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~ f-o.o. ~ c.o . . Slrml:\RY SIIF.n' C:l",'ln,i V:1l1,'\' IIlli t COl.)[",ldo RiverlT~-;$Tn"s;-li[~i[y C~'lltrol P(-llj~Ct Ard1 1982 P<]~e 1 of 2 . LOCATION closed surfac<! bas in wh ich h,15 ~nd groullrl-wRt~r h~cn ~'1l1ipped to monitor inf 10.....s and out flows. lOC.1tprl in wpsc-ce:ntral the Colora,lo Riv~r be- .Joo Mack, and includ02s city in western Colo- The Gr.ll1d Valley Unit is Colorado all)np, the r~ach of tween the towns of Palisade Grand Junction, the laq1.,>st rado. PLAN Studies for the overall Gr<lnd Valley Unit indicate that the salt loading of the Colorado River" in the Grand Valley could be reduced by about 410,000 tons annually by decreasing the amount of irrigation re- turn flows and conveyance system seepage moving through saline suhstrata and picking up salta. The reduction would result in a decrease in the salin- ity of the river at Imperial Dam of approximately 43 mg/L and would be accompl ished by a two-sef!;ment program conducted by the Bureau of Reclamation of the Department of the Interior and by the Soil Con- servation Service of the Department of Agriculture. A systems improvement study is bl2ing conducted by RecL'lmat ion to detennine whether lining and/or placing canals and laterals in pipe is a cost effective mcans to reduce seepage. On-rann im- provements, including upgrading irrigation systems through CClst assistance, improving irrigation man- agement, improving grazing lands And gC.Azing prac- tice~ on private rangeland and voluntary wildlife improvement measures, to reduce deep percolation from fann operations are being implemented and studied by thl2 Soil Conservation Service. wildlife meilsures consisting of watering ponds and acquisi- tion of land to canpellsate for wildlife habitat losses are under consideration by Congress. PURPOSE The Grand Valley Unit is a component of the Colo- rado River Basin Salinity Control Project and was authorized for construction by the Colorado River Basin Salinity Control Act of 1974 (Puhlic La", 93-320) . the purpose of the Grand Valley Unit is to reduce the salt loading to the Colorado River attributable to agricultural practices by improving the water del ivery system and installing on-farm improve- ments. The combination of these programs would re- duce the amount of ground I.,'ater allo"led to perco- late .into the underlying highly saline soils and . MancO's Shale Formation. It is thought that the estimated 780.000 tons of salt added to the river annually can be reduced as much liS 60 percent by the implement at ion of the above mellsures. The unit is being developed in stages to allow the Bureau of Reclamation to begin construction in a portion of tile valley where plans and designs .are complete, where sufficient data ace available to assess the impacls of the initial development t.ttile investigations and planning continue on the rest of the unit, and where environmental impacts will not he siguificant. Results from Stage Onc will be evaluated before deciding to proceed with construc- tion of the rest of the unit. To help determine these results, a study area encompassing a portion of Stage One has been identified. this area. known as the Reed Wash Study Area, is a hydrologically STATUS The definite plan report for Stage One t-,'ater Sys- terns Improvement Program was completed Bnd approv- ed. Preliminary environmental studies have been conducted on the unit, and a negative determination of environmental impact was made by the Region.:!l Director in June 1978, for Stage One. The Canmis- sioner concurred with the determination in July N. 'CIoLIClI'IIIL" C4N4l IICDLANOS $YSTCM ,.