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<br />percolation to the underground aquifers. Of the total Big Sandy River <br />salt output, it is estimated that through the base period of 1960-1977 <br />return flows from the irrigation delivery system seepage and deep <br />percolation from on-farm irrigation practices contribute about <br />133,860 tons annually. Natural runoff, erosion, and seeps contributed <br />an additional 15,320 tons annually. <br /> <br />PREVIOUS STUDIES AND RECENT HISTORY <br /> <br />The initial work for the Big Sandy River salinity study was done <br />from 1977 through 1979 with a USDA report being published November 1980. <br />Copies of this report are available for public reference and review at <br />the Rock Springs and Green River libraries and at the SCS office in Rock <br />Springs. The USDA report did not identify a viable alternative which <br />could be supported by the State of Wyoming, the SCS, and the irrigators <br />in the area. <br /> <br />Early in 1984, the State of Wyoming asked that the SCS evaluate an <br />additional alternative and update the landowner benefits that might be <br />derived from installation of a low pressure sprinkler irrigation system. <br />The economic evaluation and development of a low pressure sprinkler <br />irrigation plan was completed in 1984. This alternative was presented <br />to the State of Wyoming in November and at a public meeting December 17, <br />1984, of the Eden Valley Irrigation and Drainage District. Consensus <br />was favorable to the low pressure sprinkler alternative. The State of <br />Wyoming and Irrigation and Drainage District asked the SCS to prepare a <br />USDA Selected On-farm Low Pressure Sprinkler Plan. This report <br />addresses that alternative. The Low Pressure Sprinkler Alternative is <br />essentially the same as Alternative 3B as described in the 1980 USDA <br />report. Alternative 3B was a High Pressure Sprinkler Irrigation System <br />using on-farm pumping stations. The four account display of Alternative <br />3B as per Principles and Standards for Water Resource Projects is shown <br />in chapter 3, pages 3-5 and 3-6, and in appendix C, page C-3 of the 1980 <br />USDA report. <br /> <br />On February 27, 1986, a meeting was held with the representatives <br />of various State agencies to explain the contents of the USDA Selected <br />Salinity Control Plan. As a result of this meeting, the State has <br />indicated its continued support and willingness to participate in <br />finalization and implementation of the plan. On April 2, 1986, a public <br />informational meeting was held in Farson to explain in detail the USDA <br />Selected Plan and its impacts on the local irrigators and irrigation <br />district. Reaction of the local irrigators continues to be favorable <br />and the consensus of those attending is that the USDA Salinity Control <br />Plan on the Big Sandy River be finalized. <br /> <br />LOCATION <br /> <br />The Big Sandy River unit is located in southwestern Wyoming, <br />approximately 30 miles north of the town of Green River. The study area <br />encompasses parts of Sublette, Fremont, and Sweetwater Counties. The <br />watershed as outlined in Figure 1 is made up of two major drainages--t~e <br />Big Sandy River and Little Sandy Creek. The Big Sandy River i,uV ll, ~ 2 <br />left-bank tributary of the Green River. <br /> <br />2 <br />