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<br /> <br />Low onfarm irrigation water efficiency (30-50%) is not generally <br />recognized by farmers as a problem. Irrigators use the amount of water they <br />have available, when it is available. The amount of labor use for irrigation <br />is perceived as being more important than the amount of ,water used. Onfarm <br />irrigation improvements are installed to reduce the labor needs. <br /> <br />A significant percent of irrigation system~ in the basin do not have <br />adequate water for the acres of cropland and pasture served. Crops that <br />receive only a partial water supply will not produce up to capability. <br />Therefore millions of dollars of crop production benefits are lost as a result <br />of water shortages in the basin! The following data of one selected system <br />helps illustrate this problem: 1/ <br /> <br />Selected Irrigation System - <br />Cropland served: <br /> <br />16,000 ac. alfalfa <br />23,892 ac. corn <br />10,000 ac. pasture <br />49,892 ac. Total <br /> <br />Water supply: <br />Diverted <br />Reservoir and purchased <br />Pumped <br /> <br />45,000 ac/ft <br />52,000 ac/ft <br />7,952 ac/ft <br />104,952 ac/ft <br /> <br />Estimated System Efficiency - 30.7 % <br />(Conveyance and on-farm) <br /> <br />Water Supply Available for Crop Consumptive Use - 32,218 ac/ft <br />(0.65 ac.ft/ac) <br /> <br />Irrigation Requirement of Crops (full supply) - 77,163 ac/ft <br />(1.55 ac.ft/ac) <br /> <br />Irrigation Water Shortage - 44,945 AF <br />(58%) <br /> <br />alfalfa <br />corn <br />pasture <br /> <br />Predicted yieldS <br />by the model for <br />"Future Without" <br />conditions <br />3.41 ton/ac <br />138.56 bu/ac <br />7.00 AUM <br /> <br />Possible with ful~ <br />water conditions 1/ <br /> <br />Crop Yields <br /> <br />5.50 ton/ac <br />140 bu/ac <br />7.5 AUM <br /> <br />Table A summarizes the system improvements believed by the irrigation <br />companies to be needed in the 23 systems studied. While the quantities may <br />vary for other systems in the basin, the same type of needs exist in most <br />systems within the basin. See individual reports for seriousness of problems <br />for each system. <br /> <br />1/ See Appendix J for a more complete analysis. <br />Z/ These yields could be further increased by applying management <br />practices not specifically related to water shortages. <br /> <br />- 6 - <br />