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<br />w <br /><:.:> <br />t..:. <br />w <br /> <br />Colorado <br /> <br />The cooperative effort between,the U.S. Geological Survey and the Bureau of Reclamation to, <br />maintain and update a salinity data base for the Colorado River B'asin was continued. Salinity , <br />loads for the 20 stations were updated for inclusion in the next biennial Progress report (number <br />18). In addition, the following projects are ongoing: <br /> <br />Irrigation Drainage Study, of the Lower Gunnison and Grand Valley Areas <br /> <br />A reconnaissance investigation of the Uncompahgre Project was done in 19,87c88 ana a report <br />published in 1991. That study focused on selenium problems at Sweitzer Lake. The <br />reconnaissance investigation also collected selenium and other trace-element data and salinity data <br />for the Uncompahgre and Gunnison Rivers. The results of the reconnaissance study indicated that <br />the Uncompahgre Project was a significant source of selenium. A detailed study was done in <br />1991-93 to determine source areas of.selenium and geochemical processes affecting selenium <br />concentrations in water and to determine if selenium was adverse affecting fish and migratory <br />birds. The Grand Valley was, a known source of salinity, and was suspected that it may be a <br />significant selenium source; therefore, the Grand Valley was included in the detailed study. , <br />Various surfacec and ground-water, mineralogic, geologic, and biological data were collected for <br />the detailed study. and the data were published in 1994. An interpretative report for the detailed <br />study was published in late 1996. <br /> <br />Based on results of the detailed study ,NIWQP decided that the Uncompahgre/Grand Valley area <br />should go into Phase 4 of the program, which is planning for remediation. Phase 4 was formally <br />initiated in FY -95 with the establishment of a Core Team to develop a plan for remediation. The <br />Core Team is headed by the Bureau of Reclamation and includes members of the U.S. Geological <br />Survey and U.S. Fish and Wildlife SerVice. In FY-96, the monitoring program will continued that <br />included collection of selenium and salinity data from selected tributary streams and washes and <br />mainstem rivers in the study area. One goal of Phase 4 is to detennine relations of selenium and <br />salinity in an effort to tie selenium remediation with salinity-control projects in the Lower <br />Gunnison Basin and Grand Valley. The Phase 4 team has been looking for a site in conjunction <br />with Natural Resource Conservation Service and Colorado State University Cooperative Extension ' <br />where the effects of on-farm sallnitycoritrol measures on selenium and ,salt loads could be' <br />documented. <br /> <br />Verification of Salinity-Control Projects in the Grand Valley Unit and Meeker Dome <br /> <br />In 1994 a study was initiated to determine trends in salinity in the Colorado River upstream (near <br />Cameo) and downstream from the Grand Valley (near the State line) and in the Gunnison River <br />near Grand Junction. Another aspect of this study was to verify that the well plugging done in <br />1981 at Meeker Dome was effective and that plugging has remained intact. The analysis was <br />completed in 1995 and a report was published in 1996. <br /> <br />9 <br /> <br />