CRDSS_Task1_15-26_WaterRightsPlanningModelYear1Summary

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Subtask 8 - Natural Flow DMI Utilities GUNMOD and the MODSIM prototypes developed for th e Gunnison River basin both operate using a data set of stream flows representative of natural conditions. The term na tural flow is synonymous with virgin flow, defined as the flow in the ri ver that would have occurred in the absence of all activity by man, i.e., diversions, return flows, reservoir storage, and im port to and exports from the basin. With a model that starts with a natural flow data set, essentially all of the water rights and structures must be simulated in the model, either explicitly as a demand in the network or as part of an aggregated demand made up of a large number of individual rights of similar priority and lo cation. For the prototype model, natural flows at stream gages and natural inflows to the network structure were ported directly from the GUNMOD model (INFLOW.DBF files). The inflow data set used in GUNMOD was developed by the USBR and was adopted for use in the basin. For future CRDSS river basins, a DMI utility was de veloped that will produce natural streamflows and inflows in accordance with the same general procedur es utilized by the USBR. Natural flows are estimated by starting with recorded hi storical flow data and adjusting them for upstream man-made depletions. The DMI utilities developed for natural flow estimate s are summarized in Task Memorandum 1.15-15, DMI Utility to Estimate Natural Streamflow at USGS Gage Stations, and Task Memorandum 1.15-16, DMI Utility to Estimate Natural Streamflow and Inflow at Network Model Nodes. Subtask 9 - Water Rights Aggregation In order to account for all water rights in the basin, th e MODSIM prototype represents the majority of the water rights in the basin as "aggregated" water rights, which are grouped according to ten priority classes and by relative location in the basin. For the prototype , the aggregation of water rights (sorted by priority classes and by location) was ported directly from GUNMOD. The GUNMOD aggregations were not checked in detail to verify accuracy. However, there were a few instances in which the GUNMOD aggregations were modified, based on additional info rmation about water rights gained through interviews with the Division Engineer and water users. These modifications were principally in the Crystal Creek-Iron Creek-Smith Fork area. For future CRDSS river basins, a DMI utility was developed that will access the CRDSS water rights database, sort and group the water right structures according to decree amount and Administration Number, and convert the data to input formats required by the water rights planning model. Aggregated water rights will be assigned a weighted Administration Number for use in the model. This DMI utility is described in Task Memorandum 1.15-13, Water Rights DMI Utility. Subtask 10 - Return Flows MODSIM must account for the amount, timing, and locati on of return flows from irrigation in order to properly reflect the availability of water for diversi on by downstream structures. The amount of irrigation return flows is estimated by multiplying the diversion from the river by the factor of one minus the system efficiency. The timing of the return flows is prescr ibed by an input file indicating the amount of return flow that accrues to the river in the same time step a nd in succeeding time steps due to the lagged effect of groundwater return flows. It is also necessary to id entify the locations in the network at which irrigation return flows will occur. For the prototype model in the Gunnison River basin, the system efficiency values, return patterns, and location of returns (network nodes) were ported directly from GUNMOD (SEASONAL.TXT and CRAMOUT.TXT file). For most of the basin, system efficiencies were assumed to be 30 percent, (resulting in 70 percent return fl ow). An exception was the irrigation under the 6 A 275 .01.09.95 1.15-26 Fosha