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Figure 1. Map showing Yellowstone River Basin NAWQA studty unit. |
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.
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.
MAJOR WATER-QUALITY ISSUES IN THE YELLOWSTONE RIVER BASIN |
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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 water-resource
managers that need, but often lack, the data to
implement effective management actions and evaluate
long-term changes in water quality.
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.
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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.
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 (°F) below zero during the winter to hotter than 100°F during the summer. Mean annual temperatures range from 32°F at Cooke City, Montana to 48°F 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 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%).
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 Yellow-tone River are the primary sources of ground water in the study unit upstream of Billings, Montana. Downstream from Billings, in 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.
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Figure 2. Timeline of study unit activities. |
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Figure 3. Topography, generalized physiography and hydrography, and selected towns and geographic features, Yellowstone River Basin. |
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 water-quality and biological data will be collected from selected areas at both local and regional scales to describe water-quality conditions across the study 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 water-quality concerns for both the study unit and the Nation will be selected for sampling and analysis of particular chemical constituents. During the low-intensity phase, monitoring will continue at selected sites to identify long-term trends. A series of technical and non-technical reports describing water-quality concerns are planned.
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 water-quality conditions during selected hydrologic periods, such as low streamflow, to provide greater spatial data coverage and to allow investigators to assess basic-fixed or intensive-fixed sites are representative of streams throughout the study unit.
The land-use survey attempts to characterize ground-water quality associated with recently-recharged water in particular land uses. Land-use 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.
COMMUNICATION AND COORDINATIONCommunication and coordination between the U.S. Geological Survey and other scientific and land- and water-management 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 water-resource responsibilities and interests. Activities include the exchange of information about regional and local water-quality 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.
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SUGGESTIONS FOR FURTHER READING |
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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. |
FOR MORE INFORMATIONInformation on technical reports and hydrologic data related to the NAWQA Program can be obtained from:Tom Quinn, NAWQA Chief By: Kirk Miller and Tom Quinn |
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