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<br />001996 <br /> <br />:.0 <br /> <br />The weather stations recommended by CRDSS (shown in Table 2 and 3) are used, The data sets are <br />prepared to support the input requirements for estimating evapotranspiration by the SCS Blaney- <br />Criddle method. The data set for Penman-Monteith calculations cannot be prepared mainly because <br />of a lack of representative daily weather data for the entire Dolores and San Juan River Basins, <br /> <br />Table 4 shows the annual irrigation water requirement (IWR) for ] 985-] 990 for the Dolores and San <br />Juan river basins as estimated by using the SCS Blaney-Criddle evapotranspiration estimation. The <br />6-year average annual IWR is 344,404 acre-ft. The peak IWR is in ]989 (4]6,524 acre-ft) while the <br />lowest IWR occurred in 1986 (275,407 acre-ft), Table 5 shows the 6-year average annual IWR by <br />subarea, The highest IWR by subarea, by county, and by HU is in Montezuma 14080002 in the San <br />Juan river basin (74,255 acre-ft), La Plata (134,424 acre-ft), and HUl4080101 (79,128 acre-ft), <br />respectively, <br /> <br />Table 6 shows the 6-year average annual IWR in terms of unit depth for each subarea, The average <br />value for the Dolores and San Juan river basins is ].45 feet. The highest per unit depth IWR by <br />subarea, by county, and by HU is in Mesa 14030004 (2.66 feet), and the smallest per unit depth IWR <br />by subarea is in Archuleta 14080102 (] foot). <br /> <br />3.0 CONCLUSIONSIRECOMMENDATIONS <br /> <br />The 6-year average IWR for the Dolores and San Juan river basins is estimated to be 344,404 acre-ft. <br />The water supply information should be considered directly when estimating the actual consumptive <br />use. The CRDSS consumptive use (CRDSS-CD) program has this capability. By linking CRDSS- <br />eu to the Water Resource Planning Model (STATEMOD), estimates of consumptive use are subject <br />to the actual availability of water supply. The results of this process are presented in Task <br />Memoranda 2.09-05 - 2.09-08. Other uses (non-irrigation CU) are presented in Task Memoranda <br />2.09-10 - 2,09-13 and total values for the entire Colorado River Basin are presented in Task <br />Memorandum 2.09-20. <br /> <br />Depending on the level of detail desired, several different data sets can be prepared for estimating <br />IWR in the Dolores and San Juan River basins, Smaller subareas may be chosen to increase the <br />representativeness of the consumptive use data. For example, the growing season of a particular crop <br />may not be uniform across a subarea defined by HU and county combination, thus, breaking the <br />subarea into smaller areas would allow assigning a more representative growing season for each <br />smaller area. Similarly, when the weather parameters in a HU-county subarea are derived by <br />weighting two or more weather stations, it may be better to break the subarea into smaller areas such <br />that each smaller area is associated with a single weather station. <br /> <br />4.0 OTHER ESTIMATES OF CONSUMPTIVE USE <br /> <br />The CRDSS-CU model incorporates an enhanced version of the SCS Blaney-Criddle methodology <br />which includes a monthly soil moisture budget. This allows soil (i,e., water holding capacity, and <br />AWe) and management (i.e., management allowed depletion, MAD) characteristics as well as winter <br />soil moisture carry-over to be incorporated in the estimation of IWR, Using the enhanced version of <br />the CU model, new estimates can be obtained. <br /> <br />11.26.96 <br /> <br />2 <br /> <br />V19-04IDSlCSU <br />