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Emerging water-quality issues within Delta, Montrose, and Mesa counties reflect changing land use practices, housing development and related pressures due to growth. Significant amounts of data have been collected by members of the Gunnison Basin Selenium Task Force as it relates to selenium related water-quality problems.
Soils within a large portion of the lower Gunnison Basin are derived from Mancos Shale which has naturally high concentrations of selenium and salts. The Loutzenhizer Arroyo sub-basin has been identified by the Bureau of Reclamation as the most significant selenium loading source in the area; consequently it exhibits the highest average selenium concentrations in the Valley.
Previous studies have also found that in areas containing soils and outcrops with high salt content, such as in the Mancos Shale on the east side of the Uncompahgre Valley, considerable salt loading occurs from canal and lateral leakage. Because Mancos Shale is a major source for selenium, it follows that canal lining and lateral piping significantly decreases selenium loading. This was proven in 1998 when the Montrose Arroyo Piping Project data demonstrated that significant selenium reduction benefits occur when salinity-control type projects (e.g. lining or piping) are implemented. The Montrose Arroyo post project monitoring showed reduced seepage, groundwater levels, and selenium and salt loads.
The U.S. Geological Survey (USGS), in cooperation with Delta County and the Shavano Soil Conservation District, developed a characterization study to provide more detailed selenium information for the lower Gunnison River Basin.
The selenium characterization study objectives are:
Below are publications associated with this project.
Below are partners associated with this project.