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<br />....... <br />.-- <br />'- . <br />In <br /> <br />C which is effective in meeting the crop water requirements Is dependent on the total precipitation <br /> <br /> <br />amount and the consumptive use requirement. The difference between the gross consumptive <br /> <br />use requirement and effective precipitation Is net consumptive use which represents the <br /> <br />amount of water which must be supplied to the plant by irrigation. <br /> <br />Net consumptive use values were estimated for average, wet, and dry year conditions on a <br /> <br /> <br />monthly basis. Average total monthly precipitation was computed for each of the average, wet, <br /> <br /> <br />and dry year conditions using historic precipitation for the period 1951-1983 at Norwood, <br /> <br /> <br />Colorado. Individual years during the 33-year period were classified as average, wet, or dry so <br /> <br /> <br />that each category would have an equal number of years. Gross consumptive use, by crop and <br /> <br />location as previously determined, was used with the average total monthly precipitation values <br /> <br />described above to compute effective precipitation for the average, wet, and dry year conditions <br /> <br /> <br />using the procedure defined in the SCS publication "TR-21'. Effective precipitation was then <br /> <br />subtracted from gross consumptive use to obtain net crop consumptive use by crop and <br />location In the service area for each of the average, wet, and dry year conditions. Table 3 <br /> <br />contains the effective precipitation for the Norwood and Redvale areas by crop type. Table 4 <br /> <br />contains the estimated net crop consumptive use values for each crop and area. <br /> <br />The net crop consumptive use values by location for the average, wet, and dry year conditions <br /> <br />were used as Input to the demand operation model. Irrigation efficiency. conveyance losses, <br /> <br />and cropping pattern and acreage by parcel were combined with the net crop consumptive use <br /> <br /> <br />data by the model to get monthly at-reservoir demands, in acre-feet per month, by land parcel <br /> <br /> <br />for the period 1951-1983. Tables 5, 6, and 7 contain the estimated crop demands for each <br /> <br /> <br />parcel for the average, wet, and dry year conditions, respectively. The demand operation <br /> <br /> <br />model uses the inflows and storage capacity of the Gurley and Cone systems to estimate the <br /> <br /> <br />ability of these systems to meet irrigation requirements. This application of the historic <br /> <br /> <br />conditions data was useful in assessing the overall water supply capabilities of the system. <br /> <br />5 <br />