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<br />. <br /> <br />. <br />. <br /> <br />. <br /> <br />OG?'l?- 4 <br /> <br />efficiency improvements include the labor savings which result from modern delivery and <br />application systems, lower chemical (fertilizer and pesticide) and water costs when <br />application rates are reduced, fear of liability resulting from open and/or leaky ditches, <br />concern with local groundwater quality, increase available water supply to improve crop <br />yields, and availability of financial assistance through existing federal and state programs. <br /> <br />Specific practices employed to reduce irrigation diversions generally effect both non- <br />productive consumptive use and the return flow component of the irrigation water bu(iget. <br />Certain measures can have a larger impact on reducing incidental consumptive use than <br />others. Ditch evaporation can be reduced by combining parallel ditches and replacing <br />ditches with closed conduits, such as pipes. Reservoir operations can be modified to reduce <br />evaporation. Field evaporation can be reduced by delivery methods that get water into the <br />crop root zone faster than traditional flood irrigation methods, thereby reducing the amount <br />of water exposed to the atmosphere. Phreatophyte consumptive use can be reduced or <br />eliminated by clearing and cutting, or ditch lining which limits seepage into non-cropped <br />areas and eliminates seasonally high water tables. Irrigation management, which involves <br />the closer timing of irrigation deliveries to soil moisture content and crop needs, is also <br />capable of reducing field evaporation and phreatophyte growth. <br /> <br />Non-consumptive losses are usually reduced by ditch lining and on-farm practices which <br />reduce seepage and thereby deep percolation. Reuse of tail water from pump back pits will <br />reduce diversions and return flows. Generally any method capable of reducing consumptive <br />losses will also impact deep percolation and return flows to some extent. <br /> <br />The water budgets displayed in Appendix B represent the before and after conditions for <br />two areas in Utah where irrigation improvements are proposed under the federal salinity <br />control program. The improvements will mainly consist of replacing flood irrigation <br />practices with sprinkler systems. Some minor ditch lining will also be provided. These areas <br />historically have experienced short supplies due to junior water rights. Here, consumptive <br />use (but not irrigated acres) will actually increase after the improvements are installed. The <br />examples demonstrate the relative magnitude of the changes in non-productive cQnsumptive <br />use and return flows before and after a salinity project. Case III presents a calculated <br />irrigation budget for each area with crop consumptive use held constant. The Case III <br />budgets represent the situation that would occur if an area already had a sufficient or full <br />water supply based on. senior rights and did not experience shortfalls to existing irrigated <br />acreage. <br /> <br />Comparison of the figures reveals that non-productive consumptive use by phreatophytes <br />and evaporation can be reduced by as little as 1% up to 6% after a system is improved. <br />Deep percolation and tailwater that return to the stream can be reduced, allowing <br />reductions in diversions of up to 25 %. Irrigation efficiencies are improved from below 40% <br />to above 50%. In case II for the Uintah area, the amount of water deemed "conserved" or <br />"salvaged" under the definitions previously set forth is only 420 af/year, or a half percent of <br /> <br />7 <br /> <br />-, . r' " ,"" . '.~ <br />