104°

107°

110°

47°

44°

Rive

M r

issouri

Yellowstone

Boysen Reservoir

Bighorn Lake Res

Tongue River

Yellowstone Lake

Tongue

Powder

River River

River

Clarks

Bighorn

River

River

Wind

Shoshone

River

Fork

Northwestern Great Plains

EXPLANATION

Middle Rockies

Wyoming Basin

Montana Valley and Foothill Prairies

Quaternary unconsolidated deposits

EXPLANATION

Tertiary sedimentary

rocks

Generalized geology and selected structural features

(modified from Zelt and others, 1999).

Ecoregions (modified from Omernik, 1987).

POWDER

RIVER

BASIN

CEDAR

CREEK

ANTICLINE

PORCUPINE

DOME

WILLISTON

BASIN

CASPER

ARCH

OWL CREEK

MILES CITY ARCH

BIGHORN

BASIN

REED POINT

SYNCLINE

BILLINGS

ARCH

PRYOR

MOU

BULL

BAS

NTAINS

IN

M

CRAZY

B

TNS

ASIN

BEARTOOTH

MOUNTAINS

YELLOWSTONE-ABSAROKA

VOLCANIC GROUP

WIND RIVER RANGE

WIND RIVER BASIN

BIGHORN

MOUNTA

NI S

MTNS

MTNS

Yellowstone

National Park

MONTANA

WYOMING

N

O

RT

H

DA

KOTA

Billings

Red

Lodge

Sidney

Lander

Livingston

Corwin Springs

Forsyth

Sheridan

Cody

Gillette

Riverton

0 20 40 60 KILOMETERS

0 20 40 60 MILES

Miles City

Shaded relief modified from U.S. Geological

Survey digital elevation data, 30-arc seconds,

1995

Base modified from U.S. Geological Survey

digital data, 1:2,000,000, 1972

Albers Equal-Area conic projection

Standard parallels 29°30′ and 45°30′,

central meridian -107°30′

Alfalfa, sugar beets, and other irrigated crops, 

grown in about 4 percent of the basin, are common 

in the river valleys and adjacent areas (photograph 

by Ronald B. Zelt, U.S. Geological Survey).

Diversion dams for irrigation canals along 

the middle and lower Yellowstone River are 

popular fishing spots but can impair fish 

movement upstream (Graham and others, 

1979) (photograph by David A. Peterson,

U.S. Geological Survey).

French voyagers called the Yellowstone River “Roche Jaune,” which 

was translated as “Yellowstone” in 

the journals of the 1805 Lewis and 

Clark expedition (Linford, 1975)

(photograph by Suzanne C. Roberts,

U.S. Geological Survey).

Introduction to the Yellowstone River Basin

3

From its headwaters in Yellowstone National 

Park and surrounding wilderness areas in Wyoming, 

the Yellowstone River flows more than 700 miles 

through Montana to its mouth at the Missouri River 

in North Dakota (fig. 1). Population density in the 

70,000-square-mile basin is sparse, about five people 

per square mile on average. The largest city is Billings, 

Mont. (metropolitan-area population of about 127,000 

in 1999).
Public and domestic use, surface water

and ground water 61 million gallons

per day

—

Industrial use, surface water and

ground water—12 million gallons

per day

Irrigation use, ground water—

42 million gallons per day

Irrigation, surface water

6,337 million gallons

per day

−

Other uses,

surface water

and ground water—

115 million gallons per day

Range (minimum to maximum) of historical data 1928–2001

Mean of historical daily streamflow 1928–2001

Daily mean streamflow

DAILY

MEAN STREA

MFLO

W,

IN CUBIC FEET PER SECOND

90,000

60,000

30,000

0

1999 2000 2001

WATER YEAR

Figure 2. Surface water used for irrigation accounted for 98 percent of the average 6,452 million gallons per day of water used in the basin.

Figure 3. Flow of the Yellowstone River at Billings, Montana, water years 1999–2001. 

Streamflows in the basin were above average in water year 1999 but were less than

average in 2000 and 2001.

The Yellowstone River Basin 

encompasses four ecoregions (Omernik, 

1987: Northwestern Great Plains, 

Wyoming Basin, Middle Rockies, and 

Montana Valley and Foothill Prairies). 

Land cover throughout most of the basin 

is grass and shrubland in the Northwestern Great Plains and Wyoming Basin 

ecoregions (fig. 1). Coniferous forests 

and alpine areas in the Middle Rockies ecoregion cover about 20 percent of 

the basin, and land within Yellowstone 

National Park represents less than 5 percent of the total basin area. A small part 

of the basin is in the Montana Valley 

and Foothill Prairies ecoregion. Average 

annual precipitation ranges from about 6 

inches in the driest parts of the Wyoming Basin to almost 60 inches in the 

wettest parts of the Middle Rockies (Zelt 

and others, 1999).

Surface-Water 

Resources

The Yellowstone River is one of the 

longest free-flowing rivers remaining in 

the continental United States. Irrigation diversion dams can be found in the 

middle and lower sections of the river, 

but there are no major impoundments on 

the main stem. The Yellowstone River 

changes from a cold, clear, mountain 

river at the headwaters to a warmer, 

more turbid river downstream on the 

plains.

Major tributaries to the Yellowstone River include the Clarks Fork 

Yellowstone River, Bighorn River, 

Tongue River, and Powder River. The 

tributaries can be divided into three 

categories: mountain, basin, and plains 

streams. The ecoregion is an important 

factor in classification of the hydrologic 

characteristics of the tributaries. Soda 

Butte Creek and the upper reaches of the 

Tongue River (mountain streams) are 

part of the Middle Rockies ecoregion. 

Drainage area of the mountain streams 

is relatively small, and streamflow is 

dominated by the melting of the annual 

snowpack. The Clarks Fork Yellowstone River and Bighorn River (basin 

streams) are part of the Wyoming Basin 

stored, and cold, clear water is released 

below the dams.

Most water used in the basin is surface water withdrawn to irrigate fields 

located primarily in the river valleys and 

nearby areas (fig. 2). The forested mountains are the source of water for most 

perennial streams, and the winter snowpack in the mountains strongly influences streamflow throughout the year. 

The mountain streams are dominated by 

a single annual snowmelt peak of moderate duration during late spring or early 

summer, with little variability in daily 

flows throughout the year. Other streams 

originate in the plains. Many of these 

streams are intermittent or ephemeral, 

and sporadic higher flows are the result 

of local snowmelt or intense rainstorms. 

Flow during dry periods originates from 

ground water.

A reduced snowpack and drought 

caused below-average streamflow during 

much of the sample-collection period 

(fig. 3). Annual mean streamflow at 

some sampling sites in 2001 was the 

ecoregion. Drainage area is large, and 

the flow from these streams contributes 

substantially in total flow volume and in 

per unit area to the Yellowstone River. 

The Powder River and Little Powder 

River (plains streams) are predominantly 

in the Northwestern Great Plains

ecoregion. The flow cycle of plains 

streams is affected more by local and 

regional rain events than are the mountain streams. Plains streams also contribute less flow to the Yellowstone River 

per unit area than mountain streams.

 The Bighorn River is the largest tributary to the Yellowstone River 

and represents about 32 percent of the 

basin. Storage reservoirs with capacities 

greater than 600,000 acre-feet, such as 

Bighorn Lake and Boysen Reservoir, are 

located on the Bighorn River or its tributaries. Smaller reservoirs are located 

on the Tongue River; the Clarks Fork 

and Powder River are free-flowing. The 

reservoirs are important from a waterquality perspective because warm, turbid 

water flowing into the reservoirs is 

4 Water Quality in the Yellowstone River Basin, Wyoming, Montana, and North Dakota, 1999–2001
Additional Information

For additional information about 

the environmental setting and 

stratification for site selection in 

the NAWQA study of the Yellowstone River Basin, see Zelt and 

others (1999) or http://wy.water.

usgs.gov/YELL/htms/yellpubs.htm.

lowest on record. At other sites, 2001 

streamflow was the third or fourth lowest on record. Periods of low streamflow, 

such as during drought conditions, are 

characterized by large contributions of 

ground water, resulting in less dilution 

by runoff and larger concentrations of 

some dissolved constituents (p. 13).

Ground-Water Resources

The primary aquifers in the structural basins (for example, the Bighorn 

Basin in fig. 1) are unconsolidated 

deposits of Quaternary age and rocks of 

lower Tertiary, Mesozoic, and Paleozoic 

age. Rural residents often depend on 

shallow wells (less than 500 feet) that 

are completed in aquifers in Quaternary 

unconsolidated deposits or lower Tertiary consolidated sedimentary rocks.

The Quaternary unconsolidated 

deposits, primarily composed of sand 

and gravel interbedded with finer 

grained silt and clay, are limited in 

extent and occur mostly as alluvium or 

terrace deposits adjacent to and above 

narrow valleys along streams in the 

Yellowstone River Basin. In contrast, 

the lower Tertiary aquifers are widespread and primarily are composed of 

sandstone beds interbedded with finegrained rocks such as shale, claystone, 

mudstone, or siltstone. The areal extent 

of Quaternary unconsolidated-deposit 

aquifers (Quaternary aquifers) coincides with much of the rural population 

and irrigated cropland, making these 

aquifers particularly susceptible to the 

effects from human activities at the land 

surface.

Biological Resources

Cold-water fishes, including trout, 

whitefish, and sculpin, dominate the fish 

community of streams in the mountains 

and foothills of the basin. The Yellowstone cutthroat trout is the only native 

trout in the basin (Behnke, 1992) and is 

one of about six fish species in the Yellowstone River Basin of special concern 

in the State of Montana. Other coldboulders and cobbles in the upper 

reaches to predominantly gravel and 

finer material in the lower reaches.

Water-Quality Issues

The quality of surface water and 

ground water in the basin is affected by 

natural factors and nonpoint source and 

point-source contaminants associated 

with human development. For example, 

concentrations of trace elements (such 

as arsenic) and major ions (such as 

calcium and sulfate) in surface water and 

ground water are influenced by geologic 

factors, as are concentrations of suspended sediment and total phosphorus 

in surface water. Current water-quality 

conditions also reflect human influences, 

as indicated by the presence of pesticide

compounds in surface water, ground 

water, bed sediment, and fish tissue. 

Human and animal activities influence 

concentrations of bacteria, nutrients, 

suspended sediment, and other chemical 

and physical characteristics. Discharge 

of saline ground water from large-scale 

coalbed methane production areas in 

the Powder River Basin of Wyoming 

potentially affects stream-water quality. Habitat characteristics also are of 

interest; for example, the large floods on 

the Yellowstone River during 1996 and 

1997 prompted the State of Montana 

to assess the long-term effects of bank 

stabilization projects on the upper river 

(Governor’s Upper Yellowstone River 

Task Force, 2001). 

water native fishes commonly found in 

the basin include mountain whitefish 

and mottled sculpin (Baxter and Stone, 

1995; Brown, 1971). Rainbow, brown, 

and brook trout are all introduced species. Native warm-water game fish such 

as channel catfish and sauger occur in 

many of the streams in the plains (Patton, 1997; and Hubert, 1993). Fish species richness in the Yellowstone River 

and other streams in the basin generally 

increases downstream, from the mountainous cold-water streams to the warmwater plains streams.

White and Bramblett (1993) 

described three zones of fish communities in the Yellowstone River. The upper 

one-third of the Yellowstone River, 

from the headwaters downstream to just 

upstream from the mouth of the Clarks 

Fork, is a cold-water zone inhabited by 

16 fish species representing 6 families. 

The transition zone of the Yellowstone 

River extends downstream from Billings 

and to the mouth of the Bighorn River; 

30 fish species representing

7 families are resident. The lower Yellowstone River contains a warm-water 

fish community, including the only 

federally listed endangered species in 

the basin, the pallid sturgeon. Other fish 

species of the warm-water zone of the 

Yellowstone River include paddlefish, 

several species of sucker, and various 

species of native and introduced minnows and game fish, totaling 49 species 

and 15 families.

