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Uncompahgre Project canals in which the efficiency was assumed to be 60 percent (40 percent return flow), <br />presumably because of the interception and re-use of return flows by other project canals. For the <br />MODSIM model, the system efficiency adopted fo r the Uncompahgre Project canals was changed from 60 <br />percent to 45 percent during the calibration process. For most of the basin, the timing of return flows in <br />GUNMOD and MODSIM was assumed to be 40 percent in the initial time step, 30 percent in the second <br />month, 20 percent in the third month, and 10 percent in the fourth month. An exception to this pattern was <br />the pattern adopted for the irrigated areas higher in the basin, above Gunnison where it was 50 percent in the <br />initial time step, 30 percent in month 2, and 20 percen t in the third month. With few exceptions, the <br />locations of return flow accrual was ported directly from the GUNMOD model. <br />As part of this task, an analysis was performed to evaluate the timing of return flows using the generally <br />accepted Glover procedure, which takes into account the hydrogeologic characteristics of the subsurface <br />soils and the distance of the irrigated parcel fro m the stream. Although there is limited published data <br />available regarding the subsurface characteristics, the Gl over procedure was used to establish a set of three <br />timing patterns that are believed to be representative of most conditions that would be encountered in the <br />CRDSS river basins, based on an acceptable range of values for transmissivity (20 to 80 feet per day), and <br />distance of the parcel from the str eam (1,000 to 10,000 feet). In the anal ysis, a saturated depth of 70 feet <br />and a void ratio of 0.2 were assumed. It is also noted that the user of the Wat er Rights Planning Model can <br />also input their own timing pattern for return flows and override the recommended values. Task <br />Memorandum 1.15-17, Analysis of Irriga tion and Municipal Return Flows, describes the analysis and <br />presents the recommended timing patterns. <br />Subtask 11 - Reservoir Evaporation <br />Evaporation from reservoir water surface areas is a depletion modeled by both GUNMOD and MODSIM. <br />For the Gunnison River prototype, the time series fo r unit evaporation rates for each of the modeled <br />reservoirs was ported directly from GUNMOD (SEASONAL.TXT file). <br />For future CRDSS river basins, a DMI utility was developed to access climatic data from the CRDSS <br />database and compute a time series of net monthly rese rvoir evaporation. This utility is described in detail <br />in Task Memorandum 1.15-12, DMI to Estimate Monthly Net Reservoir Evaporation. <br />Subtask 12 - MODSIM Interface <br />The prototype MODSIM model for the Gunnison River basin incorpor ates the existing MODSIM GUI, <br />modified and enhanced to provide a greater level of user friendliness within the CRDSS framework. <br />During the development of the prot otype, a number of enhancements were made to the MODSIM interface <br />including: a zoom feature, text annotation, additional error checking, node and link search feature, and <br />status codes. <br />Subtask 13 - MODSIM/GUNMOD Comparisons <br />This activity is an extension of the work involved in the development of the MODSIM prototype (Subtask <br />4) and the initial test runs of MODSIM to emulat e the GUNMOD operations and results (Subtask 5). The <br />results of the MODSIM GUNMOD comparisons are described in Task Memorandum 1.15-28, Comparison <br />of MODSIM and GUNMOD Results. <br />7 <br />A 275 .01.09.95 1.15-26 Fosha <br />