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I I I I I I I I I I I I I I I I I I I Further analyses of daily flows indicated surplus flows are provided mainly by peak discharges. Daily surplus flows were found to vary between 0 and 2 or 3 times the monthly average. Therefore, depending on when the monthly average surplus had to be diverted, the average canal capacity had to be multiplied by a factor ranging between I and 3 to obtain an adequate canal design capacity. For the purpose of cost estimation, a factor of two was initially used to size the canal design capacity. During the operation studies, however, it was found that these values could be reduced somewhat before impacting on the irrigation firmness and reservoir size. This allows the selection of an optimal canal design capacity. The one exception in this optimal size selection was that the enlargement of Overland Ditch had to be limited to 40 cfs because of location constraints. The final capacities used in the anal ysis by alterna ti ve and feeder canal were: Surface Creek Feeder Canal (cfs) Leroux Creek Feeder Canal (cfs) Overland Ditch Enlargement (cfs) Alternative No. I Alternative No.2 Alternative No.3 200 160 120 40 80 40 A similar flow duration curve analysis was also done to determine the capacity of the Cedar edge canal to the Lower Surface Creek service area. Flow rates for this canal were relatively constant in any particular month. The design size of the delivery canal was determined to be approximately 150 cfs. 2. Upper Basin Diversions: Increased Return Flows In the proposed operation of the basin, water supplies from stream flows and from the Grand Mesa reservoirs were first allocated to the upper service area. Since the upper service area shortages were greatly reduced, the reusable return flows were proportionately increased. The remaining stream- flows, augmented by the increased return flows were then supplemented by water stored in the Cactus Park reservoir to meet the lower basin demands. V-8