Aquatic invertebrates (insects, 

worms, snails, crayfish, and mussels), 

algae, and substrate also follow a gradient from mountains to plains. In the 

Yellowstone River, most invertebrate 

species occupy only one or two zones, 

but a few species of mayfly, stonefly, 

and caddisfly larvae are found throughout the length of the Yellowstone River 

(Newell, 1977). Few species of mussels 

are found in Montana, but indigenous 

populations are largely intact (Gangloff 

and Gustafson, 2000). An exotic species, 

the New Zealand mudsnail, has invaded 

Yellowstone National Park and has the 

potential to substantially affect aquatic 

ecosystems because of their high densities (Richards, 2002). The bed substrate 

of the Yellowstone River changes from 

Introduction 5
Figure 4. Dissolved solids are lower in mountain streams than in basin or 

plains streams. 

0

500

1,000

1,500

2,000

2,500

3,000

Soda Butte Creek

MOUNTAIN

STREAMS

BASIN

STREAMS

PLAINS

STREAMS

YELLOWSTONE

RIVER

Yellowstone River

at Corwin Springs

Clarks Fork

Yellowstone RiverYellowstone River

at Billings

Bighorn River

Yellowstone River

at Forsyth

Yellowstone River

near Sidney

Tongue River

Little Powder River

Powder Rive

M

r

EDIAN C

ONCENT

R

ATION

OF DIS

S

OLVED-S

OLID

S, IN

MILLIG

R

A

M

S PER LITER

Figure 5. Ground water discharged from 

coalbed methane development in the 

Powder River Basin commonly is stored in 

surface impoundments (photograph by

Jon P. Mason, U.S. Geological Survey).

Major Findings

Natural factors affect 

surface and groundwater chemistry

The diverse geology and climate 

of the Yellowstone River Basin are 

important factors affecting surface- and 

ground-water chemistry, including concentrations of dissolved solids, radon, 

nutrients, and trace elements. Throughout this report, standards and guidelines 

from various agencies and sources such 

as the U.S. Environmental Protection 

Agency (USEPA) (2002) drinkingwater standards are provided as a basis 

for comparison, but are not intended in a 

regulatory sense.

Mountain streams generally 

are dilute, whereas naturally 

occurring dissolved solids 

in basin and plains streams 

commonly exceed the Federal 

drinking-water guideline

Dissolved minerals in mountain 

streams, such as Soda Butte Creek in 

Yellowstone National Park and the 

Tongue River near Sheridan, Wyo., are 

dominated by calcium and bicarbonate. 

Median concentrations of dissolved solids for these streams are low (less than 

140 mg/L [milligrams per liter]) (fig. 4). 

During periods of snowmelt runoff in 

late spring, concentrations of dissolved 

solids are as low as 40 mg/L because of 

dilution by the meltwater.

In contrast to mountain streams, 

more than 95 percent of samples from 

the plains streams—the Little Powder 

and Powder Rivers—exceeded the 

USEPA secondary drinking-water guideline for dissolved solids of 500 mg/L. 

Secondary drinking-water guidelines 

are not enforceable but are intended as 

guides to esthetic values, such as taste 

and odor. Sodium and sulfate generally 

dominate the major ions of the Little 

Powder River and the Powder River; 

chloride concentrations are substantially 

higher in these streams than in mountain 

streams. Evaporative salts that commonly accumulate on the soil surface in 

the plains are flushed to streams during 

runoff of precipitation.

Dissolved-solids concentrations 

in basin streams and in the main stem 

of the Yellowstone River are intermediate between those of mountain and 

plains streams. Median concentrations 

of dissolved solids on the Yellowstone 

River increased from 152 mg/L near its 

mountainous headwaters to 452 mg/L at 

the farthest downstream site.

Land-use practices also

contribute dissolved solids to 

streams

Although natural factors are 

important, land-use practices, such as 

irrigation and oil and gas development, 

also contribute dissolved solids in the 

Yellowstone River Basin (LindnerLunsford and others, 1992). Effects 

of coalbed methane development on 

surface-water quality in the Tongue and 

Powder River Basins (fig. 5), which 

began in the late 1990s, are unclear. 

Data collected in these basins under the 

NAWQA Program prior to development 

may serve as an important baseline for 

assessing possible future water-quality 

effects.

Ground-water chemistry in the 

Quaternary and lower Tertiary 

aquifers is naturally variable 

and generally high in mineral 

content

Calcium, sodium, bicarbonate, and 

sulfate were the predominant major ions 

in water from the Quaternary aquifers. 

In the lower Tertiary aquifers, sodium, 

6 Water Quality in the Yellowstone River Basin, Wyoming, Montana, and North Dakota, 1999–2001
Concentrations of dissolved 

solids in both aquifers sampled in 

the Yellowstone River Basin were 

higher than in most shallow wells 

sampled elsewhere in the Nation. 

The median concentrations of 

dissolved solids of 956 mg/L for 

samples from the Quaternary 

aquifers and 1,302 mg/L for 

samples from the lower Tertiary 

aquifers were much higher than 

the median of 280 mg/L from 

2,391 domestic wells sampled 

nationally as part of the NAWQA 

Program from 1991 to 2001.

Water from study unit aquifers was more mineralized 

than water from other aquifers in the Nation

50

500

100

1,000

10,000

DISSOLVED-SOLIDS

CONCENTRATION, IN

MILLIGRA

MS PER LITER

YELLOWSTONE

RIVER BASIN

Quaternary

aquifers

Lower

Tertiary

aquifers

NAWQA

domestic wells

(many aquifers)

25

29 29

2,391 90th percentile

Number of samples

Percentile–Percentage of analyses equal

to or less than the indicated values

EXPLANATION

10th percentile

U.S. Environmental Protection Agency

secondary drinking-water guideline

75th percentile

25th percentile

Median (50th percentile)

5,000

bicarbonate, and sulfate were the most 

common major ions. Water in both 

aquifers with high concentrations of 

dissolved solids often was dominated by 

sodium and bicarbonate, particularly in 

the lower Tertiary aquifers where natural 

geochemical processes, such as cation 

exchange and bacterially mediated sulfate reduction, are important.

Concentrations of dissolved solids 

in water samples from the Quaternary 

aquifers ranged from 128 to

24,300 mg/L, with a median of

956 mg/L. Waters from the lower 

Tertiary aquifers generally were more 

mineralized, ranging from 352 to

5,800 mg/L, with a median of

1,302 mg/L.

Concentrations of dissolved solids 

in both aquifers frequently exceeded 

the USEPA secondary drinking-water 

guideline of 500 mg/L. The guideline 

was exceeded in 18 of 25 wells in the 

Quaternary aquifers and 27 of 29 wells 

in the lower Tertiary aquifers. Despite 

elevated concentrations, both of these 

aquifers are commonly used for domestic supplies. Many residents treat their 

well water to reduce the dissolved solids 

and improve the overall water quality.

Although natural factors control 

mineral content, cropland practices such 

as irrigation also are likely to contribute dissolved solids to ground water 

underlying the Bighorn Basin. The 

water table generally is shallow in both 

aquifers in this part of the Yellowstone 

River Basin, especially in the Quaternary aquifers. Salts from irrigation water 

can accumulate in agricultural soils and 

then be transported to aquifers following 

subsequent rainfall or irrigation.

Coliform bacteria concentrations exceeded 

Federal guidelines frequently in streams, but 

rarely in ground water

Coliform bacteria, including total 

coliform, fecal coliform, and Escherichia coli (E. coli), are commonly used 

to assess the sanitary quality of water 

because their presence can indicate contamination by fecal material. Although 

coliform bacteria do not necessarily 

cause illness, large concentrations of 

coliform bacteria can indicate the presence of other pathogens that cause the 

waterborne diseases gastroenteritis and 

bacillary dysentery, typhoid fever, and 

cholera (Myers and Sylvester, 1997). 

The criteria for evaluating concentrations of E. coli vary with intended use, 

ranging from designated beaches to 

infrequent full-body contact recreation 

(U.S. Environmental Protection Agency, 

1986).

Recommended Federal limits 

for recreational contact were 

frequently exceeded during 

special coliform-bacteria study 

of streams

Fecal coliform concentrations 

exceeded USEPA’s single-sample 

recommended limit of 400 col/100 mL 

(colonies per 100 milliliters) for primary 

contact recreation at 37 of 100 stream 

sites in the Wind River, Bighorn River, 

and Goose Creek (Sheridan area) Basins 

in Wyoming. Similarly, 38 percent of the 

samples contained E. coli concentrations 

greater than USEPA’s single-sample 

recommended limit of 298 col/100 mL 

for moderate use, full-body contact 

Major Findings 7
What are coliform bacteria?

Coliform bacteria belong to the Enterobacteriaceae family of bacteria. The total coliform 

group includes bacteria that are found in the 

intestines of warm-blooded animals, as well 

as those found in soils, on vegetation, and in 

industrial waste. Fecal coliforms are a subgroup of the total coliforms that generally are from fecal sources, but at least 

one member of the fecal coliform group has been associated with industrial 

waste sources (U.S. Environmental Protection Agency, 1986). Escherichia coli

is a specific subgroup of the fecal coliform group that is a natural inhabitant in 

the gastrointestinal tract of warm-blooded animals. The presence of Escherichia coli in recreational waters is direct evidence that fecal contamination 

from humans or other warm-blooded animals has occurred (Dufour, 1984).

Total coliform

Fecal coliform

Escherichia coli

0

100

200

300

400

500

600

MEDIAN CONCENTRATION, IN

COLONIES PER 100 MILLILITERS

Fecal coliform

Escherichia

coli

Forested

Rangeland

Agricultural

Urban

Figure 6. Median concentrations of coliform bacteria were highest in urban and 

agricultural areas.

Figure 7. Median concentrations of coliform bacteria were highest in spring and summer.

0

20

40

60

80

100

JAN FEB MAR APR MAY JUNE JULY AUG SEPT OCT NOV DEC

MEDIAN CONCENTRATION,

IN COLONIES PER

100 MILLILITERS

Fecal coliform

Escherichia coli

recreation, and 25 percent of the E. coli

concentrations exceeded the singlesample recommended limit for infrequent use, full-body contact recreation 

of 576 col/100 mL. Median concentrations of fecal coliform and E. coli were 

highest in urban and agricultural streams 

(fig. 6), where likely sources of coliform 

bacteria contamination include sewage treatment plants, agricultural and 

domestic animal waste, wildlife waste, 

and septic systems.

runoff was less frequent. Concentrations 

of fecal coliform and E. coli for these 

streams generally were less than recommended limits for recreational contact 

throughout the year. Fecal coliform 

concentrations in four samples from 

the Bighorn, Little Powder, and Powder 

Rivers exceeded the recommended limit 

of 400 col/100 mL. Of the 145 samples 

collected, concentrations of E. coli in 

11 samples exceeded the single-sample 

limit of 298 col/100 mL and concentrations in 6 samples exceeded the singlesample limit of 576 col/100 mL from 

the Clarks Fork, Bighorn, Little Powder, 

and Powder Rivers. Eighty percent of 

the samples that exceeded recommended 

limits for E. coli were collected in the 

summer. Recreational use of these 

streams generally is infrequent; however, 

the human health risk to exposure is 

highest during the summer when contact 

with waters is most likely to occur.

Coliform-bacteria concentrations in ground water were low 

compared to Federal guidelines

Total-coliform bacteria were 

detected in samples from 3 of 28 rural 

wells in Wyoming and Montana, and 

these exceeded the USEPA drinkingwater standard of zero. No E. coli bacteria were detected in any well samples. 

Bacteria in ground water might not be 

a widespread issue in the basin, but 

the data indicate some contamination. 

