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Subtask 5 - Initial MODSIM Runs <br />The MODSIM model has been tested for functionality with respect to the major reservoir operations, <br />diversions, and exchanges in the Gunnison River basin. To the extent possible, the model was developed to <br />emulate the assumptions and results of the prior GUNMOD efforts, although a number of changes were <br />made to adjust for inconsistencies in the GUNMOD data and because the MODSIM model is structured to <br />be a generic model that can be readily adapted for ot her river basins. MODSIM runs were made for the <br />baseline scenario simulated by GUNMOD, a scenario that assumes strict administration of the modeled <br />water rights on the basis of decreed priorities. The model was also modified to run for the historical <br />scenario, referred to in the GUNMOD documentation as the "good neighbor" policy (Protocol 2). The good <br />neighbor policy relates primarily to the assumptions used to model the operation and diversions by the <br />Gunnison Tunnel, whereby the tunnel se nior direct flow right is assume d to be subordinated to all junior <br />water rights in the Gunnison River basin, except for the storage decrees for Blue Mesa Reservoir. For this <br />scenario, it is also assumed that th e senior direct flow wa ter rights of the Uncompa hgre Project would not be <br />exercised against junior rights on th e main stem of the Uncompahgre River. These policies have been <br />generally endorsed by the UVWUA, the owners of th e Gunnison Tunnel and Unco mpahgre Project rights. <br />Subtask 6 - MODSIM Calibration <br />After MODSIM was set up and tested for the "good neighbor" scenario believed to be generally <br />representative of historic conditions in the basin, the model was calibrated by comparing simulated model <br />output to historic recorded stream flow at selected USGS stream ga ges, diversions at key water right <br />structures, and end-of-month storage contents in key reservoirs. For this calibration process, modeled <br />streamflows were compared to historic flows at the following stream gages: <br />Uncompahgre River at Colona Uncompahgre River at Delta <br />Gunnison River at G unnisonGunnison River be low Gunnison Tunnel <br />North Fork of Gunnison at So mersetGunnison River at Delta <br />Gunnison River near Grand Junction <br />Modeled diversions were compared to the recorded hist oric diversions at the key structures listed below. <br />These structures were chosen because they generally represent key rights that are explicitly modeled in <br />MODSIM (and GUNMOD) rather than being included within an aggregated priority class. <br />Gunnison Tunnel (South Cana l)Fire Mountain Canal <br />Loutzenhizer DitchIronstone Ditch <br />Selig DitchNorth Delta Canal <br />Modeled end-of-month storage contents were compared to historic recorded contents for the following <br />reservoirs: <br />Blue Mesa ReservoirTaylor Park Reservoir <br />Ridgway ReservoirP aonia Reservoir <br />Calibration of the MODSIM model for the ?good nei ghbor? scenario, including gr aphical comparisons of <br />Mosaic <br />the model simulated flows versus hi storical flows, is shown in the on-line documentation and in <br />Task Memorandum 1.16-27, MODSIM Calibration. <br />4 <br />A 275 .01.09.95 1.15-26 Fosha <br />