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<br />the summer are a primary source of streamflow in plateau areas.
<br />Annual precipitation varies from less than 12 inches in the pla-
<br />teau regions to the west to more than 40 inches over the moun-
<br />tains to the east. Annual runoff in the study area ranges from
<br />0.5 inch throughout much of the basin to more than 20 inches
<br />in the high mountains.
<br />Little ground-water information is available for the Upper
<br />Colorado River Basin because most of the area is unsuitable for
<br />extensive ground-water development and surface-water sup-
<br />plies usually are available. The most productive wells in the
<br />area are completed in unconsolidated deposits including allu-
<br />vium, gravel, landslide deposits, terrace deposits, and glacial
<br />deposits. Yields of wells completed in these deposits normally
<br />are greater than 10 gallons per minute and range from 1 to 750
<br />gallons per minute. Wells completed in bedrock are in the
<br />Eagle Valley Evaporite, Maroon Formation, Burro Canyon For-
<br />mation, Dakota Sandstone, Mancos Shale, Mesaverde Group,
<br />Green River Formation, Precambrian rock, and basalt units.
<br />These wells generally are present at higher altitudes above river
<br />and stream valleys and typically yield an average of about 18
<br />gallons per minute and range from 1 to 60 gallons per minute.
<br />Regional ground-water-flow directions are similar to surface-
<br />water-flow directions. Recharge from precipitation occurs in
<br />mountainous terrain generally in the eastern part of the study
<br />area, flows westward and discharges to springs and surface
<br />water in lower topographic terrain generally in valleys and in
<br />the western part of the study area.
<br />
<br />Water and Land Use
<br />
<br />Management of water resources in the Upper Colorado
<br />River Basin is strongly influenced by the 1922 Colorado River
<br />Compact and the 1948 Upper Colorado River Basin Compact.
<br />The Colorado River Compact formally divided the basin and
<br />apportioned the beneficial consumptive use. The Upper Colo-
<br />rado River Basin Compact apportioned the water of the Upper
<br />Colorado River Basin among the five States having drainage
<br />areas that contribute to the flow of the Colorado River upstream
<br />from Lees Ferry, Arizona. Management of water quality in the
<br />study area has been greatly influenced by three Public Laws.
<br />Public Law 92-500, enacted in 1972, required the establish-
<br />ment of criteria for dissolved-solids concentration in the Colo-
<br />rado River. In 1974, Public Law 93-320 authorized the
<br />construction of 4 salinity-control projects and the development
<br />of plans for 12 others. The 1984 amendment to the act (PL98-
<br />589) provided authority to the Bureau of Reclamation and the
<br />U.S. Department of Agriculture to install salinity controls
<br />needed to meet criteria for dissolved-solids concentrations.
<br />The transmountain diversions from the western to the east-
<br />ern slope of the Continental Divide averaged about 510,000
<br />acre-feet per year from 1973 to 1982, which is less than 12 per-
<br />cent of the average annual streamflow at the mouth of the
<br />Upper Colorado River Basin. These transmountain diversions
<br />generally supply irrigation and municipal water to farms and
<br />cities in the South Platte, Arkansas, and Rio Grande drainages.
<br />Off-stream water use in the Upper Colorado River Basin
<br />during 1990 totaled about 3,535 million gallons per day. About
<br />99 percent of the water used was surface water. About 96 per-
<br />cent of the total water use was for irrigation.
<br />Storage of surface water in lakes and reservoirs in the study
<br />area exceeds 2.3 million acre-feet. Most of this storage is asso-
<br />ciated with three large water-resources development projects:
<br />(I) Currecanti Unit of the Colorado River Storage Project; (2)
<br />Colorado-Big Thompson Project; and (3) municipal water sup-
<br />ply for the Denver metropolitan area.
<br />Land designated for use as rangeland or woodland com-
<br />prises about 85 percent of the Upper Colorado River Basin.
<br />Livestock production is the principal use of the large areas of
<br />rangeland available for foraging. Many of the mountain slopes
<br />and plateau areas are forested. Commercial tree species
<br />include lodgepole pine, Engleman spruce, and Douglas fir.
<br />Other prinicipalland-use designations include cropland, recre-
<br />ation land, and urban land.