Some domestic wells are not grouted 

and are, therefore, more susceptible to 

contamination from surface sources than 

the sealed monitoring wells used in this 

study. 

Additional Information

For additional information about 

the special coliform bacteria study, 

see Clark and Gamper (2003) or 

http://wy.water.usgs.gov/YELL/

htms/yellpubs.htm.

Coliform bacteria varied

seasonally in streams

Median monthly concentrations of 

coliform bacteria generally increased 

in the late spring through June or July 

when peak concentrations occurred 

(fig. 7) in Soda Butte Creek, and the Yellowstone, Clarks Fork, Bighorn, Tongue, 

Little Powder, and Powder Rivers. The 

seasonal peak of more than

50 col/100 mL might result from 

increased runoff associated with lowland 

thunderstorms or snowmelt runoff. 

Concentrations of coliform bacteria 

declined in the late summer and fall, to 

less than 20 col/100 mL, when overland 

8 Water Quality in the Yellowstone River Basin, Wyoming, Montana, and North Dakota, 1999–2001
Radon concentrations in ground water were generally high 

compared to rest of Nation

Radon is a colorless, odorless 

radioactive gas that forms during the 

decay of natural uranium in rocks 

and soil. Concentrations of radon 

are naturally elevated in water in 

the Quaternary and lower Tertiary 

aquifers sampled in the Yellowstone River Basin. The water flows 

through volcanic rocks and some 

types of sedimentary and metamorphic rocks that contain enriched 

amounts of radium, a decay product 

of uranium. Concentrations of radon 

in 52 of 54 samples exceeded the 

USEPA proposed drinking-water standard of 300 pCi/L (picocuries per liter). 

One sample exceeded the USEPA proposed alternative drinking-water standard for radon of 4,000 pCi/L. About 75 percent of the ground-water samples collected in this study exceeded the national median of 470 pCi/L for radon in 2,078 

domestic wells sampled in NAWQA studies across the Nation. Relatively high concentrations of radon also have been 

noted in the Upper Colorado River Basin (Spahr and others, 2000) and the South Platte River Basin (Dennehy and others, 

1998). Radon is second only to cigarette smoking in causing lung cancer in the United States (Cothern and Smith, 1987).

25

29 2,078 2,078

100

500

300

1,000

5,000 4,000

TOTAL RADON, IN

PICOCURIES PER LITER

YELLOWSTONE

RIVER BASIN

EXPLANATION

Proposed U.S. Environmental Protection

Agency maximum contaminant level

Proposed alternative U.S. Environmental

Protection Agency maximum contaminant

level

Quaternary

u

deposit aquifers

nconsolidatedLowerTertiary

aquifers

NAWQA

domestic wells

(many aquifers)

90th percentile

Number of samples

Percentile—Percentage of analyses equal

to or less than the indicated values

10th percentile

75th percentile

25th percentile

Median (50th percentile)

Median concentrations of radon in water samples from Quaternary and Tertiary aquifers in the Yellowstone River Basin were higher than in other parts of the Nation.

Figure 8. Concentrations of total nitrogen 

were largest in streams with most rangeland.

0.1

1

10

0 50 100

RANGELAND AREA,

IN PERCENTAGE OF

STREAM DRAINAGE AREA

FLO

W-WEIGHTED AVERA

GE CONCENTRATION OF TOTAL NITRO

GEN,

IN MILLIGRA

MS PER LITER

Nutrient concentrations 

vary seasonally and in 

relation to land use

Concentrations of total nitrogen were largest in rangeland 

streams

Flow-weighted average concentrations (see inset on p. 10) of total nitrogen were 1.9 mg/L in the Little Powder 

River and 2.6 mg/L in the Powder River 

during 1999-2001, where the land 

cover in each basin is about 80 percent 

rangeland. The nitrogen in these streams 

is mostly organic nitrogen and is correlated with large particulate organic 

carbon concentrations. Concentrations 

of total nitrogen were less than 1.6 mg/L 

for other streams sampled, decreasing 

proportionally with the percentage of 

rangeland (fig. 8). The smallest concentrations of total nitrogen were measured 

in predominantly forested basins. In a 

nationwide model of contaminant transport by Smith and others (1997) (fig. 9), 

about 60 percent of the average total 

nitrogen yield in the Yellowstone River 

Basin was estimated to be from

nonagricultural sources. Nitrogen 

contributed from rangeland is under the 

nonagricultural source category in

figure 9.

Nitrate concentrations were largest in the Clarks Fork Yellowstone and 

Bighorn Rivers, both of which are basin 

streams that drain a mix of residential, 

agricultural, and undeveloped areas. 

The average concentration of nitrate 

at both sites was 0.38 mg/L (fig. 10). 

In contrast, average concentrations of 

nitrate for the mountain streams, Soda 

Butte Creek and Tongue River, were less 

than 0.08 mg/L, which is considered the 

upper limit of naturally occurring concentrations for other undeveloped areas 

of the Nation (Clark and others, 2000). 

Concentrations of nitrate in the Yellowstone River increased downstream 

from an average of about 0.08 mg/L at 

Corwin Springs to an average of greater 

than 0.3 mg/L near Sidney (fig. 1).

Nitrate concentrations in the samples from the main-stem Yellowstone 

River were largest during winter. The 

median concentration of nitrate at four 

sites on the Yellowstone River during 

Major Findings 9
Why are concentrations flow-weighted?

Nutrients and suspended sediment in streams are reported as flow-weighted 

average concentrations in this report. The flow-weighted average is calculated 

by first multiplying each sample concentration by its associated streamflow 

value, then dividing the sum of these products by the sum of the streamflows. 

The result is a concentration that is representative of the annual mass of the 

constituent transported by each stream. Flow-weighting concentrations is particularly important in a plains stream such as the Little Powder River, where 

daily flows are low for most of the year and stormflows usually are large and 

of short duration. For these streams, the flow-weighted average concentration 

likely is substantially larger than a most-probable concentration for any given 

day.

Figure 10. Concentrations of nitrate in mountain streams were less 

than concentrations for other developed areas. Concentrations of 

nitrate were largest in basin streams.

Figure 11. Nitrate concentrations in the Yellowstone River were largest during the winter 

and smallest during summer. Concentrations below reporting level are estimates.

Figure 9. Sources of nitrogen and phosphorus in the Yellowstone River Basin were 

predominantly nonagricultural, as estimated from nationwide analysis using the 

SPARROW model (Smith and others, 1997).

MONTH

OCT NOV DEC JAN FEB MAR APR MAY JUNE JULY AUG SEPT

0

0.1

0.2

0.3

0.4

0.5

0.6

Reporting level

CONCENTRATION OF

DISSOLVED NITRATE, IN

MILLIGRA

MS PER LITER

EXPLANATION

90th percentile

10th percentile

Median

(50th percentile)

0

10

20

30

40

50

60

70

NITROGEN PHOSPHORUS

AVERA

GE PROPORTION OF TOTAL

NUTRIENT YIELD, IN PERCENT

Point

EXPLANATION

Atmosphere

Nonagricultural (includes rangeland)

Livestock

Fertilizer

Soda Butte Creek

MOUNTAIN

STREAMS

BASIN

STREAMS

PLAINS

STREAMS

YELLOWSTONE

RIVER

Yellowstone River

at Corwin Springs

Clarks Fork

Yellowstone RiverYellowstone River

at Billings

Bighorn River

Yellowstone River

at Forsyth

Yellowstone River

near Sidney

Tongue River

Little Powder River

Powder Rive

F

r

LO

W-WEIGHTED

AVER

A

GE

C

ONCENT

R

ATION OF NIT

R

ATE,

IN MILLIG

R

A

M

S PER LITER

0

0.1

0.2

0.3

0.4

Undeveloped

areas

January was 0.38 mg/L (fig. 11). Median 

concentrations in the Yellowstone River 

were less than the minimum reporting 

level during July and August. Lower 

streamflow during winter results in less 

dilution of nitrate-rich ground water discharging to the stream. Uptake of nitrate 

by algae—an important process during 

summer that reduces concentrations in 

stream water—is minimal during winter 

when solar inputs are minimal and water 

temperatures are near freezing.

Natural sources contribute 

phosphorus and suspended 

sediment to streams

Flow-weighted average concentrations of phosphorus at three of four sampling sites on the Yellowstone River and 

in four tributary streams exceeded the 

USEPA goal of 0.1 mg/L for minimizing 

nuisance plant growth. Average concentrations of total phosphorus ranged 

from 0.2 mg/L to 2.1 mg/L for predominantly (50 percent or greater) rangeland 

streams.

Concentrations of phosphorus 

in soils and sediments of the Western 

United States are large relative to those 

in the Eastern United States (Shacklette 

and Boerngen, 1984) because phosphorus occurs naturally in the igneous 

10 Water Quality in the Yellowstone River Basin, Wyoming, Montana, and North Dakota, 1999–2001
Geothermal sources contribute nutrients and trace elements to the Yellowstone River

The flow-weighted average concentration of ammonia as nitrogen (hereinafter, ammonia) of 0.04 mg/L in the Yellowstone 

River at Corwin Springs, near the headwaters, was about twice as large as the median flow-weighted average concentrations in streams in other undeveloped areas of the Nation (graph A). Concentrations of ammonia in streams in undeveloped basins typically are closer to a background concentration of about 0.02 mg/L (Clark and others, 2000). One possible 

source of the large concentrations of ammonia at the Corwin Springs site is leaching of organic-rich sedimentary rocks 

by the high-temperature waters (D. Kirk Nordstrom, USGS, written commun., 2000; Love and Good, 1970). The largest concentrations in the Yellowstone River at Corwin Springs (as high as 0.23 mg/L) occur in the fall and winter months 

when inputs from geothermal sources are less diluted by surface runoff. Ammonia is common in many geothermal waters 

of Yellowstone National Park, where concentrations greater than 600 mg/L have been measured in some springs (Ball and 

others, 1998, p. 23).

Median concentrations of 

dissolved arsenic in samples 

from the Yellowstone 

River at Corwin Springs 

and at Billings exceeded 

the USEPA drinking-water 

standard of 10 micrograms 

per liter (graph B), probably 

because of the natural occurrence of arsenic in geothermal waters (Hem, 1985). 

In streams in and around 

Yellowstone National Park, 

arsenic remains in solution 

(Nimick and others, 1998). 

Downstream decreases in 

the concentration of arsenic—from Corwin Springs 

to Sidney—probably result 

from increased dilution by 

tributary inflows.

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Figure 12. Runoff from rainstorms transports high concentrations of sediment in 

plains streams such as the Little Powder 

River (photograph by Ronald B. Zelt, U.S. 

Geological Survey).

and marine sedimentary rocks that are 

prevalent. Phosphorus tends to attach to 

soil sediment particles so that the transport of these particles in suspension in 

streams typically causes concentrations 

of total phosphorus to increase with 

increasing concentrations of suspended 

sediment (U.S. Geological Survey, 

1999). In the Yellowstone River Basin, 

nonagricultural sources of phosphorus 

(such as suspended sediment, although 

sediment concentrations might be 

affected indirectly by agriculture) were 

estimated to have contributed about 

65 percent of the total phosphorus yield; 

human activities, such as fertilizer applications and raising stock, also contribute 

phosphorus to streams (fig. 9).

The sparse vegetative cover and 

erodible soils in the basins and plains 

areas contribute to larger suspendedsediment concentrations in basin and 

plains streams than in mountain streams 

(fig. 12). Flow-weighted average 

concentrations of suspended sediment 

generally were proportional to the area 

of rangeland in the stream drainage 

(fig. 13), and were correlated with surficial Tertiary-age sedimentary rocks that 

are susceptible to erosion.

