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<br />-~..: <br /> <br />In carrying out the study, basic data was gathered from the USBR. United <br />States Geological Survey (USGS), Bureau of Land Management (BLM) , U.S. <br />Fish and Wildlife Service (USFWS), Wyoming Game and Fish Department <br />(WGFD) , Wyoming State Engineer's Office, Water Resource Research <br />Institute of Wyoming, and the Eden Valley Irrigation and Draina~e <br />District. SCS conducted special surveys and investigations to obtain <br />other necessary data for this study. These included discussions with <br />farmers to inventory present irrigation practices. stream and drainage <br />flow measurem~nts, and compiling data on the soils and geology of Eden <br />Valley. <br /> <br />~~;"j <br /> <br />~ <br /> <br />111 <br /> <br />Using this basic data and a data hase period of 1960 through 1977, it <br />was determined that the Big Sandy River contributed about 149,180 tons <br />of salt annually into the Green River and the Colorado River system. <br />Most of the salt is leached from the underlying Bridger and Green River <br />marine shale formations and carried to the Big Sandy River by <br />underground aquifers. Excessive irrigation on highly permeable soils <br />and irrigation delivery system seepage provide water for deep <br />percolation to the underground aquifers. Of the total Big Sandy River <br />salt output, it is estimated that through the base period of 1960-77 <br />return flows from the irrigation delivery system seepage and deep <br />percolation from onfarm irrigation practices contribute about <br />133,860 tons annually. Natural runoff, erosion, and seeps contributed <br />an additional 15,320 tons annually. <br /> <br />EIS Development <br /> <br />~: .:' <br /> <br />On May 17, 1977, USBR and the SCS published the Final Environmental <br />Statement for the Colorado River Water Quality Improvement Program. <br />Additional information now available from the SCS environmental <br />evaluation of USDA federally-assisted onfarm improvements (nonproject <br />action) underway indicates that implementation of various onfarm <br />irrigation water management practices in the Big Sandy River Unit will <br />cause significant adverse local impacts on the environment. As a <br />result, the SCS has prepared for the Big Sandy River Unit an EIS which <br />supplemented the Colorado River Water Quality Improvement Pro~ram Final <br />Environmental Statement. <br /> <br />Implementation Issue <br /> <br />The landowners are concerned about the salinity problems and want to <br />implement the Selected Plan in a timely manner beginning as soon as <br />possible. This will require close coordination between state and <br />federal agencies to help the landowners implement thts Selected Plan. <br /> <br />-, 1 ~ ;i <br />l,,; .1..0 <br /> <br />,,"" <br />'.-,r.) <br />~^' <br />~ <br /> <br />F-2 <br /> <br />~.;; <br />'">i' <br />.i-~ <br />