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<br />CHAPTER 1 <br /> <br />INTRODUCTION <br /> <br />. <br /> <br />would convert all irrigated lands in the unit area to a low-pressure <br /> <br />o <br />~ <br />1- <br />o <br /> <br />sprinkler irrigation system. <br /> <br />A 5,990 horsepower (hp) pumping plant <br /> <br />would be required to provide the pressure needed to operate the system. <br /> <br />The distribution system would be through pipelines from a pumping plant <br /> <br />at Big Sandy Dam. <br /> <br />Either siderolls or center pivot systems would be <br /> <br />used on the irrigated lands. <br /> <br />This system was designed to use all the gravity pressure available, <br /> <br />and although it would not be enough to maintain the 20 to 30 pounds per <br /> <br />square inch (psi) required, it would reduce the pumping plant size. In <br /> <br />addition to the pumping plant at the Big Sandy Dam, four additional <br /> <br />lateral line booster pumps would be required to boost the pressure to <br /> <br />. <br /> <br />some high areas. Wildlife mitigation features would be included. <br /> <br />With conscientious management of the individual farm systems, irri- <br /> <br />gation efficiencies could increase from a present average of 39 percent <br /> <br />to 70 percent. <br /> <br />The SCS estimates that salt loading in the Colorado <br /> <br />River would be reduced by an average of 96,300 tons per year. <br /> <br />The SCS did not calculate a cost effectiveness for this alternative <br /> <br />similar to calculations as they are performed by Reclamation. It does <br /> <br />appear, however, that the alternative would have a favorable cost effec- <br /> <br />tiveness when compared to Reclamation plans on this and other salinity <br /> <br />units. <br /> <br />The SCS economic evaluation of the alternative indicates that <br /> <br />the local irrigators could not pay for any of the installation costs of <br /> <br />the sprinkler systems and could only pay for about 38 percent of the <br /> <br />. <br /> <br />annual operation, maintenance, and replacement (OM&R) costs. <br /> <br />As a <br /> <br />13 <br />