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<br />O~Z3Jl <br /> <br />RECONNAISSANCE INVESTIGATION OF WATER QUALITY, BOTTOM SEDIMENT, <br />AND BIOTA ASSOCIATED WITH IRRIGATION DRAINAGE IN THE GUNNISON <br />AND UNCOMPAHGRE RIVER BASINS AND AT SWEITZER LAKE, <br />WEST-CENTRAL COLORADO, 1988-89 <br /> <br />By David L. Butler, Richard P. Krueger, Barbara Campbell Osmundson, <br />Andrew L. Thompson, and Steven K. McCall <br /> <br />ABSTRACT <br /> <br />During the last several years, there has been increasing concern about <br />the quality of irrigation drainage and its potential harmful effects on human <br />health, fish, and wildlife. This report describes the results of a reconnais- <br />sance investigation done during 1988-89 of the Uncompahgre Project, located in <br />west-central Colorado. Water, bottom sediment, and biota samples were col- <br />lected in the Gunnison and Uncompahgre River basins, and at Sweitzer Lake to <br />identify potential water-quality problems that could be associated with the <br />Uncompahgre Project. The Uncompahgre Project was selected for a reconnais- <br />sance investigation because unusually large selenium concentrations have been <br />reported in the Gunnison River downstream from the project and in fish from <br />Sweitzer Lake. <br /> <br />Irrigation drainage from the Uncompahgre Project area contributes dis- <br />solved solids, sodium, sulfate, nitrite plus nitrate, selenium, boron, and <br />uranium to the Gunnison and Uncompahgre Rivers. Selenium concentrations <br />in some of the water samples collected from both rivers exceeded U.S. <br />Environmental Protection Agency criteria for protection of aquatic life and <br />the concentrations may be of concern for fish and waterfowl because of food- <br />chain biocentration. The largest concentration of selenium from the Gunnison <br />River was 10 micrograms per liter in a sample collected in July 1988 upstream <br />from Escalante Creek. The largest selenium concentrations in the Uncompahgre <br />River were in samples collected at Delta; concentrations were 33 micrograms <br />per liter in November 1987 and 34 micrograms per liter in January 1988. The <br />insecticide parathion was detected at concentrations exceeding the criteria <br />for protection of aquatic life in both the Gunnison and Uncompahgre Rivers in <br />samples collected in July 1988. <br /> <br />Irrigation-drainage water discharging into Sweitzer Lake contributes <br />dissolved solids, sodium, sulfate, nitrite plus nitrate, and selenium to the <br />lake during the nonirrigation season. The maximum concentrations of dissolved <br />solids, sodium, sulfate, selenium, boron, and uranium were in samples col- <br />lected during January and March 1988 from the Garnet Canal diversion at <br />Sweitzer Lake; selected maximum constituent concentrations were: <br />12,700 milligrams per liter of dissolved solids, 320 micrograms per liter of <br />selenium, 800 micrograms per liter of boron, and 64 micrograms per liter of <br />uranium. Water in the Garnet Canal during the nonirrigstion season probably <br />is irrigation-drainage water. <br /> <br />1 <br />