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<br />I <br />! I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />where <br />DR. = <br />1 <br />CIR. = <br />1 <br />Ef = <br />Es = <br />AREA = <br /> <br />minimum diversion requirement in acre-feet for month "i" <br />crop irrigation requirement in acre-feet for month "i" <br />field irrigation efficiency in percent <br />delivery system efficiency in percent <br />area size in acres <br /> <br />Based on the findings of the USBR, the average field irrigation efficiency was <br />estimated to be 50 percent, The delivery system efficiency was estimated to be 80 <br />percent due to a 20 percent loss of seepage in conveyance ditches and operation <br />losses, The combined effect of a 50 percent field irrigation efficiency and an 80 <br />percent delivery system results in a total irrigation diversion efficiency of lIO <br />percent. In other words, the irrigation diversion requirement equals 2.5 times the <br />calculated crop irrigation requirement, Minimum diversion requirements for the <br />study area are shown in Table II1-2. <br /> <br />The crop irrigation requirement was calculated as follows for each month within <br />the growing season: <br /> <br />CIRi <br />CWR. <br />1 <br /> <br />where <br /> <br />= CWRi - EPi <br />= Kc * PET; <br /> <br />CIR = crop irrigation requirement, in inches <br />C WR = crop water requirement, in inches <br />EP = effective precipitation, in inches <br />Kc = crop coefficient <br />PET = potential evapotranspiration <br /> <br />Crop irrigation requirements for the study are also presented in Table II1-2. PET <br />was calculated using the modified Jensen-Haise method, For each crop, the <br />monthly CWR value was determined by multiplying the monthly PET by the crop <br /> <br />III-Ill <br />