MAJOR WATER-QUALITY ISSUES IN 

THE YELLOWSTONE RIVER BASIN

Assessing the water quality in the Yellowstone 

River Basin is important for the protection and 

utilization of the water resources. Changes in 

water quality can affect the entire ecosystem, 

raising concerns about drinking-water quality, 

habitat degradation or destruction, and loss of use 

of the resource. The Yellowstone River Basin 

NAWQA study will increase the scientific 

understanding of surface- and ground-water 

quality and the factors that influence water 

quality. This information will benefit the waterresource managers that need, but often lack, the 

data to implement effective management actions 

and evaluate long-term changes in water quality.

NATIONAL WATER-QUALITY ASSESSMENT PROGRAM

Yellowstone River Basin

1

Assessing the quality of water in every location of the Nation would not be practical; 

therefore, NAWQA Program studies are planned within a set of areas called study units 

(fig. 1). These study units are composed of over 50 important river and aquifer systems that 

represent the diverse geography, water resources, and land and water uses of the Nation. The 

Yellowstone River Basin is one such study unit, designed to include the entire 70,100-

square-mile Yellowstone River drainage. Study activities by the U.S. Geological Survey in 

the Yellowstone River Basin began in 1997.

elements also can be associated with 

suspended sediments in streams.

• Toxic compounds - Potential sources for 

toxic compounds in both ground water and 

streams include: leachate from abandoned 

and active landfills; pesticides and 

fertilizers from lawns and croplands; 

hydrocarbons from leaking tanks, refining 

operations, pipelines, and spills; and waste 

from industrial and commercial activities.

• Salinity - Increases in the salinity of both 

ground water and streams can occur from 

saline ground water disposal, irrigation 

return flows, and some irrigation practices.

• Sedimentation - Loss of streambank 

vegetation, easily erodible soils, and many 

land-use activities can contribute to 

sediment problems in streams throughout 

the basin.

• Other related issues - Other potential 

issues related to water quality in the basin 

include: acidification of water resources by 

leaching of mine spoils, nutrient 

enrichment of ground water and streams 

from fertilizers and animal and human 

waste, localized de-watering of sole-source 

aquifers, ground-water and stream quality 

related to coalbed methane production, 

and water-quality concerns on tribal lands.

Major water-quality issues in the Yellowstone 

River Basin vary from potential degradation of 

pristine streams in headwater areas to industrial 

and agricultural effects in downstream reaches. 

The issues generally are related to effects of land 

and water use, but some are related to natural 

factors.

• Trace elements - Leachate from mine spoils and 

tailings can increase trace elements in both 

ground water and streams. Leaching of soils 

derived from marine shales of Cretaceous age in 

some locations has caused high concentrations 

of selenium in water resources. Geothermal 

areas, like those in the Yellowstone National 

Park area, can be sources of trace elements such 

as arsenic in both ground water and streams. 

Because of the widespread distribution of 

uranium-bearing rocks, elevated 

concentrations of radon and other 

radionuclides in water are a concern. Trace 

WHAT IS THE NAWQA PROGRAM?

During the past 25 years, government and industry have made large financial investments 

aimed at improving water quality across the Nation. Major progress has been made; however, 

many water-quality issues remain. To address the need for consistent and scientifically sound 

information for managing the Nation’s water resources, the U.S. Geological Survey began a 

full-scale National Water-Quality Assessment (NAWQA) Program in 1991. The overall goals 

of the NAWQA Program are to (1) describe current water-quality conditions for a large part 

of the Nation’s freshwater streams and aquifers, (2) describe how water quality is changing 

over time, and (3) improve our understanding of the primary natural and human factors 

affecting water quality.