Sediment yields (total amount 

contributed per unit area) generally were 

large from major tributary basins, such 

as the Clarks Fork Yellowstone, Bighorn, and Powder Rivers (fig. 14). The 

maximum annual sediment yield was 

Major Findings 11
Flow-weighted average concentrations of total phosphorus at sites on the Little Powder River, Powder River, and 

Clarks Fork Yellowstone River ranked in the upper 11 percent of their respective land-use categories and the upper 

13 percent of all samples collected during 1993–2001 in NAWQA studies across the Nation. Land in the Little Powder 

River and Powder River Basins is primarily undeveloped rangeland, whereas the Clarks Fork Yellowstone River Basin 

includes a variety of land uses, such as residential, agricultural, and undeveloped areas. The high concentrations of phosphorus in soils and high suspended-sediment concentrations in the streams are the primary causes of the large concentrations of total phosphorus in samples from undeveloped areas. In areas of mixed land use, human-related sources are 

important. For example, Smith and others (1997) estimated that fertilizer and manure contributed 45 percent of

phosphorus to the Clarks Fork Yellowstone River.

Streams in Undeveloped Areas Streams in Mixed Land Use Areas

Phosphorus concentrations in streams in undeveloped and 

mixed land-use areas are among the largest in the Nation

Powder River

Yellowstone River at Billings Clarks Fork

Yellowstone River

Yellowstone River at Sidney

Bighorn River

Yellowstone River at Forsyth

Little Powder

River

Tongue River

Soda Butte Creek

Yellowstone River

at Corwin Springs

Mean annual concentration

of total phosphorus, in

milligrams per liter

Less than 0.05

0.05 to 0.3

Greater than 0.3

Phosphorus input, in pounds per acre

Less than 2

2 to 5

Greater than 5

EXPLANATION

Figure 14. Suspended-sediment yields were largest in basin and plains streams 

that have little vegetation and soils that are susceptible to erosion.

Soda Butte Creek Insufficient data

MOUNTAIN

STREAMS

BASIN

STREAMS

PLAINS

STREAMS

YELLOWSTONE

RIVER

Yellowstone River

at Corwin Springs

Clarks Fork

Yellowstone RiverYellowstone River

at Billings

Bighorn River

Yellowstone River

at Forsyth

Yellowstone River

near Sidney

Tongue River

Little Powder River

Powder River

ANNUAL SUSPENDED-SEDIMENT

YIELD, IN TONS PER SQUARE

MILE 100

0

200

300

400

500

Figure 13. Suspended-sediment concentrations generally increase with the percentage of rangeland.

10,000

1,000

100

10

0 20 40 60 80 100

RANGELAND AREA,

IN PERCENTAGE OF

STREAM DRAINAGE AREA

FLO

W-WEIGHTED AVERA

GE

CONCENTRATION OF

SUSPENDED SEDIMENT,

IN MILLIGRA

MS PER LITER

12 Water Quality in the Yellowstone River Basin, Wyoming, Montana, and North Dakota, 1999–2001
Drought is an important factor in determining water-quality characteristics

Suspended-sediment yields were 

larger in basin and plains streams 

during 1999 than during the drought 

years 2000-2001 (graph A). The 

erodible soils of the basins and plains 

areas are transported in runoff to 

streams during storms. Less runoff 

during drought periods results in less 

sediment being delivered to streams.

In contrast, flow-weighted concentrations of nitrate in the basin and plains 

streams were smaller during 1999 

than during 2000–2001 (graph B). 

The larger nitrate concentrations 

during the drought years were caused 

in part by less dilution of nitrate-rich 

ground water discharging to the streams. Miller (1999) described substantial increases in concentrations of dissolved constituents in the upper reaches of the Yellowstone River during a previous drought. Total nitrogen concentrations in these 

streams decreased or remained the same between the two periods.

0

0.1

0.2

0.3

0.4

0.5

BASIN AND PLAINS

STREAMS

MEDIAN FLO

W-WEIGHTED AVERA

GE NITRATE

CONCENTRATION, IN MILLIGRA

MS PER LITER

MEDIAN ANNUAL SUSPENDED-SEDIMENT

YIELD, IN TONS PER SQUARE MILE

YELLOWSTONE

RIVER

Water year 1999 Water year

1999

Water years

2000–01

Water years

2000–01

BASIN AND PLAINS

STREAMS

YELLOWSTONE

RIVER

0

100

200

300

400

500

600

700

800

A B

400 tons per square mile in the Clarks 

Fork Yellowstone River. Sediment yields 

did not vary much in the Yellowstone 

River from the upstream segments to the 

downstream segment at Sidney.

Large reservoirs on the Bighorn River 

store much of the sediment, thus reducing sediment transport to the Yellowstone River.

Concentrations of nitrate 

in ground water generally 

were low, but occasionally 

exceeded the Federal drinkingwater standard

Concentrations of nitrate in 32 percent of the wells in Quaternary aquifers 

and 17 percent of the wells in the lower 

Tertiary aquifers exceeded 2 mg/L, 

which generally indicates ground-water 

contamination from human sources 

(Mueller and Helsel, 1996). Median 

concentrations of nitrate were about 

0.2 mg/L for the Quaternary aquifers 

and about 0.08 mg/L for the lower Tertiary aquifers.

Concentrations of nitrate in 

8 percent of samples collected from 

Quaternary aquifers and 3 percent from 

the lower Tertiary aquifers exceeded 

the USEPA drinking-water standard of 

10 mg/L. Drinking water with concentrations greater than this standard can 

result in insufficient levels of oxygen 

in the blood of infants and other health 

problems (Centers for Disease Control 

and Prevention, 1996).

Concentrations of nitrate in ground 

water are, in part, related to the percentage of different land uses surrounding the wells. Nitrate concentrations 

in Quaternary aquifers increased with 

the percentage of cropland and other 

agricultural land; nitrate concentrations 

decreased as the percentage of rangeland 

and riparian land increased. A similar 

relation was observed in samples from 

the lower Tertiary aquifers—nitrate concentrations increased with the percentage of cropland overlying the aquifer. 

Patterns observed in this study are typical of those observed in other groundwater systems across the Nation, where 

nitrate concentrations commonly are 

higher in shallow ground water underlying agricultural areas than in shallow 

ground water underlying other land-use 

areas (Mueller and Helsel, 1996).

Pesticides were detected 

frequently in streams, 

ground water, and fish 

tissue, but at low concentrations

Pesticides were frequently 

detected in streams

At least one pesticide compound 

was detected in 87 percent of 136 

water samples collected at three mixed 

land-use sites on the Yellowstone River 

and two mixed land-use sites on the 

Clarks Fork Yellowstone and Bighorn 

Rivers. Of the 47 different pesticide 

compounds analyzed, 20 were detected, 

including 14 herbicides, 5 insecticides, 

and 1 breakdown product (fig. 15). 

Atrazine, the most frequently detected 

herbicide, was identified in 75 percent 

of the samples and accounted for the 

highest concentration of any pesticide 

measured in the study—0.328 μg/L 

(micrograms per liter). Frequent detections of atrazine in streams may result 

Major Findings 13
BREAKDO

WN

PRODUCT

INSECTICIDES HERBICIDES

Malathion

Chlorpyrifos

Carbofuran

Carbaryl

Dieldrin

Terbufos

Deethylatrazine

Pesticide detected

EXPLANATION

Pesticide concentration less than or equal to 0.01 microgram per liter

0 10 20 30 40 50 60 70 80 90 100 0 10 20 30 40 0 10 20 30 40

FREQUENCY OF DETECTIONS, IN PERCENT

Rivers and streams

Quaternary

aquifers

Lower

Tertiary

aquifers

Atrazine

Metolachlor

Triallate

Prometon

Cyanazine

EPTC

DCPA

Simazine

Benfluralin

Alachlor

Acetochlor

Ethalfluralin

Tebuthiuron

Trifluralin

Figure 15. Herbicides were detected more often than insecticides in streams and aquifers.

from its moderate to high mobility in 

soils and its extensive use; it is the 10th 

most heavily used pesticide in the basin 

of all pesticides analyzed for this study. 

Atrazine also can move long distances 

through atmospheric transport (Goolsby 

and others, 1995). Triallate, the most 

heavily applied pesticide in the basin of 

the pesticides that were analyzed (U.S. 

Department of Commerce, 1995), was 

detected in 38 percent of the stream 

samples. Insecticides were detected less 

frequently than most herbicides. Chlorpyrifos, the most frequently detected 

insecticide, was identified in 5 percent of 

the samples. Organophosphate insecticides tend to have low application rates 

and break down rapidly in the environment (Nowell and others, 1999).

Pesticides seldom occurred alone in 

streams. Mixtures of two or more compounds were detected in 102 samples 

(75 percent). About 33 percent of the 

stream samples contained four or more 

pesticide compounds. One sample from 

the Bighorn River contained a mixture 

of 10 different compounds—8 herbicides, 1 insecticide, and 1 breakdown 

product. Multiple pesticide compounds 

were detected in individual samples 

throughout the year but varied 

seasonally in streams. The seasonality reflected mainly the timing and 

amount of chemical use and the 

frequency and magnitude of runoff 

from precipitation and irrigation. For 

example, 71 percent of the samples 

containing mixtures of four or more 

pesticides were collected during May 

to September following pesticide 

applications. Detections of one or 

more pesticide compounds during 

the winter months may indicate that 

ground water contributes some pesticides to streams because these compounds typically are not used in the 

winter. Possible risks to humans and 

aquatic life from pesticide compounds 

in the Yellowstone River Basin 

remain unclear because standards 

and guidelines for drinking water and 

aquatic life have not been established 

for many of the compounds and their 

breakdown products. Moreover, existing standards do not address exposure 

to mixtures of pesticides.

Pesticides were detected in 

both aquifers

Pesticides were detected in water 

from the Quaternary and lower Tertiary aquifers but were detected more 

frequently in samples collected from 

Quaternary aquifers (fig. 15). At least 

one pesticide compound was detected in 

14 of 25 wells in the Quaternary aquifers 

and in 4 of 29 wells in the lower Tertiary 

aquifers. Mixtures of two or more pesticides were detected in 11 wells in the 

Quaternary aquifers and in two wells in 

the lower Tertiary aquifers. The occurrences of such mixtures in the Yellowstone River Basin aquifers are typical 

of other aquifers sampled by NAWQA 

across the Nation (Gilliom, 2001).

Cropland overlies 22 percent of the 

Quaternary aquifers in the area studied. 

Application of water exceeding crop 

requirements can result in water-soluble 

pesticides being transported through 

soils to shallow aquifers (Barbash and 

Resek, 1996). The Quaternary aquifers 

typically are unconfined and the water 

table is shallow, making these aquifers 

vulnerable to surficial contaminants. 

The lower Tertiary aquifers are less 

vulnerable to contamination than the 

Quaternary aquifers because less area 

is overlain by irrigated cropland (only 

about 10 percent) and because of the 

hydrologic condition. The water table is 

deeper, and the aquifer consists of consolidated rocks that inhibit or reduce the 

flow of water and dissolved pesticides to 

these aquifers.

Herbicides were detected in 

ground water much more frequently 

than insecticides (fig. 15). Nine different herbicides and one insecticide were 

detected in samples from wells in the 

Quaternary aquifers; only two herbicides 

and no insecticides were detected in 

samples from wells in the lower Tertiary 

aquifers. Atrazine was the pesticide 

detected most frequently (29 percent) in 

the Quaternary aquifers. Dieldrin was 

the only insecticide detected in groundwater samples, occurring in only one 

well in the Quaternary aquifers. Most 

of the pesticides detected in ground 

water in both aquifers are commonly 

associated with agriculture. However, 

the second-most frequently detected 

pesticide, prometon, is commonly used 

14 Water Quality in the Yellowstone River Basin, Wyoming, Montana, and North Dakota, 1999–2001
Herbicide concentrations in surface water were low 

compared to National stream data

Concentrations of herbicides in samples from five mixed land-use stream sites in the Yellowstone River Basin were 

relatively low compared to samples from 42 stream sites draining mixed land-use settings across the Nation. Concentrations measured at Yellowstone River Basin sites ranked in the lowest 25 percent of concentrations measured nationwide 

and were similar to the ranking for sites in the adjacent States of Idaho and Utah. Concentrations of herbicides in samples 

from the five sites in the Yellowstone River Basin ranked 145th or lower when compared to 153 streams sites that drain 

agricultural, urban, or mixed land-use settings across the Nation. The low concentrations in this basin most likely reflect 

the low use of herbicides, particularly when compared to herbicide use in the Midwest and Eastern United States.

