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Figure 4 <br />Gaged and Simulated Average Streamflow -Dry Year (1977) <br />60000 <br />.-. 50000 <br />t <br />r <br />0 <br />~ 40000 <br />N <br />w <br />N <br />L <br />tUp 30000 <br />O <br />LL <br />~ 20000 <br />R <br />L <br />a ioooo <br />OCT NOV DEC JAN FEB MAR APR MAY JUN JUL AUG SEP <br />^Gaged OPrevious CRDSS DEnhanced <br />During the Previous CRDSS StateMod modeling efforts, the maximum efficiency for the Yampa <br />River basin was limited to be 60 percent. Therefore, 60 percent was used in the Enhanced <br />analysis. The StateCU analysis shows that about 20 percent of the structures represented in the <br />Yampa River Basin simulation have late irrigation season calculated efficiencies equal to the <br />maximum (60 percent). Amore detailed study of basin-wide conveyance and application <br />efficiencies may result in a lower maximum efficiency. A preliminary analysis showed that if <br />the basin-wide maximum efficiency was set to 55 percent instead of 60 percent, dry-year <br />simulated streamflows using variable efficiency and soil moisture accounting would more <br />closely represent measured streamflows. <br />Again, as the system is more accurately represented by using the variable efficiency approach <br />instead of average efficiencies, a more accurate understanding of maximum efficiencies, coupled <br />with a better understanding of return flow locations and distribution of gains to ungaged <br />tributaries, is necessary for improved calibration. <br />Wet-Year Stream~a~e Comparison <br />Both the Previous CRDSS and Enhanced simulations are good predictors of measured <br />streamflows during wet years, as shown in Figure 5 for the representative wet year 1984. <br />During wet years when more water is available for diversions, the efficiencies are generally <br />lower (i.e. less of the diverted water is actually required) and more water returns to the river. <br />Note that a change in the basin-wide maximum efficiency used for the simulation would not be <br />VariableEff Taskl-5 6 of 17 November 5, 2001 <br />