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<br />. <br /> <br />O!W7GO <br /> <br />. <br /> <br />PART VI. mSTORIC IRRIGATION DEPLETION <br /> <br />. <br /> <br />The depletiDns tD the Florida River resulting from historic inigatiDn prac- <br /> <br /> <br />tices were estimated by analyzing the histDric ditch diversions, inigated acreage, <br /> <br /> <br />and the estimated inigatiDn requirement fDr the crops grDwn in the basin. FDr <br /> <br /> <br />the purposes of this analysis, depletiDn is defined as the reduction in stream- <br /> <br /> <br />flDW that occurs as a result Df inigatiDn practices, taking into aCCDunt stream <br /> <br /> <br />diversiDns, consumptive use of water, and return flDWS including the lagged <br /> <br /> <br />effects Df grDundwater return flDW tD the stream. Consumptive use is that <br /> <br /> <br />pDrtiDn of the inigatiDn water that is cDnsumed thrDugh evapDratiDn Dr crDp <br /> <br /> <br />evaPDtranspiratiDn. Irrigation efficiency is defined, fDr the PtV"Poses of this <br /> <br /> <br />analysis, as the percentage Df the water diverted frDm the stream that is CDn- <br /> <br /> <br />sumed. <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />Crop Consumptive Use <br /> <br /> <br />Based on field inspectiDns of the area and Dn interviews with the DivisiDn <br /> <br /> <br />Engineer and Water CommissiDner, it was determined that the principal crDps <br /> <br />grDwn in the FIDrida River basin include pasture grass-alfalfa (95%), CDrn (2.5%), <br /> <br /> <br />and wheat (2.5%). The cDnsumptive use Df irrigatiDn water was estimated using <br /> <br /> <br />the modified Blaney-Criddle procedure, calibrated to the area thrDugh use Df <br /> <br /> <br />data Dbtained frDm lysimeter studies cDnducted at the Navajo Indian IrrigatiDn <br /> <br /> <br />PrDject (NIIP). Monthly precipitatiDn data were Dbtained from the DurangD <br /> <br /> <br />weather statiDn (elev. 6550), where the mean annual precipitation is 18.61 inches. <br /> <br /> <br />Average mDnthly precipitation and mean monthly temperatures fDr the inigatiDn <br /> <br />. <br /> <br />. <br /> <br />season are summarized as fDllows: <br />. <br /> APR MAY JUN JUL AUG SEP OCT <br />Precipitation (in.) 1.20 1.02 0.63 1. 73 2.38 1.58 2.04 <br />Mean Temperature 45.1 52.9 60.2 67.5 66.0 58.6 48.8 <br /> <br />. <br /> <br />-11- <br /> <br />. <br /> <br />,.,k_"'~ <br />