<br />Irrigated agriculture is a principal land use in the study area
<br />and uses about 4,000 million gallons per day. Crops that are
<br />irrigated include livestock feed, fruit, and vegetables. Most of
<br />the irrigated lands are in river valleys or on plateaus and are
<br />supplied by extensive systems of canals and ditches. Large
<br />parts of the study area have been set aside specifically for rec-
<br />reational activities. All or part of four National Park Service
<br />recreational areas and four wilderness areas are located in the
<br />
<br />" us. GOVERNMENT PRINTING OFFICE, 1994-840- 799
<br />
<br />study area. More than 10 ski areas operate in the area, and
<br />snow making during low-flow conditions can affect stream
<br />quantity and quality. Mining brought the first settlers to the
<br />region and is still the major industry in many areas. Molybde-
<br />num, vanadium, copper, nickel, uranium, lead, zinc, oil shale,
<br />coal, and oil and gas resources all have been mined in the study
<br />area. Urban land is the smallest land-use category in the study
<br />area. However, several metropolitan areas (Denver, Colorado
<br />Springs) outside the basin have a marked effect on water and
<br />land use in the basin as a result of transbasin diversions.
<br />
<br />MAJOR WATER-QUALITY ISSUES
<br />
<br />The major water-quality issues in the Upper Colorado
<br />River Basin relate to land and water use and differ in the head-
<br />waters and downstream areas. The primary nonpoint-source
<br />activities are irrigated and non irrigated agriculture, grazing,
<br />streamflow regulation from dams and diversions, and recre-
<br />ation. Primary point-source activities are mining-related indus-
<br />try, agricultural-related industry, and municipal wastewater-
<br />treatment facilities. Both point- and nonpoint-source activities
<br />can affect the stream biota and habitat.
<br />The following water-quality issues have been identified, in
<br />conjunction with the Upper Colorado River Basin liaison com-
<br />mittee, as high priority regional-scale issues of concern to the
<br />State and local water-resource managers. The liaison commit-
<br />tee consists of representatives from Federal, State, and local
<br />agencies, universities, and the private sector who have water-
<br />resources responsibilities.
<br />. Effects of sediment, nutrients, and organic compounds from
<br />increasing urban development, including transportation
<br />routes and construction, on the biology and water quality of
<br />receiving streams and affected ground waters.
<br />. Effects of hydrologic modification (transbasin, channel mod-
<br />ification, dams) on water quality and biology of receiving
<br />streams.
<br />. Effects of metals, sediment, and salinity from mineral and
<br />energy extraction on the biological and chemical quality of
<br />receiving waters, particularly in the headwaters of the Colo-
<br />rado River and its tributaries.
<br />. Effects of nutrients, trace elements, pesticides, and sediment
<br />from nonpoint- and point-agricultural sources on the water
<br />quality and biology of receiving streams and affected ground
<br />waters.
<br />. Effects of salinity from natural, agricultural, and municipal
<br />sources on the water quality of receiving streams.
<br />Additional water-quality issues that were identified by the
<br />liaison committee as lower priority issues are listed below.
<br />. Identify high quality water-quality conditions
<br />. Determine quality of water in wetlands and effects of land-
<br />use practices on wetlands.
<br />. Effects on downstream users
<br />. Effects from municipal wastewater-treatment plants
<br />. Effects of recreational uses
<br />
<br />COMMUNICATION AND COORDINATION
<br />
<br />Communication and coordination between the U.S. Geo-
<br />logical Survey and water-management and other water-
<br />resource organizations are critical components of the NAWQA
<br />program. Study-area liaison committees have proven to be
<br />highly effective in increasing communication and collabora-
<br />tion. Specific activities of the Upper Colorado River Basin
<br />liaison committee include:
<br />. Exchanging information on and prioritizing water-quality
<br />issues of regional and local interest.
<br />. Identifying sources of water-quality data and other ancillary
<br />information including but not limited to land use, demo-
<br />graphics, soils, land-management practices, and pesticide-
<br />use statistics.
<br />. Assisting in the design and scope of project elements.
<br />. Reviewing project-planning activities, findings, and inter-
<br />pretations, including reports.
<br />Information on technical reports and hydrologic data
<br />related to the NAWQA program can be obtained from:
<br />
<br />District Chief
<br />U.S. Geological Survey
<br />Denver Federal Center
<br />Box 25046, Mail Stop 415
<br />Denver, Colorado 80225
<br />Open File Report 94-102
<br />
<br />N.E. Driver, 1994
<br />
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