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�1 <br />I modeled individually. These water rights are modeled as diversions, <br />consumptive use demands, and return flows. <br />IMost small (in terms of quantityj irrigation water rights and a few small <br />municipal and domestic rights are represented as aggregated depletions rather <br />Jthan as diversion and return flows (depletions are the difference between <br />diversions and return flows). This was done because the large number of <br />_� diversions in the Study Area dictated a simplified approach at this <br />preliminary level of study. These rights were aggregated by geographical <br />� location and by relative water rights priority. Four priority classes were <br />defined using the priorities of the major water rights to divide the smaller <br />I rights into the four classes. An agreement between the USBR and the CRWCD and <br />the file documents supporting the agreement obligates the USBR to allow <br />junior, in-basin, upstream appropriators the use of water in an amount not to <br />fexceed 60,000 af (U.S. Department of the Interior, 1984). This agreement is <br />commonly referred to as the "Curecanti Subordination." The geographical <br />� distribution of the 60,0�0 aP of depletions is as follows: 20,000 af in the <br />drainage between Crystal and Blue Mesa Reservoirs and 40,000 af above Blue <br />� Mesa Reservoir within the Gunnison River Basin. The current junior upstream <br />depletions are far less than these amounts. Issues surrounding the <br />implementation of the agreement and its admin.istration have not yet been fully <br />resolved. However, the issues do not affect the study's hydrologic modeling <br />of the agreement including the modeli�g of historic Aspinall Unit operations. <br />I <br />The direct-flow water rights for the Aspinall Unit were not modeled <br />Iindividually. In the past, there has been no need for full administration of <br />these direct-flow decrees against upstream junior in-basin appropriators <br />because of the "Curecanti Subordination." Therefore, only the Aspinall Unit <br />storage decrees were modeled so that the hydrologic modeling could be <br />calibrated with historic operations. If a situation arises in the future <br />Iwhere in-basin depletions junior to the Aspinall Unit water rights are greater <br />than 60,000 af or out-of-basin diversions are implemented, the USBR may <br />, require administration of both the direct-flow and storage decrees. This <br />study has not addressed specific impacts of such administration. The <br />3-3 <br />