Herbicide concentrations in surface water were among 

the lowest in the Nation

20 Sum of herbicide concentrations–75th percentile, in micrograms

per liter

Streams with Mixed Land Use

Aquatic-life guidelines

Bold outline indicates exceedance of a guideline by one or more

herbicides. Number is percentage of samples that exceeded a

guideline within a 1-year period. Percentages less than 20 are

not labeled.

Highest 25 percent (greater than 1.070)

Middle 50 percent (0.093 to 1.070)

Lowest 25 percent (less than 0.093)

Urban areas

(shown only for

conterminous United States)

Herbicide use–in pounds per acre of agricultural land

Highest (greater than 0.406)

Medium (0.090 to 0.406)

Lowest (less than 0.090)

No reported use

Yellowstone

River Basin

EXPLANATION

for weed control along roads and other 

public areas and also is incorporated 

into asphalt used for road construction 

and repair. Prometon also is detected 

frequently in ground water throughout 

the United States (Squillace and others, 

2002).

Breakdown products of pesticides were present in streams 

and ground water

Deethylatrazine, a breakdown product of atrazine, was detected in about 40 

percent of all stream samples, and was 

present in all streams where pesticides 

were monitored. In wells in the Quaternary aquifers, deethylatrazine was 

detected more frequently than any other 

pesticide compound and at a slightly 

higher frequency (33 percent) than 

atrazine (29 percent). In lower Tertiary 

aquifers, deethylatrazine was detected in 

only one well.

Concentrations of pesticides 

and other organic compounds 

in fish tissue and bed sediment 

varied with land use

Organochlorine pesticides, such 

as the insecticides DDT, dieldrin, and 

chlordane, were detected in fish from 

several sites draining areas with mixed 

land uses. The compound detected most 

often in 22 fish-tissue samples was DDE 

(fig. 16). Another breakdown product of 

DDT, DDD, also was detected in about 

30 percent of the samples. Pesticides 

were not detected in fish-tissue samples 

from undeveloped areas, with the 

exception of those in the northwestern 

part of the basin (see sidebar on p. 17). 

Bed-sediment samples collected in 

conjunction with the fish-tissue samples 

generally did not contain detectable concentrations of pesticides. One exception 

was a bed-sediment sample from Goose 

Creek that contained DDT at a concentration of 2.2 micrograms per kilogram 

dry weight.

Polychlorinated biphenyls, more 

commonly known as PCBs, were 

detected in 3 of 22 fish-tissue samples. 

The highest concentration of total PCBs 

in fish tissue (190 micrograms per kilogram wet weight in common carp from 

Goose Creek near Sheridan) exceeded 

the New York State recommendation 

of 110 micrograms per kilogram dry 

weight for protection of piscivorous 

(fish-eating) wildlife (Newell and others, 

1987). The recommendation from New 

York is used here as a point of reference 

Major Findings 15
Fish-tissue samples from 6 of 10 sites draining undeveloped land in the Yellowstone River Basin contained no 

detectable concentrations of organochlorine insecticide compounds, such as DDE and chlordane. Those sites included 

rangeland sites and forested mountain sites. This finding is consistent with national findings. About 50 percent of 

165 sites in undeveloped areas sampled by NAWQA during 1992–2001 contained no detectable concentrations of pesticides (map A). Pesticide concentrations in fish from areas of mixed land uses in the Yellowstone River Basin were in the 

second-highest 56 percent on a national basis (map B). None of the concentrations of pesticides in fish tissue from the 

basin was in the highest 25 percent nationally nor did they exceed guidelines for the protection of fish-eating wildlife. 

Similarly, concentrations of organochlorine pesticides in bed sediment, PCBs in fish tissue and bed sediment, and semivolatile organic compounds in bed sediment generally were low in the basin, compared to national concentrations.

Concentrations of pesticide compounds in fish from the 

Yellowstone River Basin were low to moderate compared 

to the rest of the Nation

Sum of organochlorine

pesticide concentrations

A. Streams in Undeveloped Areas

Wildlife guidelines

Bold outline indicates exceedance of a guideline by one or more

organochlorine pesticides

Highest 25 percent

Second highest 56 percent

Lowest 19 percent (all with no

detections)

Historical organochlorine insecticide

use in agriculture–in pounds per acre

of agricultural land*

Highest (greater than 0.278)

Medium (0.095 to 0.278)

Lowest (less than 0.095)

No reported use

*Data available for conterminous United States only.

EXPLANATION

Yellowstone

River Basin

B. Streams with Mixed Land Use

Urban areas

(shown only for

conterminous United States)

Yellowstone

River Basin

Additional Information

For additional information about 

organic compounds in fish tissue 

and bed sediment of the Yellowstone River Basin, see Peterson 

and Boughton (2000).

because no National or State guidance 

is available for the basin. PCBs were 

not detected in any the bed-sediment 

samples from the basin.

Higher concentrations and more 

compounds were detected in fish tissue 

than in the bed-sediment samples from 

the Yellowstone River Basin, suggesting 

that fish are more sensitive indicators of 

organic contamination than bed sediment. The physical and chemical properties of the organochlorine pesticides 

and PCBs lead to their accumulation in 

sediment and tissue rather than water 

(Nowell and others, 1999).

Concentrations of semivolatile 

organic compounds in bed sediment 

generally were less than guidelines 

established by the Canadian Council of 

Ministers of the Environment (2000). 

The exceptions were two sites near 

urban areas of Billings and Sheridan that 

contained a broad suite of compounds, 

including polycyclic aromatic hydrocarbons (PAHs). Concentrations of 

benzo(a)pyrene, fluoranthene, and other 

PAHs in bed sediment were in the range 

of concentrations that poses possible 

adverse effects to aquatic life.

16 Water Quality in the Yellowstone River Basin, Wyoming, Montana, and North Dakota, 1999–2001
What guidelines are available for evaluating bed sediment?

The guidelines for evaluating organic compounds and trace elements in bed sediment from the Canadian Council of Ministers of the Environment (CCME) (2000) are used in this report because no Federal or State regulations from the states in 

the study area are available. The CCME defined an interim sediment-quality guideline (ISQG) and a probable effects level 

(PEL). Concentrations of contaminants in bed sediment below the ISQG are not likely to cause adverse effects to aquatic 

biota, whereas concentrations above the PEL often are associated with adverse effects to aquatic life. Concentrations 

between the ISQG and the PEL are in an intermediate range associated with possible effects to biota. 

The Environmental Legacy of DDT

General use of DDT in the United States was prohibited in 1972 because of concerns about its toxic effects to humans and 

wildlife and the environmental persistence and biomagnification of the compound. The presence of DDT in cutthroat trout 

collected in 1998 from the Yellowstone River near Fishing Bridge in Yellowstone National Park indicates this insecticide 

is persistent in the environment. Those fish, as well as cutthroat trout from a mountain stream north of the park, contained the parent DDT compound and breakdown products of DDT at concentrations that were among the highest (up to 

64.5 micrograms per kilogram) in the basin. A possible source of the DDT in the fish samples might be DDT sprayed in 

the northern part of Yellowstone Park in 1957 to control spruce budworm (Cope, 1961). Brown trout samples collected in 

1957 by Cope (1961) from the Yellowstone River at Corwin Springs (7 miles downstream from the park) contained about 

100 times more total DDT than a brown trout sample collected from the same site in 1998. The apparent attenuation of the 

DDT during the 41 years between samples likely results from breakdown, burial in sediment, and transport of the compound downstream.

Figure 16. Concentrations of DDT and its breakdown products, DDD and DDE, in fish tissue generally were higher at sites 

with mixed land use and those near Yellowstone National Park than in other undeveloped areas.

Yellowstone River at Billings

Bighorn River at Kane

Bighorn Lake at Highway 14A .

Shoshone River

Yellowstone River at Forsyth

Clarks Fork Yellowstone River

0

10

20

30

40

50

60

70

C

O

N

CEN

T

R

ATIO

N, IN

MIC

R

O

G

R

A

M

S

PER

KILO

G

R

A

M

WET

WEIGHT

Yellowstone River at Corwin Springs

Yellowstone River at lake outlet

West Fork Mill Creek

Wood River

Crow Creek

Little Bighorn River

Tongue River near Dayton

Crazy Woman Creek

Little Powder River

Soda Butte Creek

Goose Creek

Tongue River at State line

Yellowstone River near Sidney

Sage Creek

Arrow Creek

p,p'-DDE

DDT and products

Land use

p,p'-DDT

p,p'-DDD

o,p'-DDD

Undeveloped

Oil and gas

Agricultural

Mixed

Major Findings 17
Figure 17. Streams in mineralized areas, 

such as the Wood River in the Absaroka 

Range, often have high concentrations of 

trace elements in bed sediment 

(photograph by Gregory K. Boughton, 

U.S. Geological Survey).

Commonly detected volatile organic compounds 

in Quaternary aquifers 

are associated with

gasoline

Volatile organic compounds 

(VOCs)—including manufactured 

organic chemicals used in gasoline, fuel 

oils, lubricants, solvents, fumigants, 

pesticides, and sometimes as byproducts of chlorine disinfection (trihalomethanes)—were detected frequently 

in water samples collected from the 

Quaternary aquifers. At least one VOC 

was detected in 21 of 25 wells (about 

84 percent). Of the 85 VOCs analyzed, 

9 different compounds were detected, 

5 of which are commonly associated 

with gasoline. The VOC 1,2,4-trimethylbenzene was detected most frequently 

(18 of 25 wells) and at the highest concentrations. Other gasoline-associated 

hydrocarbons detected were benzene 

(9 wells), isopropylbenzene (2 wells), 

2-ethyltoluene (1 well), and p-isopropyltoluene (1 well). The other VOCs 

detected were solvents: carbon disulfide 

(4 wells), n-propylbenzene (1 well), 

tetrahydrofuran (1 well), and tetrachloroethene (1 well).

In contrast, one or more VOCs 

were detected in only 14 of 29 wells 

(48 percent) in the lower Tertiary 

aquifers. The VOCs detected in the 

lower Tertiary aquifers were different 

from those detected in the Quaternary 

aquifers—only two detections (benzene) were of gasoline compounds. 

Other VOCs detected were solvents or 

trihalomethanes: chloromethane (8 of 

29 wells), carbon disulfide (4 wells),

tetrahydrofuran (4 wells), trichloromethane (3 wells), tetrachloroethene

(1 well), and bromodichloromethane

(1 well).

Concentrations of VOCs in both 

aquifers were low, always below established USEPA drinking-water standards 

for these compounds.

Some trace-element concentrations in streams 

and bed sediment 

exceeded aquatic-life 

guidelines

Trace elements occur naturally in 

the environment, and many, such as copper and selenium, are required micronutrients for life (Sorenson, 1991). In 

excessive concentrations, however, trace 

elements can be toxic and can negatively 

affect growth, reproduction, and other 

biological functions.

Mineralized areas are located in the 

northwestern part of the basin, where 

concentrations of copper, lead, chromium, zinc, and other trace elements in 

bed sediment tended to be high (fig. 17). 

