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<br />I)l'llll:l~ <br /> <br />Colorado's Net Irrigation Requirements for Agriculture, 1995 <br /> <br />Antony Frdllkl and Dr. David Carlson2. Colorado Dt:partmcnt of Agriculture <br />Dccemlxr 1999 <br /> <br />(he-nic\\' <br /> <br />This paper pro\ ides estimates ofnel irrigation n.-quiremcnts for each crop (induding pasturcland) by county in <br />Colorado for the year 1995. These estimates were generated from weather and crop water requirement data at.w <br />locations provided by the Natural Resources Conservation Servlcc.USDA (NRCS) and from harvested irrigated <br />cropland acreage published by the Colorado Agricultural Statistics Service and the Bureau afthe Census. <br /> <br />As defined by the NRCS. fief irriXr.Jlioll rt'(jlliremt!lII is the amount of irrigation \\atcr--exclusivc of precipitation. <br />soil moisture. or groundwater-that is required 10 meet potential crop consumptive use requirements. In this paper, <br />'net irrigation requirement' means the Of/.field requirement and excludes comeyancc losses and leaching <br />requiremcnts. Consequently, the estimates gi\en in this paper understate the amount of\\'ater needed by' agriculture <br />to produce irrigated crops at full yield potential levels. <br /> <br />For each crop in a given county. its net irrigation requirement (mcasured in acre. inches of water per acre) is <br />multiplied by the number of irrigated acres harvested of that crop in the givcn county for 1995. The resulting <br />!igure, divided by 12, is the number of acre. feet of irrigation water required at the field level to produce the <br />irrigated crop at its full yield potemial in the given county. lllese figures are then summcd for all crops and all <br />counties to give a total state.lcvel estimatc of 5.35 million acre-feel for 1995. <br /> <br />Actual cOllsumpti\'e usc of irrigation \\ater by Colorado crops cannot be directly inferred from these estimates of <br />net irrigation requirements because some fields are "'no\\n to rccei\'c less than a full water supply. Nevertheless, <br />the estimated state.lcvel net irrigation requirement of5.35 million acre-fect calculated in this paper is quite close to <br />irrigation consumptive use estimates developed by the U,S, Geological Survey of5,5 million acre. feet in 1995! <br /> <br />State.ll'nl Findings <br />Top fin Crops Top Five Counties <br />(Thousand acre-feet) (Thousand acre-feet) <br />Alfalfa lIay 1.661 Weld 570 <br />Com (grain) 1.196 Yuma 451 <br />Pasture/Other Land 901 Prowers 271 <br />Other Hay 582 ~'1organ 234 <br />Com (silac:e) 163 Kit Carson ,-- <br />_00 <br />Subtotal 4,503 Subtotal 1.759 <br />State.' Total 5.J50 Stale.' Total 5..350 <br /> <br />1995 Colorado l'Iet Irri~ation Requirements <br /> <br />TOTAL: 5.35 million acre. feel <br /> <br />OlI>erCrops <br />". <br /> <br />O\rIe<M.y <br />,,. <br /> <br /> <br />1 Research AssislaI1l. Colorado Department of Agricultur~, Resource '\nal)sis Section, (ffWl/: franl..lu nnmhacom <br />: Resour.:c AnaJ~sl. Colorado Depanmenl of Agriculture. ResoUTlX' Anal)sis Section. ("Im/: da'id.ca;.lson~ag.stalc...:o.us <br />J 1995 .....ater.u~eslimale from tho: U.S. Geological Sun C) Walcr.Use Web Site page (hUpJl.....aler.usgs.gO\iW8Iuselpdn995/pdf/irrigation.pdl). <br />Table 16. -Irrigation Waler Use by Stale. 1995:' <br />