USGS Fact Sheet 149-97

The Yellowstone 

River originates at the 

Continental Divide in 

Yellowstone National 

Park, Wyoming 

(photo of Lower 

Falls, Yellowstone 

National Park, 

courtesy of Wyoming 

Division of Tourism)

Figure 1. Map showing Yellowstone River Basin NAWQA study unit.
STUDY UNIT DESCRIPTION

The Yellowstone River basin study unit 

extends from central Wyoming north to 

include most of southeastern Montana and a 

small part of western North Dakota. The 

entire Yellowstone River watershed defines 

the study unit boundaries and includes all of 

the Wind/Bighorn, Powder, Tongue, and 

Clarks Fork Yellowstone tributary 

watersheds. Total area for the study unit is 

about 70,100 square miles (sq mi) of which 

51 percent is in Montana, 48 percent is in 

Wyoming, and 1 percent is in North Dakota. 

Total population of the study unit was about 

323,000 (1990 census), of which 206,000 

were in Montana, 116,000 were in Wyoming, 

and 1,000 were in North Dakota.

The study unit lies within the Rocky 

Mountain System and Interior Plains 

physiographic divisions. Topography of the 

study unit in the Rocky Mountain System 

division varies from mountain ranges and 

high plateaus, including the Wind River 

Range, Bighorn Mountains, and Absaroka 

Plateau, to intermontane basins, such as the 

Wind River and Bighorn Basins. The highest 

elevations in the study unit are in the Wind 

River Range, where several peaks exceed 

13,000 feet above sea level. The Interior 

Plains division part of the study unit varies 

from gently rolling plains to sharply 

dissected badlands. The lowest point in the 

study unit, 1,850 feet above sea level, is 

located at the mouth of the Yellowstone 

River in North Dakota.

addition to alluvial sources of ground water, 

sandstone and coal beds within the Fort Union 

Formation of Tertiary age and sandstones in the 

Fox Hills Formation of Upper Cretaceous age are 

important bedrock aquifers. The Wind River 

Formation of Tertiary age is used to supply 

irrigation water in the Riverton, Wyoming area 

with some wells yielding as much as 

3,000 gallons per minute. Other aquifers in 

Mesozoic and Paleozoic units are productive but 

have not been extensively developed.

About 98 percent of the total water used in the 

study unit in 1990 was surface water. Most of this 

water—about 99 percent—was used by the 

agricultural industry for crops and livestock. 

However, ground water is an important resource 

in the study unit. About 97 percent of the 

domestic water supply and about 27 percent of the 

public water supply is from ground water. About 

62 percent of the total ground-water use in 1990 

was for agricultural purposes. Public supply, 

mining, power generation, and industry made up 

most of the remaining uses of surface- and 

ground-water in the study unit.

1Includes Clarks Fork Yellowstone, Wind/Bighorn, 

Tongue, and Powder River Basins.

1

Source: U.S. Geological Survey digital data, 1990.

Drainage area and mean annual streamflow for 

major tributary watersheds, Yellowstone River

[Streamflow data through water year 1996; Note: mean annual 

streamflow is from streamflow-gaging station near mouth of 

respective river.]

River

Drainage area Mean annual 

streamflow

in cubic feet 

per second

Square 

miles

Percent 

of study 

unit

Clarks Fork 

Yellowstone River

2,032 3 1,032

Wind/Bighorn River 22,414 32 3,810

Tongue River 5,397 8 421

Powder River 13,189 19 586

Yellowstone River1 69,103 99 12,750

Reported surface and ground water used by 

category in the Yellowstone River Basin, 19901

[Note: category and total amounts expressed to two significant 

figures.]

Category

Water used in millions of 

gallons per day

Surface water Ground water

Public supply 40 15

Domestic (self-supplied) .21 6.3

Commercial .18 .25

Industrial 16 1.5

Thermoelectric power 33 0

Mining 9.0 37

Agriculture 6,900 93

TOTAL 7,000 150

2 USGS Fact Sheet 149-97

Clarks Fork Yellowstone River valley. Mean 

annual snowfall ranges from more than 130 

inches in Yellowstone National Park to about 

16 inches in northeast Montana.