Concentrations of copper, arsenic, lead, 

and chromium in bed-sediment samples 

from the mineralized areas sometimes 

were within the range of concentrations 

that indicates possible adverse effects to 

aquatic life as defined by the Canadian 

Council of Ministers of the Environment 

(CCME) (2000).

Concentrations of copper in 

cutthroat trout and in bed sediment 

from Soda Butte Creek, a mineralized 

watershed, were among the highest 

from the basin. The concentrations of 

copper in bed sediment from Soda Butte 

Creek and other mineralized sites in 

the basin, as well as some of the mixed 

Ground water underlying 

low-density development 

generally is suitable for 

domestic use

The quality of shallow groundwater underlying low-density development outside of Sheridan and Lander, 

Wyo. and Red Lodge, Mont., generally 

is suitable for domestic use without 

treatment. Effects of human activities 

associated with residential development, such as septic systems; fertilizer 

and pesticide use on lawns, pastures, 

and gardens; manure from horses and 

pets; and increases in road construction 

and vehicular traffic were minimal at 

the time of sampling (2001). Pesticides 

and VOCs were detected infrequently in 

29 wells installed for this study (10 each 

in Lander and Sheridan and 9 in Red 

Lodge). Concentrations of pesticides 

and VOCs always were below applicable drinking-water standards. Concentrations of nitrate were all below the 

background concentration of 2 mg/L, 

indicating minimal effects from human 

activities. Total coliform bacteria were 

detected infrequently (in 3 wells), and 

E. coli were never detected. Traces of 

methylene blue active substances—

ingredients in laundry detergents—were 

detected in 11 wells, indicating possible 

aquifer contamination from septic-tank 

effluents.

Chlorofluorocarbon age-dating

indicated much of the water had 

recharged the shallow aquifers during 

the early 1990s or earlier. Chemical 

constituents in shallow ground water in 

2001 may, therefore, not yet reflect lowdensity development surrounding the 

Sheridan, Lander, and Red Lodge areas 

during the past decade. Continued monitoring is needed to determine effects on 

water quality from increasing residential 

development over time.

18 Water Quality in the Yellowstone River Basin, Wyoming, Montana, and North Dakota, 1999–2001
Additional Information

For additional information about 

trace elements in fish tissue and 

bed sediment, see Peterson and 

Boughton (2000). Trace elements 

in bed sediment also are discussed 

by Peterson and Zelt (1999) and 

Boughton (2001).

CRETACEOUS SEDIMENTARY ROCKS,

IN PERCENT OF STREAM BASIN

CONCENTRATION OF DISSOLVED

SELENIUM, IN MICRO

GRA

MS PER LITER

0 GREATER THAN 20

0

0.5

1.0

1.5

2.0

2.5

EXPLANATION

90th percentile

10th percentile

Median (50th percentile)

Figure 18. Selenium concentrations are 

larger from basins with more surface exposure of Cretaceous rocks.

land-use sites, were within the CCME 

intermediate range of possible adverse 

effects to aquatic life. The concentrations of copper from Soda Butte Creek, 

however, were below levels associated with adverse effects to biota in a 

previous study of Soda Butte Creek 

by Nimmo and others (1998). Sources 

of copper in the bed sediment of Soda 

Butte Creek include an upstream former 

mine-tailings impoundment. Concentrations of copper in water samples from 

Soda Butte Creek and other NAWQA 

sampling sites in the Yellowstone River 

Basin were less than the hardness-based 

criterion for the protection of aquatic 

life.

Concentrations of dissolved arsenic 

in stream samples were as large as 

42 μg/L in the Yellowstone River at 

Corwin Springs, where arsenic naturally occurs in geothermal waters. The 

median concentration of arsenic in the 

Yellowstone River at Corwin Springs 

was 21.0 μg/L; 78 percent of the arsenic 

concentrations at this site exceeded the 

USEPA drinking-water standard of

10 μg/L. Concentrations were lower, but 

still elevated, farther downstream at Billings, where the median was 10.5 μg/L 

(p. 11); 60 percent of the concentrations 

from the site at Billings exceeded the 

USEPA drinking-water standard. Human 

ingestion of arsenic in water can damage 

the skin and circulatory systems and 

may result in increased risk of cancer. 

The arsenic concentration in many of the 

bed-sediment samples was in the CCME 

intermediate range of concentrations 

that indicates possible adverse effects to 

aquatic biota. One bed-sediment sample, 

containing 41 micrograms per gram 

arsenic from the Yellowstone River at 

Corwin Springs, was in the CCME range 

of concentrations that indicates probable 

effects to aquatic biota (the arsenic PEL 

is 17 micrograms per gram). 

Concentrations of dissolved 

selenium in streams were as large as 

4.6 μg/L in the Powder River. The 

flow-weighted average concentration for 

water years 2000 and 2001 was

2.5 μg/L. Although these concentrations are less than the aquatic chronic 

criterion of 5 μg/L, concentrations of 

total recoverable selenium in water 

stone River were less than the USEPA 

criterion. The mean concentration of 

mercury in fish fillets from the Yellowstone River Basin ranked 5th highest 

among 20 NAWQA basins sampled 

across the Nation, but concentrations of 

total and methyl mercury in water and 

sediment were lower, comparatively 

(Brumbaugh and others, 2001). Mercury 

concentrations in fish samples were best 

correlated with methylmercury concentration in water samples, but chemical and physical processes associated 

with reservoirs also might be a factor 

influencing mercury concentrations in 

fish from the Yellowstone River Basin 

(Brumbaugh and others, 2001). Generally, less than 10 percent of the total 

mercury in bed-sediment samples from 

the Yellowstone River Basin was in the 

form of methylmercury, which is more 

toxic to biota than elemental mercury.

greater than 2 μg/L may produce adverse 

effects on some fish and wildlife (U.S. 

Department of Interior, 1998). Selenium 

may accumulate to toxic concentrations 

in the food chain when concentrations in 

the water are in the 0.5- to 3-μg/L range 

(Lemly, 1996). Compared to data for 

irrigation drainage studies (U.S. Department of the Interior, 1998), the concentration of selenium in many fish-liver 

samples from the basin was higher than 

the background range but lower than levels of concern for protection of fish and 

wildlife; the concentration of selenium 

in bed-sediment samples was within the 

background range and generally less 

than the levels of concern.

Selenium concentrations were 

larger in the Powder River and other 

streams in the basin draining a high 

proportion of Upper Cretaceous sedimentary rocks of marine origin, in which 

selenium occurs naturally, than in those 

streams that drain proportionally smaller 

areas of such rocks (fig. 18). For example, the median concentration of dissolved selenium was 1.3 μg/L in stream 

basins with greater than 20 percent Cretaceous sedimentary rocks, whereas the 

median was only 0.7 μg/L in basins with 

no such rock. Previous investigations 

have documented mobility of selenium 

in alkaline soils in the arid regions of the 

Western United States. Concentrations 

of dissolved selenium also are larger in 

streams draining irrigated lands with 

those characteristics (U.S. Department 

of Interior, 1998).

Concentrations of mercury in 

edible portions of game fish reached a 

maximum of 0.676 microgram per gram 

(wet weight) in skinless fillets of walleye 

from Bighorn Lake. This concentration 

is in the range of concentrations used 

by the Montana Department of Public 

Health and Human Services (2003) to 

issue a fish-consumption advisory for 

Bighorn Lake. Concentrations of mercury in walleye from Bighorn Lake and 

its two major tributaries, the Bighorn 

River and the Shoshone River, exceeded 

the USEPA criterion of 0.3 milligram 

methylmercury per kilogram of fish 

(U.S. Environmental Protection Agency, 

2003). Concentrations of mercury in fish 

from the Tongue River and the YellowMajor Findings 19
1

10

PERIPHY

T

ON CHLO

R

OPHYLL- ,

IN MILLIG

R

A

M

S PER

S

QUA

RE METER

a

100

1,000

Yellowstone River near Livingston

Yellowstone River at Greycliff

Yellowstone River at Laurel

Yellowstone River at Billings

Yellowstone River at Custer

Yellowstone River at Forsyth

Yellowstone River at Miles City

Yellowstone River near Terry

Yellowstone River at Glendive

Yellowstone River near Sidney

Soda Butte Creek

Bighorn River at Kane

Bighorn River at mouth

Clarks Fork Yellowstone River

Tongue River at mouth

Yellowstone River at Corwin Springs

MOUNTAIN

STREAM BASIN STREAMS PLAINSSTREAM YELLOWSTONE RIVER (downstream )

Severely impaired for aquatic life,

fisheries, and contact recreation

Moderately impaired for aquatic life and fisheries,

Moderately impaired

for contact recreation

Unimpaired

and severely impaired for contact recreation

Figure 19. Periphyton chlorophyll-a concentrations during August 2000 exceeded screening-level criteria for the protection of designated uses listed by the Montana Department of Environmental Quality (2003).

Trace elements in ground 

water were generally 

low compared to drinking-water standards and 

guidelines

Nearly all of the concentrations of 

trace elements in the 25 wells completed 

in the Quaternary aquifers were less than 

Federal standards and guidelines. Of the 

29 wells completed in the lower Tertiary 

aquifers, the Federal drinking-water 

standard was exceeded once for antimony, boron, cadmium, and selenium 

and twice for molybdenum. Concentrations of uranium exceeded the Federal 

drinking-water standard of 20 μg/L in 

samples from four wells in the QuaterPeriphyton and invertebrate communities are 

degraded in some

segments of the

Yellowstone River

Low to moderate concentrations 

of algae are desirable because algae 

produce oxygen and provide food and 

shelter for other aquatic life. Excessive 

concentrations of algae, however, can 

result in inadequate dissolved-oxygen 

concentrations, with harmful effects to 

other aquatic life, and can detract from 

esthetic properties and recreational uses. 

Excessive growths of algae typically are 

associated with nutrient enrichment, also 

known as eutrophication.

The periphyton chlorophyll-a

concentrations in the upper segments of 

nary aquifers and two wells in the lower 

Tertiary aquifers.

Some wells contained high concentrations of iron and manganese—both 

trace elements were detected at concentrations greater than USEPA secondary 

drinking-water guidelines of 0.3 mg/L 

for iron and 0.05 mg/L for manganese. 

Although nontoxic, these two elements 

can limit the uses of the ground water 

or require treatment because they can 

cause staining of plumbing fixtures and 

laundry, as well as creating taste and 

odor problems.

20 Water Quality in the Yellowstone River Basin, Wyoming, Montana, and North Dakota, 1999–2001
Figure 20. The high percentage of pollution-intolerant mayflies, stoneflies, and caddisflies 

indicates good water quality and habitat conditions in the upper and lower sections of the 

Yellowstone River, but a lower percentage indicates degraded conditions in the middle 

sections.

0

10

20

30

40

50

60

70

80

90

Clarks Fork Yellowstone River enters

Bighorn River enters

100

RELATIVE ABUNDANCE OF MIDGES AND W

ORMS,

IN PERCENT

RELATIVE ABUNDANCE OF EPT, IN PERCENT

100

90

80

70

60

50

40

30

20

10

0

Yellowstone River at Corwin Springs

Yellowstone River at Livingston

Yellowstone River at Greycliff

Yellowstone River at Laurel

Yellowstone River at Billings

Yellowstone River at Custer

Yellowstone River at Forsyth

Yellowstone River at Miles City

Yellowstone River near Terry

Yellowstone River at Glendive

Yellowstone River near Sidney

Soda Butte Creek

Clarks Fork Yellowstone River

Bighorn River at Kane

MOUNTAIN

STREAM

BASIN

STREAMS YELLOWSTONE RIVER (downstream )

the Yellowstone River at Corwin Springs 

and Livingston were about 20–25 mg/m2

(milligrams per square meter) (fig. 19). 

