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<br />. <br /> <br />. <br /> <br />. <br /> <br />o <br />~'" <br />CJl <br />CD <br /> <br />Based on results of the detailed study, additional work was initiated in 1995 in the Lower <br />Gunnison Basin (Uncompahgre Project) and the Grand Valley for the purposes of planning for <br />remediation. A study team headed by the Bureau of Reclamation, with members from the U.S. <br />Geological Survey and the Fish and Wildlife Service, directed the remediation planning efforts. <br />Through 1997, selenium and salinity data have been collected for several major washes in the <br />Uncompahgre and Grand Valleys and for the mainstem rivers. Selenium and salt loads have <br />been estimated for these sites. There are significant correlations between selenium and salt <br />concentrations and loads for specific watersheds in the irrigated areas. The use of <br />salinity-control projects as a possible selenium-remeadiation tool are under consideration. <br /> <br />Trends and Changes in Dissolved Solids and Streamflow in the Colorado <br />River Basin Upstream from Lake PoweU <br /> <br />A study of salinity and streamflow trends in the Upper Colorado River Basin by the U.S. <br />Geological Survey was initiated in 1997. This study consists of a small-scale study and a <br />large-scale study. The small-scale study examins changes in salt loads in four streams draining <br />irrigated areas of the Grand Valley. Salt loads for periods before and after salinity-control <br />projects in each basin have been estimated. Results for the four Grand Valley sites 'will be <br />published in a USGS Fact Sheet in late 1997 or early 1998. <br /> <br />The large-scale study will examine trends in dissolved-solids loads and streamflow in the <br />Colorado and Green River Basins upstream from Lake Powell. Results of a trend study in 1996 <br />by the USGS indicated decreasing salinity at some sites in the Colorado River Basin upstream <br />from the Grand Valley. It si not known if the trends were specific to a few sites or whether <br />there are widspread salinity trends throughout the upper Colorado River Basin and in the Green <br />River Basin. Monthly and annual loads for about 60 stations have been computed and trend <br />analysis of the loads and streamflow is underway. <br /> <br />Utah <br /> <br />Irrigation Drainage and Selenium -- Middle Green River Basin <br /> <br />Detailed study of wildlife areas in the middle Green River Basin of Utah during 1986-1990 has <br />shown that the concentrations of selenium in water and biologic tissues were harmfull to wildlife <br />at the Stewart Lake Waterfowl Management Area, lower Ashley Creek, and the Ouray National <br />Wildlife Refuge. The sources of selenium at Stewart Lake is irrigation drainage from the Bureau <br />of Reclamation Jensen Unit, which drains sedimentary deposits of marine and nomnarine origin. <br />Currently, an Enviromnental Assissment is being prepared to address constructed remediation of <br />Stewart Lake. In 1997, high spring flows in Stewart Creek were routed through Stewart Lake to <br />provide additional dillution water and to remove sediments from the lake bottom. <br /> <br />A significant linear relation (R2 of 0.65) exists between concentrations of dissolved selenium <br />discharges to Ashley Creek and concentrations of dissolved solids, but no relation (R2 < 0.01) <br />exists between loads of selenium and loads of dissolved solids. This indicates that salinity <br />controls that are chosen only to treat large sources of salt may fail to control loads of selenium. <br /> <br />8 <br /> <br />~ <br /> <br />. ~.., L,. ..~ .~~"" <br />