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Section E.7 <br />TO: File <br />FROM: Meg Frantz and Rick Parsons <br />SUBJECT: Subtask 11.7 -Verify Diversion Estimates <br />Introduction <br />This memo describes the results of Subtask 11.7, Verify Diversion Estimates. The objective of <br />this task was as follows: <br />Use the enhanced demandts to estimate historical diversions for the San Juan <br />and Yampa basins for the Existing POR (1975-1991). Execute the Phase IIIa <br />model in baseflow generation mode using the estimated historical diversion <br />(*.ddh) file. Compare the baseflows at key stream gages to those generated in <br />Phase IIIa using actual diversion data, to verify that the selected approach to <br />filling in diversion records satisfies the data extension objectives. <br />Pursuant to Subtask 11.4, Prepare for PC-based Operation, Boyle completed this task using PC- <br />based StateMod software products (demandts V6.07 and V6.08, and StateMod V8.06) and <br />Microsoft Access versions of Hydrobase (one for each model). <br />In Subtask 11.5, Characterize Streamflow Data, key indicator gages were identified within each <br />of the West Slope basins. Wetness conditions (e.g. wet, dry, or average) were assigned to these <br />gages for each month of the Extended POR (1909-1996), based on the gaged flows. In Subtask <br />11.7, historical diversions for all structures were estimated, based on actual data and wetness <br />condition, and limited by the structure's cumulative decreed amount over time. <br />Approach <br />The approach used in Subtask 11.7 is equivalent for the San Juan and Yampa models: <br />1. Indicator gages were assigned to subareas of the basin. <br />2. Phase IIIa commands files were modified to develop estimated historical diversions <br />based on actual data. <br />3. StateMod was executed in baseflow generation mode using the Phase IIIa input files and <br />estimated historical diversions (*. ddh). <br />4. Baseflows created from estimated diversions were compared to Phase IIIa baseflows at <br />key stream gages. <br />Appendix E E-78 <br />