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<br /> Crop irrigation <br /> Percentage requi rement <br /> Crop di stri buti on ( in) <br /> Corn 78 13.68 <br /> Alfalfa 14 22.47 <br />.. Irrigated pasture 3 17.28 <br /> Winter wheat 3 6.04 <br /> Sorghum 2 11.56 <br /> Weighted total 100 14.75 <br /> <br />The weighted crop irrigati on requirement for the present crop <br />distribution equals 14.75 inches or 1.22 acre-feet per acre. <br /> <br />Assuming the irrigation districts planted only sorghum (option I), <br />the crop irrigation requirements for the two districts would be reduced <br />by 3 inches per acre, when compared wi th the present crop i rri gati on <br />requirements. This amounts to a theoretical savings of 4,800 acre-feet <br />of water per year assuming 8,250 acres in the Frenchman Valley <br />Irrigation District, and 10,850 acres in the H&RW Irrigation District <br />were i rri gated. <br /> <br />The second option examined was to replace corn for grain, the most <br />predomi nant crop grown at 77 percent of the i rri gated acreages, wi th <br />sorghum. Thi s opti on wou1 d reduce the net i rri gati on requi rement, by <br />1.6 inches canpared to what currently exi sts on irrigated 1 ands. A <br />1.6 inch reduction in crop irrigation requirement results in a theore- <br />tical savings of 2,500 acre-feet of water. <br /> <br />The third option, that of replacing alfalfa with sorghum, is the <br />best of the three from the water savings standpoint. Alfalfa has <br />the highest consumptive use requirement of all the crops grown in <br />the two i rri gati on di stri cts. Repl aci ng the 14 percent crop distribu- <br />tion with sorghum would reduce the two irrigation districts' crop <br />irrigation requirements by 1.50 inches, theoretically saving 2,400 <br />acre-feet of water per year. This savings is approximately the same as <br />that saved by option number 2, but encompasses the conversion of fewer <br />, irrigated acres to sorghum. <br /> <br />From the theoretical water savings standpoint, crop conversions are <br />a logical way to reduce water usage and keep as many acres irriga- <br />ted as possible. Of course, factors other than water savings would be <br />considered by fanners contempl ati ng a change in crops grown, especially <br />the economi c consequences of such a change. It is un1 ike 1y a crop <br />conversion waul d occur if it waul d result in 1 ess net farm income. <br />Reducing the number' of acres being irrigated is another possibility, <br />but undesirable. The following section will discuss irrigation with <br />a limited water supply. <br /> <br />19 <br />