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CRDSS <br />TASK MEMORANDUM 2.09-08 <br />Crop Consumptive Use Estimates for the San Juan, Dolores, and San Miguel River Basins for <br />calendar years 1985-1990. <br />1.0 ISSUE <br />This task memorandum describes the calculation of crop consumptive use (CU) for the San Juan, <br />Dolores, and San Miguel River Basins. The calculation of CU for the basin is based on a pro-ration of <br />the CU for a portion of the basin (areas associated with diversion structures being modeled) to the <br />irrigated area of the full basin obtained from a GIS. <br />2.0 DISCUSSION <br />Crop consumptive use has been estimated for selected structures in the San Juan, Dolores, and San <br />Miguel River Basins through the use of the CRDSS-CU model. The CRDSS-CU model calculates <br />irrigation water requirements which are provided to STATEMOD. STATEMOD imposes the irrigation <br />water requirements on a historic hydrology to estimate the water supply available for each structure. The <br />CRDSS-CU model then uses the water supply provided by STATEMOD to calculate the CU for each <br />diversion structure. The process is described by the following flowchart: <br />demand_cu UNIX script <br />List of Key Structures ---> CRDSS-CU Model ---> Demands for input to STATEMOD <br />STATEMOD Simulation ---> CRDSS-CU with Water Supply <br />To estimate CU for areas larger than the areas being served by the diversion structures being modeled, <br />the CU for modeled structures is pro-rated on the basis of the total area to modeled areas. <br />reportn utility program <br />CU and areas for modeled structures ---> GIS report of total areas ---> Pro-rated basin CU <br />2.1 Structures being Modeled <br />The diversion structures being modeled in STATEMOD for the San Juan, Dolores, and San Miguel River <br />Basins are provided to the CRDSS-CU model via the sanjuan.dds file, the header and a small portion of <br />the specific file used for this process is shown in Table 1. These structures are only a portion of the <br />diversion structures in the an Juan, Dolores, and San Miguel River Basins. The water supply information <br />for each structure is provided by STATEMOD in the sanjuan.xcu file, the header and a small portion of <br />this file is shown in Table 2. A total of 217 diversion structures are modeled in the San Juan, Dolores, <br />and San Miguel River Basins corresponding to a total irrigated area of 205,310 acres. <br />Of the 217 diversion structures being modeled, there are 23 structures for which GIS data is not available <br />with a total area of 66,696 acres, these structures are shown in Table 4. Structure 324675 was included in <br />1 <br />12/16/96 2.09-08 CSU/IDS <br />