Rangeland is the dominant land use and 

land cover, with about 43 percent of the 

study unit composed of subhumid grassland 

and semiarid grazing land. The remaining 

land uses and land cover include grazed and 

ungrazed forest (19%), grazed desert 

shrubland (16%), mostly cropland and 

grazed cropland (non-irrigated: 11%; 

irrigated: 5%), grazed open woodland (5%), 

and alpine and lakes (1%).

Grazing by domestic livestock and other species 

on range and grasslands is a major land use in the 

study unit (photo of North American Bison 

courtesy of Wyoming Division of Tourism)

Major land-use industries in the study unit 

include coal and metals mining, oil and gas 

production, and agriculture. About 30 active 

mines remove low-sulfur coal by surface 

strip-mining methods from the large coal 

reserves in the Tongue and Powder River 

Basins. Most of the metals mining occurs in 

the mountainous regions of the study unit. 

Oil and gas is produced from reservoirs in 

the Powder River and Big Horn Basins. 

Much of the agricultural industry in the 

study unit is related to livestock production. 

The agricultural industry also includes 

farming of irrigated cropland along alluvial 

valleys and benches.

Drainage areas for the major tributary 

watersheds range from 22,414 sq mi for the 

Wind/Bighorn River to about 2,032 sq mi for 

the Clarks Fork Yellowstone River. Mean 

annual flow ranges from 12,750 cubic feet 

per second (ft3/sec) for the Yellowstone 

River at Sidney Montana, to about 421 ft3/

sec for the Tongue River near the mouth. 

Streamflow in all the major watersheds is 

affected by diversions. While there are no 

reservoirs on the mainstem Yellowstone 

River, several reservoirs regulate flow in the 

Wind/Bighorn and Tongue River watersheds.

Alluvial deposits of Quaternary age along 

major tributaries and the mainstem Yellowtone River are the primary sources of ground 

water in the study unit upstream of Billings, 

Montana. Downstream from Billings, in 

The Wind River flows 

north through the 

Wind River Canyon 

into the Bighorn 

Basin, where it 

becomes the Bighorn 

River at the Wedding 

of the Waters (photo 

courtesy of Wyoming 

Division of Tourism)

Climate in the study unit ranges from cold 

and moist in the mountainous areas to 

temperate and semiarid in the plains areas. 

Annual temperature extremes range from 

about 30 degrees Fahrenheit (o

F) below zero 

during the winter to hotter than 100oF during 

the summer. Mean annual temperatures 

range from 32oF at Cooke City, Montana to 

48oF at Billings, Montana. Mean annual 

precipitation ranges from more than 60 

inches in the mountains near Yellowstone 

National Park to less than 6 inches in the 
SCHEDULE OF STUDY UNIT ACTIVITIES

The Yellowstone River Basin study is one of a set of 

NAWQA studies started in 1997. Planning, study 

design, and analysis of existing data will occur during 

the first two years of the study (fig. 2). After the 2-year 

planning period, ground-water, surface-water, and 

biological data will be collected intensively for 3 years, 

a period referred to as the high-intensity phase. A lowintensity phase follows for 6 years, during which water 

quality will be monitored at selected sites and areas 

assessed during the high-intensity phase. This cycle 

(without the planning period) will be repeated starting 

in 2007. This combination of high- and low-intensity 

monitoring phases allows the NAWQA Program to 

examine trends in water quality over time.

During the planning period, existing data and results 

from previous studies will be reviewed to help 

understand the primary physical, chemical, and 

biological factors that affect water quality in the study 

unit and to identify gaps in the current data. 

Descriptions of how land use and land cover, soil, 

geology, physiography, climate, and drainage 

characteristics may influence water quality are to be 

included in technical and non-technical reports. The 

existing information, along with field checks of 

existing monitoring stations and possible sampling 

sites, and field reconnaissance data, will be used to 

design a sampling program for the study unit.