The maximum concentrations of chlorophyll-a in the Yellowstone River were 

800 mg/m2 at Billings, and 85 mg/m2

at Forsyth, on the middle segments of 

the river. Chlorophyll-a concentrations 

were less than 10 mg/m2 in the lower 

segments of the river, from Miles City 

to Sidney. The maximum concentrations of chlorophyll-a detected in the 

Yellowstone River were at Billings, 

downstream from the confluence with 

the Clarks Fork Yellowstone River, 

and at Forsyth, downstream from the 

confluence of the Bighorn River. Chlorophyll-a concentrations were 110 mg/m2

in the Clarks Fork Yellowstone River 

and 160 mg/m2 in the Bighorn River at 

the mouth (Peterson and Porter, 2002). 

Some of the concentrations of chlorophyll-a sampled at sites in Montana 

exceeded criteria for designated uses 

specified by the Montana Departmental 

of Environmental Quality (2003). Concentrations of chlorophyll-a in samples 

from the Yellowstone River at Billings 

and the Bighorn River at the mouth were 

in the range of severely impaired conditions for the protection of aquatic life 

and fisheries (greater than 150 mg/m2) 

and severely impaired conditions for 

contact recreation (greater than

100 mg/m2) (fig. 19). The concentrations of chlorophyll-a in samples from 

the Clarks Fork Yellowstone River and 

the Yellowstone River at Forsyth were in 

the range of either moderately impaired 

or severely impaired conditions for the 

designated uses.

The types of algae found in the 

periphyton community also indicated 

nutrient enrichment in the middle segments of the Yellowstone River. The 

percentage of algal species indicative of 

eutrophication increased with periphyton biomass, and eutrophic species 

accounted for about 50 percent of algal 

community structure in the middle segments of the river. 

Sources of nutrient enrichment that 

contribute to periphyton growth include 

ammonia from geothermal springs in the 

Yellowstone River headwaters (p. 11) 

and tributary inflows containing nutriand Federal agencies to evaluate stream 

quality and adverse effects potentially 

resulting from physical disturbance 

to habitat and eutrophication, such as 

organic enrichment, high rates of microbial respiration, and inadequate dissolved-oxygen concentrations (Barbour 

and others, 1999; Hilsenhoff, 1987). 

A predominance of mayfly, stonefly, 

and caddisfly species (Ephemeroptera, 

Plecoptera, and Trichoptera—also 

known as EPT— taxa that are pollution intolerant) in streams and rivers 

generally indicates good water quality 

and habitat conditions, whereas aquatic 

communities dominated by midges and 

worms (pollution-tolerant taxa) typically 

reflect degraded or poor water quality 

and habitat.

EPT taxa were predominant in the 

upper segments of the Yellowstone River 

at Corwin Springs and Livingston, as 

well as in lower segments of the river 

from Miles City to Sidney (fig. 20). 

Higher percentages of tolerant midge 

and worm taxa in most of the middle 

ents from natural, agricultural, and rural 

residential sources, notably in the Clarks 

Fork Yellowstone and Bighorn River 

Basins. Water samples collected during 

August 2000 indicated concentrations 

of nitrate, a critical nutrient for algae, 

generally were below reporting limits in 

the Yellowstone River but were higher 

in the Clarks Fork and Bighorn Rivers. 

The apparent lack of nitrate in the Yellowstone River, while at the same time 

the chlorophyll concentrations and algal 

community composition indicated nutrient enrichment, could be a reflection 

of uptake of the nutrient by the algae. 

For example, Dodds (2003) describes 

rapid assimilation of nutrients from the 

water column by a large biomass of 

primary producers, resulting in nutrient concentrations below the reporting 

limits. The seasonal variation in nitrate 

concentrations in the main stem of the 

Yellowstone River (fig. 11, p. 10) likely 

is influenced by algal uptake.

Aquatic invertebrates (aquatic 

insects, snails, and worms) are a biological indicator commonly used by State 

Major Findings 21
Additional Information

For additional information on 

algal and invertebrate communities 

in the Yellowstone River Basin, 

see Peterson and Porter (2002) and 

Peterson and others (2001).

Figure 21. Fish from the Yellowstone River 

at Billings and Forsyth had more anomalies 

and intermediate percentages of introduced and tolerant species compared to 

other sites.

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segments of the river, however, indicate 

somewhat degraded conditions. Tolerant 

taxa dominated the invertebrate community of the Yellowstone River at sites 

downstream from the two largest tributaries, the Clarks Fork Yellowstone and 

Bighorn Rivers. Invertebrate data (EPT 

abundance) indicated degraded conditions in the Clarks Fork Yellowstone 

River but relatively good conditions in 

mountain tributaries. Invertebrates in the 

family Simuliidae (blackfly larvae) were 

common in samples from the Yellowstone River at Livingston and Sidney. 

Blackfly larvae are filter feeders on particulate organic material suspended in 

flowing waters and are associated with a 

wide range of stream conditions.

warm-water fish communities in the 

basin tributaries, plains streams, and 

lower Yellowstone River (fig. 21). Members of the trout family dominated the 

cold-water fish communities; sculpin, 

longnose dace, and suckers also were 

noted. The sites farther downstream on 

the Yellowstone River contained 12 to 

13 species, representing several families 

of warm-water fishes including drum, 

mooneyes, minnows, suckers, catfish, 

pike, and perches. The lower reaches 

of the Yellowstone River contained fish 

such as sauger and sturgeon that are better adapted to warm, turbid water than 

are trout.

Most of the fish captured were 

native species, with exceptions at two 

sites. The fish community of the Tongue 

River, a mountain stream, contained 

a high proportion of brown trout and 

rainbow trout that were introduced to 

enhance the sport fishery. The warmwater fish community of the Little 

Powder River, a plains stream, contained 

many young-of-the-year black bullheads 

that are classified as an introduced species, although that status is not certain 

(Baxter and Stone, 1995). The preponderance of black bullheads also caused 

the Little Powder River to have a higher 

proportion (74 percent) of fish classified as tolerant to environmental stress 

than other sites in 1998 (fig. 21). Five 

fish samples collected from the Little 

Powder River during 1998 to 2002 indicated a substantial year-to-year variation 

in fish communities, with a range of 

16 to 75 percent tolerant fish. Tolerance 

ratings were assigned to fish species 

by using regional and national sources 

such as Zaroban and others (1999) and 

Barbour and others (1999).

The highest rates of anomalies in 

the Yellowstone River Basin were in fish 

from the Yellowstone River at Billings 

and Forsyth, where about 15 to 20 percent of the fish had lesions or eroded 

fins (fig. 21). Although anomalies were 

noted in several species at each site, 

members of the sucker family showed 

the highest rate of anomalies. Eroded 

fins and lesions (Smith and others, 2002) 

were the most common external anomalies in the fish samples from Billings 

and Forsyth. The cause of the anomalies 

Fish communities reflect 

water-quality and habitat 

conditions

Fish-community composition can 

be used as an indicator of environmental 

stresses, such as degraded water quality 

or habitat (Barbour and others, 1999). 

High percentages of introduced species, 

tolerant species, and fish with external 

anomalies reflect environmental stresses, 

whereas lower percentages of such 

species and anomalies are considered 

desirable. External anomalies such as 

deformities, eroded fins, lesions, and 

tumors (DELT) might indicate sublethal 

environmental stresses, intermittent 

stresses, behavioral stresses, or chemically contaminated substrates (Moulton 

and others, 2002).

Cold-water fish communities in 

mountain tributaries and at the uppermost site on the Yellowstone River 

(Corwin Springs) contained few species 

when compared to the more diverse 

is not known. Less than 10 percent of 

the fish collected from the Yellowstone 

River at Forsyth during 2002–03 had 

external DELT anomalies; comparable 

data were not available from the Billings 

site.

22 Water Quality in the Yellowstone River Basin, Wyoming, Montana, and North Dakota, 1999–2001
Electrofishing on the Tongue River near Dayton, 

Wyoming (photograph by Stephen D. Porter,

U.S. Geological Survey).

Basic and intensive stream-sampling sites, Yellowstone River Basin, 1999–2001

Map 

number USGS site identifier Site name

Drainage area

(square miles)

Largest category of 

land cover and land 

use (percent)

1 06187915 Soda Butte Creek at Yellowstone National Park boundary near Silver Gate, Montana 31.2 Forest (66)

2 06191500 Yellowstone River at Corwin Springs, Montana 2,623 Forest (67)

3 06208500 Clarks Fork Yellowstone River at Edgar, Montana 2,032 Range (45)

4 06214500 Yellowstone River at Billings, Montana 11,795 Forest (41)

5 06279500 Bighorn River at Kane, Wyoming 15,765 Range (73)

6 06295000 Yellowstone River at Forsyth, Montana 40,339 Range (58)

7 06298000 Tongue River near Dayton, Wyoming 204 Forest (74)

8 06324970 Little Powder River above Dry Creek near Weston, Wyoming 1,235 Range (84)

9 06326500 Powder River near Locate, Montana 13,189 Range (82)

10 06329500 Yellowstone River near Sidney, Montana 69,103 Range (65)

MONTANA

WYOMING

N

O

RTH

DA

KOTA

5 7

3

4

6 9

10

8

2

1

8 Basic fixed or intensive sampling

site and number

Bed-sediment and fish-tissue

sampling site

Algal-nutrient study sampling

site

Bacteria synoptic study area

EXPLANATION

Sheridan

Bighorn Basin

ground-water

study area

Lander

Red

Lodge

Bighorn

Basin

Lander

Red

Lodge

W Sheridan ell completed in

Quaternary aquifer

Well completed in

lower Tertiary aquifer

Land-use study well

EXPLANATION

Study Unit Design

The Yellowstone River Basin study 

design blends an assessment of local waterquality issues within a nationally consistent design that incorporates a multiscale, 

interdisciplinary approach consisting of 

stream chemistry, stream ecology, and 

ground-water chemistry (Gilliom and others, 1995) (http://water.usgs.gov/nawqa). 

Surface-water and ecological studies 

focused primarily on the Yellowstone 

River, from its upper reaches near Corwin 

Springs, Mont., to lower segments near 

Sidney, Mont., as well as major tributaries 

draining the residential, agricultural, and 

undeveloped basins, and rangeland plains. 

Ground-water studies focused primarily on 

the Quaternary and lower Tertiary aquifers 

underlying the Bighorn Basin.

Additional Information

Additional information on 

streamflow and chemistry data 

for surface water, ground water, 

fish tissue, and bed sediment 

as well as taxonomic data for 

biota are available at: http://

wy.water.usgs.gov/YELL/htms/

data.htm

Water-quality data and collection and analytical methodologies can be accessed at 

http://water.usgs.gov/nawqa

Study Unit Design 23
Study

component What data are collected and why Number and types of sites sampled Sampling frequency and period

Stream Chemistry

Basic fixed sites Samples were analyzed for major ions, nutrients, 

organic carbon, and suspended sediment. Samples were analyzed for trace elements at five sites. 

Selected samples were analyzed for bacteria. 

Daily streamflow data also were collected. Data 

were collected to describe the occurrence and 

distribution of constituents. 

Ten sites, consisting of 6 sites on 

tributaries representing mineralized, forested, rangeland, and mixed 

land-use areas; and 4 sites on the 

Yellowstone River, representing areas 

of mixed land use.

Monthly, plus additional high-flow 

samples, January 1999 through October 

2001.

Intensive fixed sites In addition to data collected for basic fixed sites, 

samples were analyzed for pesticides. Data were 

collected to describe the occurrence of pesticides 

and to refine descriptions of seasonal variability 

of multiple constituents.

Three of the basic fixed sites representing areas with more intensive 

agricultural land use.

Biweekly to monthly plus additional 

high-flow samples, January 1999 

through December 1999.

Bacteria synoptic Samples were analyzed for fecal coliform and 

Escherichia coli to determine the distribution and 

abundance of coliform bacteria.

One hundred sites on small and large 

streams with varying land use in 

the Wind River, Bighorn River, and 

Goose Creek Basins of Wyoming.

