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February. Outside water use was estimated by subtracting the monthly in-house water use from the total <br />monthly municipal use. In-house consumptive use typically ranges from 5 to 10 percent of the demand; <br />for this analysis, a 10 percent in-house consumption was used. To estimate return flows from outside <br />irrigation, it was assumed that 20 percent of outside water use results in deep percolation to ground <br />water. To estimate the timing of lawn irrigation return flows, the ground water returns were lagged by 1 <br />month. <br />3.0 CONCLUSIONS AND RECOMMENDATIONS <br />The evaluation of irrigation and municipal return flow provides the following data for future application <br />in the CRDSS water rights planning model: (1) three recommended patterns for timing of irrigation <br />return flows, dependent upon the distance of the irrigated parcel from the stream and the subsurface <br />hydrogeology; (2) three options to estimate monthly streamflow depletion as a function of annual <br />irrigation consumptive use; and (3) default values for monthly municipal return flow factors. The timing <br />patterns described in this task memorandum should encompass the expected range of hydrogeologic <br />values for the river basins to be modeled in the CRDSS. Information from this study will provide <br />recommended guidelines related to the timing of irrigation and municipal return flows and irrigation <br />streamflow depletion that can be used to apply MODSIM to the CRDSS river basins. In all cases <br />however, the model user will have the flexibility to change or modify the patterns if better hydrogeologic <br />information is available. <br />5 <br />A275 01.09.95 1.15-17 Hyre, Fosha <br />