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-8- • Four reservoir sites, one for each draw, were selected for investigation as shown on Figures 3 through 5. The irrigable areas that could be served by the reservoirs were identified for each draw, as described above. The storage requirement was computed for each reservoir by multiplying the irrigable area below by the annual irrigation requirement and adding an allowance for evaporation, seepage and operational loss. Evaporation loss was based on an annual evaporation rate of 33 inches applied to the reservoir surface area at one-half the reservoir volume. This was taken from "Average Annual Lake Evaporation Map of Colorado" obtained from the State Engineer's Office. Seepage and operational losses were taken as ten percent of the reservoir capacity. Total dam height was based on storing the required volume, plus a five foot allowance for spillway operating head and freeboard. Since each dam exceeds ten feet in height, design parameters were • based on compliance with the State Engineer's criteria for dam construction. Table 4 summarizes the potential annual yield of the four reservoirs. Economic Analysis Four irrigation systems were developed which consist of reser- voirs, headgates and ditches. Construction costs were estimated for the systems including costs for the dams, ditches, headgates and crossing structures. These were then compared to the value of the crops produced on the irrigated area below the reservoirs to evaluate the economic feasibility. Unit costs used in the analysis are summarized on Table 5, and construction costs are summarized on Table 6. The principal cash crop for irrigated farming in North Park is pasture grass and hay. According to the 1979 Colorado Agricultural Statistics, published by the Colorado Department • of Agricultural, the value of hay produced in Colorado varied ~(~ Leonard Rice Consulting Water Engineers.lnc.