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<br />. <br /> <br />w <br />.... <br />VJ <br /> <br />"~ <br /> <br />. <br /> <br />. <br /> <br />CHAPTER I <br /> <br />INTROIlUCTION <br /> <br />To acco~plish salt reduction. a two-segment pro~r~m 1s heln~ con- <br />ducted by the Bureau of Reclamation anel the U.S. ~partment of Agricul- <br />ture, Soil Conservation Service (5C5). A water ~yste~ improvement ~eg- <br />meot is being directeo by Reclamation. ....hile :m on-farm improvements <br />portion. consisting of upgrading irrigAtion systems an~ t~provin~ irri- <br />gation management, is being conducted hy the SCS. <br /> <br />The Bureau of Recla~tlon progra~ is divided Into two sta~ps of de- <br />velopment. Stage One development, completed in 1983, involved concretE> <br />lining a 6.~-ml1e section of the federally constructed Government Hf.~h- <br />line Cao."11 and rehabilitating structures along that segment. Also, 11 <br />laterals which previously served the area under the lined canal sect inn <br />were consolidated into 12 laterals and placed i.n pipe sections. Other <br />measures included development of an interceptor ditch and four small <br />detention ponds, an enlargement of existing cro5s-drainag~ features, and <br />installation of a moss and debris removal structure. <br /> <br />Planning studies were completed on Stage Two of the unit in 1983. <br />The Draft Environmental Impact Statement was filed with the Environ- <br />mental Protect ion Agency in September 1985. The recommended plan would <br />provide for membrane lining three reaches of th", Government Hi~hll"f> <br />Canal totaling 38 miles and placing most of the unlined laterals tn the <br />vall~y in pipe, Implementation of the recommended plan would reriuce <br />salt loading to the Colorado River by 128,700 tons annually and ....ould <br />decrease the salinity of the river at Imperial Dam by 7,2 to 21.7 MR/L. <br /> <br />The SCS on-farm improvement program provides cost sharinlo!. techni- <br />cal assistance, and planning service for farmers to reduce deep percol~- <br />tion of irrigation water and seepa~e from farm ditches. Improvements <br />consist of lining some exist inK farm ditches and placing others in pipe, <br />installing water measurinR devices and flow control structures, lAnd. <br />levelin~, and i.mplementing more efficient irr1~Ation systems. The 5CS <br />estimates that the on-farm Improvements could result in a total reduc- <br />tion of approximately 130,000 tons annually in salt loadinR, II reduction <br />that could be expected to lower the salinity of the Colorado River at <br />Imperial Dam by 5.h to 17.2 mg/L. <br /> <br />, <br />