Impacts of selenium-laden drainwater on fish from two irrigation projects in westcentral Colorado
Irrigation began in both Uncompahgre and Grand Valley Project areas in the 1880`s. The Uncompahgre Project irrigates about 86,000 acres, of which over 60 percent is west of the Uncompahgre River and on soils derived from terrace deposits and Dakota Sandstone. About 34 percent of irrigated land in the Uncompahgre Project is east of the river and on soils derived primarily from seleniferous Mancos shale. Selenium concentrations were higher in surface water, aquatic plant, aquatic invertebrate, and fish samples collected east of the Uncompahgre River compared to those collected west of the Uncompahgre River, and often exceeded guideline concentrations of concern. The Grand Valley Project irrigates about 70,000 acres of which one-half is served by the Federal irrigation project. Most of the irrigated land in the Grand Valley is on soils derived or partially derived from Mancos shale. Selenium concentrations in most surface water and fish samples collected in Grand Valley tribs exceeded concern concentrations. Intensive fish sampling was done at 11 sites on mainstem Uncompahgre, Gunnison, and Colorado Rivers, which all receive irrigation drainwater from the Grand Valley and Uncompahgre Projects. Selenium concentrations in Gunnison River fish were significantly higher than those collected from the other two rivers. Speckled dace contained significantly higher selenium concentrations than roundtail chubs or sucker species. Both the Gunnison and Colorado Rivers contain occupied and critical habitat for at least two endangered fish species. Selenium from these two irrigation projects may have an adverse impact on the endangered fish.
- OSTI ID:
- 40190
- Report Number(s):
- CONF-9410273--
- Country of Publication:
- United States
- Language:
- English
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