Available from the U.S. Geological Survey, Branch of Information Services, Box 25286, Denver Federal Center, Denver, CO 80225, USGS Water-Resources Investigations Report 994223, 63 p., 43 figs.
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The Upper Colorado River Basin study unit of the U.S. Geological Survey National Water-Quality Assessment Program consists of the Colorado River watershed upstream from near the Colorado-Utah State line. The basin is about equally divided between the Southern Rocky Mountains and the Colorado Plateau physiographic provinces. Data were collected at pairs of indicator sites for mining, increasing urban development, and agricultural land use. Reference basic fixed sites were established in each physiographic province to provide baseline or background information in areas where anthropogenic influences are minimal.
Water-quality data collection began at three of the sites in water year 1995. Full implementation of data collection at the 14-site network began in October 1996 and continued through September 1998. Six hundred and sixty water-quality samples were collected at the network sites.
Snowmelt runoff dominates the hydrology in most of the basin, but water management for irrigation, storage, and transmountain diversions substantially changes annual runoff characteristics in some areas. Streamflow during water years 1995 and 1997 was generally greater than long-term average conditions. During water year 1996, streamflow also was above average at many sites but not to the extent as seen during 1995 or 1997. Water year 1998 streamflows typically were near or slightly below the long-term average. Extreme low-flow conditions generally did not occur at the sites during the data-collection period.
Dissolved nitrate and total phosphorus concentrations at the background site within the Southern Rocky Mountain physiographic province typically were low (hundreths of milligrams per liter). Concentrations in areas of urban development and areas in the lower parts of the basin generally were in the tenths of milligrams per liter and in some agricultural areas were in the milligram per liter range. Median dissolved-solids concentrations at sites in the Southern Rocky Mountains were typically less than 200 milligrams per liter. Small tributaries in the Colorado Plateau and agricultural areas had dissolved-solids concentrations in the thousands of milligrams per liter range. Trace-element concentrations were high, at times, in areas of mining land use. Median zinc concentration for the French Gulch near Breckenridge site was 2,700 micrograms per liter.
Comparison of measured concentrations to Colorado State instream standards showed that concentrations of dissolved oxygen, pH, nitrate, and ammonia were within instream standards at all sites. Concentrations of cadmium and zinc at the site on French Gulch (a mining-affected site) often were greater than the State instream standard.
Purpose and Scope
Colorado River below Baker Gulch, Station 09010500
French Gulch near Breckenridge, Station 09046530
Gore Creek at Mouth, Station 09066510
Colorado River near Dotsero, Station 09070500
Dry Fork of Roan Creek, Station 09095300
Colorado River near Cameo, Station 09095500
East River below Cement Creek, Station 09112200
Gunnison River at County Road 32 below Gunnison, Station 383103106594200
Gunnison River below Gunnison Tunnel, Station 09128000
Uncompahgre River near Ridgway, Station 09146200
Dry Creek at Begonia Road near Delta, Station 09149480
Gunnison River near Grand Junction, Station 09152500
Reed Wash near Mack, Station 09153290
Colorado River near Colorado-Utah State Line, Station 09163500
Summary and Conclusions
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