During the high-intensity phase, new waterquality and biological data will be collected from 

selected areas at both local and regional scales to 

describe water-quality conditions across the study 

USGS Fact Sheet 149-97 3

unit. Measurements will be 

made and samples will be 

collected and analyzed to 

determine the water chemistry 

in streams and aquifers; the 

quantity of suspended sediment 

and quality of bottom 

sediments in streams; the variety 

and number of fish, benthic 

invertebrates, and algae in 

streams; and the concentrations 

of contaminants, if present, in 

fish tissues. Individual streams, 

aquifers, and biological species 

representative of the primary 

water resources and waterquality concerns for both the 

study unit and the Nation will be 

selected for sampling and 

analysis of particular chemical 

constituents. During the lowintensity phase, monitoring will 

continue at selected sites to 

identify long-term trends. A 

series of technical and nontechnical reports describing 

water-quality concerns are 

planned.

SUGGESTIONS FOR 

FURTHER READING

Gilliom, R.J., Alley, W.M., and 

Gurtz, M.E., 1995, Design of 

the National Water-Quality 

Assessment Program: 

Occurrence and distribution of 

water-quality conditions: U.S. 

Geological Survey Circular 

1112, 33 p.

Leahy, P.P., Rosenshein, J.S., and 

Knopman, D.S., 1990, 

Implementation plan for the 

Nation Water-Quality 

Assessment Program: U.S. 

Geological Survey Open-File 

Report 90-174, 10 p.

Figure 3. Topography, generalized physiography and hydrography, and selected towns and geographic 

features, Yellowstone River Basin.

Figure 2. Timeline of study unit activities.
ASSESSING WATER QUALITY IN 

THE YELLOWSTONE RIVER 

BASIN STUDY UNIT

All NAWQA studies have several common 

components designed to assess water quality 

across the Nation. Consistent data-collection 

and assessment methods make this possible and 

are critical for providing uniform and 

comparable information on water quality for 

the Nation. Surface-water, ground-water, and 

ecological studies will be done at local (a few 

square miles to hundreds of square miles) and 

regional (thousands of square miles) scales to 

understand the water-quality conditions and 

issues in a study unit. The data from all the 

NAWQA studies are aggregated to provide 

national water-quality assessments. 

Partnerships and cooperative studies between 

local, State, and Federal agencies can be 

developed to help meet specific needs. The 

following discussions describe the surfacewater, ground-water, and ecological monitoring 

components of the Yellowstone River Basin 

NAWQA study. The basic design described in 

the following sections is similar among 

NAWQA study units nationwide.

Surface Water

Surface water is monitored at stream sites. 

These sites are classified as basic-fixed sites or 

intensive-fixed sites, according to the frequency 

of the sampling and the types of data collected. 

These sites are used to monitor water-quality 

characteristics such as basic field parameters 

and concentrations of major ions, nutrients, 

pesticides, and possibly volatile organic 

compounds (VOCs) and trace elements. These 

sites are selected to determine water-quality 

conditions in relation to important 

environmental settings in the study unit. Most 

NAWQA study units have about eight basicfixed and four intensive-fixed sites. Basic-fixed 

sites are sampled on a regular basis, typically 

monthly, for the duration of the 3-year highintensity phase. The intensive-fixed sites are 

monitored frequently, typically weekly during 

key time periods, at least for 1 year, to 

characterize short-term variations of water 

quality.

Basic-fixed or intensive-fixed sites can be 

classified as either indicator or integrator sites. 

Indicator sites represent relatively 

homogeneous and usually small basins 

associated with environmental settings, such as 

a specific land use that is considered to be 

important for understanding water-quality in 

the study unit. Integrator sites are established at 

downstream points in large drainage basins, 

which are relatively heterogeneous, and 

incorporate complex combinations of land-use 

settings. These sites represent many of the land 

uses in the basin.

