Selenium

The east side of the Uncompahgre River Basin has been a known contributor of dissolved selenium to recipient streams. Discharge of groundwater containing dissolved selenium contributes to surface-water selenium concentrations and loads; however, the groundwater system on the east side of the Uncompahgre River Basin is not well characterized.

In response to the need for more information about selenium (Se) sources and transport, the U.S. Geological Survey, in cooperation with the Colorado Water Conservation Board, completed a study that characterized Se loads in a reach of the Gunnison River between Delta and Grand Junction, Colo. This study identifies where possible dissolved Se loading is occurring in a study reach in the Lower...

The Selenium Management Program (SMP) seeks to identify and mitigate selenium sources thereby decreasing levels in endangered fish habitat in the Gunnison River and tributaries. As part of the SMP process, the U.S. Geological Survey (USGS) was asked to develop a Selenium Science Plan to help identify data gaps and prioritize scientific studies needed.

Selenium (Se) and salinity (total dissolved solids) are water-quality concerns in much of the arid western US where agricultural and urban irrigation overlie Cretaceous-age shale. Leaching of Se and salinity from shale can degrade water quality and negatively affect aquatic biota in receiving water bodies. Since 1985 programs In the upper Colorado River Basin have worked to reduce Se and salinity...

High concentrations of dissolved selenium have been detected in the lower Gunnison River basin including the Uncompahgre River basin. Butler and others (1991 and 1996) identified the highest concentrations of selenium in surface waters in areas that are irrigated on soils derived from Mancos Shale. In July 1997, the Colorado Water Quality Control Commission amended the classifications and numeric...