June and July 2000.

Stream Ecology

Basic and intensive 

fixed sites

Measurements of instream habitat and riparian 

areas, and samples of algae, invertebrates, and 

fish community. Biological and habitat indicators 

of stream quality.

Stream sizes included three small, 

wadeable tributaries that were landuse indicator sites, larger tributaries that integrated land uses in the 

basins, and four large river sites on 

the main stem Yellowstone River.

All were sampled once during AugustSeptember 1999.

Multiyear and multireach sitesMeasurements of habitat and samples of algae, 

invertebrates, and fish community. To test variability between years and between reaches.

Two fixed sites were selected for 

multiyear sampling, and one site for 

multireach sampling.

Multiyear sites were sampled once 

per year during 1999–2001 for all 

data types, and in 1998 for fish. Three 

reaches were sampled at one site once 

during 2001.

Bed-sediment and 

fish-tissue survey

Bed-sediment and fish-tissue samples were analyzed for organic compounds and trace elements, 

to determine occurrence and distribution.

Twenty-four sites were sampled, 

including the 10 basic and intensive 

sites, and 14 other land-use indicator

and integrator sites.

Once during July to September 1998.

Algal-nutrient study Samples of nutrients, algae, invertebrates, and 

measurements of water properties and selected 

habitat characteristics, to evaluate the trophic condition of the Yellowstone River and tributaries.

Samples were collected at 11 sites on 

the main stem Yellowstone River and 

five sites on tributaries.

Once during August 2000.

Ground-Water Chemistry

Major aquifer 

survey—Quaternary 

unconsolidated-deposit aquifers

Major ions, trace elements, nutrients, volatile 

organic compounds, pesticides, pesticide breakdown products, and radiochemicals (including 

radon). To broadly assess water quality in these 

aquifers.

Twenty-four monitoring wells installed for this study plus 1 domestic 

well.

Once in October 1999 to March 2000.

Major aquifer survey—lower Tertiary 

aquifers

Major ions, trace elements, nutrients, volatile 

organic compounds, pesticides, pesticide breakdown products, and radiochemicals (including 

radon). To broadly assess water quality in these 

aquifers.

Fifteen domestic wells, 8 wells 

used for both domestic and stock 

purposes, and 6 stock wells.

Once in July 2000 to June 2001.

Land-use monitoring 

well survey

Major ions, trace elements, nutrients, volatile 

organic compounds, pesticides, pesticide breakdown products, methylene blue active substances, 

chlorofluorocarbons (for age dating), and radon. 

To determine the effects of land use on shallow 

ground-water quality in these aquifers.

Installed 29 wells about 5 to 10 

feet below the water table underlying low-density development 

surrounding Sheridan (Wyoming), 

Lander (Wyoming), and Red Lodge 

(Montana).

Once in June to September 2001.

24 Water Quality in the Yellowstone River Basin, Wyoming, Montana, and North Dakota, 1999–2001
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References Cited 27
28 Water Quality in the Yellowstone River Basin, Wyoming, Montana, and North Dakota, 1999-2001

Glossary

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

will yield usable quantities of water to a well.

Basic fixed sites Sites on streams at which streamflow is 

measured and samples are collected for temperature, salinity, 

suspended sediment, major ions and metals, nutrients, and organic 

carbon to assess the broad-scale spatial and temporal character 

and transport of inorganic constituents of streamwater in relation 

to hydrologic conditions and environmental settings. 

Biological indicator A quantitative measure of biological conditions that may reflect habitat disturbance, chemical contamination, or naturally harsh conditions. The status of algae, invertebrates (insects, worms, and clams), or fish provides a record of 

water quality and stream conditions that water-chemistry indicators might not reveal. 

Chlorofluorocarbons A class of volatile compounds consisting 

of carbon, chlorine, and fluorine. Commonly called freons, and 

have been used in refrigeration mechanisms, as blowing agents in 

the fabrication of flexible and rigid foams, and, until several years 

ago, as propellants in spray cans.

DDT Dichloro-diphenyl-trichloroethane. An organochlorine 

insecticide no longer registered for use in the United States.

Dissolved solids Amount of minerals, such as salt, that are 

dissolved in water; amount of dissolved solids is an indicator of 

salinity or hardness.

Drinking-water standard or guideline A threshold concentration in a public drinking-water supply, designed to protect human 

health. As defined here, standards are U.S. Environmental Protection Agency regulations that specify the maximum contamination levels for public water systems required to protect the public 

welfare; guidelines have no regulatory status and are issued in an 

advisory capacity.

Eutrophication The process by which water becomes enriched 

with plant nutrients, most commonly phosphorus and nitrogen.

Flow-weighted average A concentration calculated by first 

multiplying each sample concentration by its associated streamflow value, then dividing the sum of these products by sum of the 

streamflows. The resultant mean value accounts for the effects of 

variable streamflow on concentrations.

Major ions Constituents commonly present in concentrations 

exceeding 1.0 milligram per liter. Dissolved cations generally are 

calcium, magnesium, sodium, and potassium; the major anions 

are sulfate, chloride, fluoride, nitrate, and those contributing to 

alkalinity, most generally assumed to be bicarbonate and carbonate.

Indicator sites Stream sampling sites located at outlets of 

drainage basins with relatively homogeneous land use and physiographic conditions; most indicator-site basins have drainage areas 

ranging from 20 to 200 square miles.

Integrator or mixed-use site Stream sampling site located at 

an outlet of a drainage basin that contains multiple environmental 

settings. Most integrator sites are on major streams with relatively 

large drainage areas. 

Intensive fixed sites Basic fixed sites with increased sampling 

frequency during selected seasonal periods and analysis of dissolved pesticides for 1 year. Most NAWQA Study Units have one 

to two integrator intensive fixed sites and one to four indicator 

intensive fixed sites.

Nonpoint source A contaminant source that cannot be defined 

as originating from discrete points such as pipe discharge. Areas 

of fertilizer and pesticide applications, atmospheric deposition, 

manure, and natural inputs from plants and trees are types of 

nonpoint source contaminant.

Pesticide A chemical applied to crops, rights of way, lawns, or 

residences to control weeds, insects, fungi, nematodes, rodents, or 

other “pests.”

Point-source contaminant Any substance that degrades water 

quality and originates from discrete locations such as discharge 

pipes, drainage ditches, wells, concentrated livestock operations, 

or floating craft.

Polycyclic aromatic hydrocarbon (PAH) A class of organic 

compounds with a fused-ring structure. PAHs result from incomplete combustion of organic carbon (including wood), municipal 

solid waste, and fossil fuels, as well as from natural or anthropogenic introduction of uncombusted coal and oil. PAHs include 

benzo(a)pyrene, fluoranthene, and pyrene.

Semivolatile organic compound (SVOC) Operationally defined 

as a group of synthetic organic compounds that are solventextractable and can be determined by gas chromatography/mass 

spectrometry. SVOCs include phenols, phthalates, and polycyclic 

aromatic hydrocarbons (PAHs).

Stratification Subdivision of the environmental framework. 

The basin is divided into areas that exhibit reasonable homogenous environmental conditions, as determined by both natural 

and human influences. 

Synoptic sites Sites sampled during a short-term investigation 

of specific water-quality conditions during selected seasonal or 

hydrologic conditions to provide improved spatial resolution for 

critical water-quality conditions.

Trace element An element found in only minor amounts (concentrations less than 1.0 milligram per liter) in water or sediment; 

includes arsenic, cadmium, chromium, copper, lead, mercury, 

nickel, selenium, and zinc.

Water year The continuous 12-month period, October 1 

through September 30, in U.S. Geological Survey reports dealing 

with surface-water supply. The water year is designated by the 

calendar year in which it ends and which includes 9 of the 12 

months. Thus, the year ending September 30, 2000, is referred to 

as the water year 2000.

Yield The mass of material or constituent transported by a river 

in a specified period of time divided by the drainage area of the 

river basin. 
Appendix—Water-Quality Data from the Yellowstone River 

Basin in a National Context

29

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34 Water Quality in the Yellowstone River Basin
Coordination with agencies and organizations in the Yellowstone River Basin was integral to the success of this water-quality assessment. We thank those who served as members of our liaison committee.

Federal agencies

U.S. Department of the Interior

Bureau of Land Management

Bureau of Reclamation

National Park Service

Yellowstone National Park

Bighorn Canyon National Recreation 

 Area

U.S. Fish and Wildlife Service

U.S. Environmental Protection Agency

U.S. Department of Agriculture

Forest Service

Natural Resources Conservation 

 Service

Universities

University of Montana, Bozeman

University of Montana, Missoula

University of Wyoming, Laramie

State Agencies

Wyoming Game and Fish Dept. 

Wyoming Dept. of Environmental Quality

Montana Fish, Wildlife, and Parks Dept.

Montana Dept. of Environmental Quality

Wyoming Water Development

 Commission

Wyoming Dept. of Agriculture

Montana Dept. of Natural Resources and

 Conservation

North Dakota Dept. of Health

Wyoming State Engineer

Other public and private organizations

Upper Yellowstone River Task Force

Wind River Environmental Quality Council

Crow Tribes

Northern Cheyenne Tribe

Yellowstone Ecosystem Studies

Local Agencies

County Conservation Districts, Wyoming

 and Montana

Wyoming Association of Conservation

 Districts

Montana Association of Conservation

 Districts

Yellowstone River Coalition of

 Conservation Districts

We thank the following individuals for contributing to this effort. 

Field work to collect water-quality samples was a combined effort from many USGS people from Wyoming and Montana, and 

in particular, Peter Wright and Stacy Kinsey. Their dedication to high-quality work through many miles and sometimes adverse 

weather conditions is greatly appreciated. Others who assisted in similar fashion include Karen Watson, Laura Hallberg, and Jon 

Mason, as well as many others from the Casper, Riverton, Billings, Fort Peck, and Cheyenne offices. We also thank the landowners 

that let us drill wells on their property or allowed us access to sampling sites.

Collection of ecology samples was accomplished by USGS people including Ron Zelt, Stacy Kinsey, Peter Wright, Ivan James, 

Rod DeWeese, Karen Watson, Tommie Leman, Greg Boughton, and others. Field assistance for sampling of fish communities was 

provided by the Wyoming Game and Fish Department, including Bob McDowell, Bill Bradshaw, Bud Stewart, and Mike Welker, as 

well as from Montana Fish, Wildlife, and Parks, including Mike Vaughn, Vic Riggs, and Joel Tohtz. The assistance of Pete Ramirez, 

Kim Dickerson, and Bill Olsen from the U.S. Fish and Wildlife Service also is gratefully acknowledged.

Reviewers of this report during various stages made many helpful suggestions. Guidance from Pixie Hamilton, as well as technical 

comments from many other USGS personnel, such as Steve Kalkhoff, Barb Scudder, Lisa Nowell, Rod DeWeese, and Myron 

Brooks, helped improve the quality of the report. Technical review by Liz Galli-Noble of the Montana Governor’s Upper Yellowstone 

Task Force also is appreciated. Comments from Jeremy Zumberge (Wyoming Dept. of Environmental Quality), Bob McDowell 

(Wyoming Game and Fish Dept.), and Don Skaar (Montana Fish, Wildlife, and Parks) provided excellent insights.

Illustrations and report layout through numerous revisions were skillfully rendered by Sue Roberts. Editorial reviews by Jim Wilson, 

Betty Palcsak, Janet Carter, and Mary Kidd improved the readability of the manuscript. Layout reviews by Ed Swibas and Bob 

Olmstead also improved the readability. Assistance from Chet Zenone, Phil Redman, and Emily Sabado also is appreciated.
Peterson and others— Water Quality in the Yellowstone River Basin 

U.S. Geological Survey Circular 1234

National Water-Quality Assessment (NAWQA) Program

Yellowstone River Basin

NAWQA

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