Other types of samples also are collected 

from surface water. Synoptic sampling is done 

as short-term investigations of specific waterquality conditions during selected hydrologic 

periods, such as low streamflow, to provide 

greater spatial data coverage and to allow 

investigators to assess basic-fixed or intensivefixed sites are representative of streams 

throughout the study unit.

Ground Water

Ground-water studies of a typical NAWQA 

study are composed of three components: (1) 

sub-unit survey, (2) land-use studies, and (3) an 

optional flow-path study. The sub-unit survey is 

intended to characterize water quality in the 

major aquifers of the study unit and does not 

target specific land uses. Several wells are 

randomly selected to be sampled in aquifer 

subunits throughout the study unit.

The land-use survey attempts to characterize 

ground-water quality associated with recentlyrecharged water in particular land uses. Landuse studies emphasize the study of shallow 

aquifer systems so that the influences of both 

land-use practices and natural conditions can 

be assessed. Several wells are randomly 

selected within each land use for each aquifer 

type. Ground-water samples are analyzed for 

major ions, nutrients, pesticides, VOCs, and 

trace elements. Results from the land-use study 

can be used to compare with results from the 

sub-unit survey to determine the effect of land 

use on ground-water quality.

The flow-path study is intended to answer 

important questions about processes 

controlling shallow ground-water movement 

and quality. The flow-path study is designed to 

trace the chemical changes that occur to water 

as it enters the ground-water flow system, 

travels along a flow path, and eventually 

discharges. Water samples collected from 

several existing or newly installed wells are 

analyzed for representative constituents.

Ecology

Ecological studies are conducted along with 

the surface-water and ground-water sampling 

activities. Aquatic biological communities are 

surveyed at the basic and intensive fixed sites 

during the three years of the high-intensity 

sampling phase. These investigations are 

conducted along a delineated stream reach and 

include an aquatic and riparian habitat 

assessment of the site and annual surveys of the 

fish, algal, and benthic invertebrate 

communities. This approach is intended to 

provide insight into ecological variability over 

time, the role that water quality plays in 

community structure and stability, and 

differences with respect to various 

environmental settings. Additionally, studies 

are conducted to provide overviews of the 

COMMUNICATION AND 

COORDINATION

Communication and coordination 

between the U.S. Geological Survey and 

other scientific and land- and watermanagement organizations are critical 

components of the NAWQA Program. Each 

study-unit investigation maintains a liaison 

committee consisting of representatives from 

Federal, State, and local agencies, 

universities, the private sector, watershed 

organizations, and those who have waterresource responsibilities and interests. 

Activities include the exchange of 

information about regional and local waterquality issues, identification of sources of 

data and information, assistance in the 

design and scope of study products, and the 

review of study planning documents and 

reports. The Yellowstone River Basin liaison 

committee will be formed in 1997.

The overall success of the Yellowstone 

River Basin NAWQA study will depend on 

the advice, cooperation, and information 

from the public and many Federal, State, 

regional, and local agencies concerned about 

the basin’s water resources. The assistance 

and suggestions of all are welcome.

4 USGS Fact Sheet 149-97

FOR MORE INFORMATION

Information on technical reports and hydrologic 

data related to the NAWQA Program can be 

obtained from:

Tom Quinn, NAWQA Chief

U.S. Geological Survey

Water Resources Division

2617 East Lincolnway, Suite B

Cheyenne, Wyoming 82001-5662

(307) 778-2931

E-mail: nawqamail@mailcheyenne.cr.usgs.gov

Internet:

http://wyoming.usgs.gov/YELL/yell.html

By: Kirk Miller and Tom Quinn

Layout by: Sue Roberts and Kirk Miller; 

modified from Glo Morrill and Jim Caras

ecological status of the study unit. Trace elements 

and synthetic organic compounds are analyzed in 

bed sediment and fish tissue at selected sites to 

determine their occurrence and distribution in the 

study unit. Ecological synoptic studies are 

conducted within a network of sites to evaluate 

spatial variability of biological communities or to 

address issues of special concern within the study 

unit.