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4. The resulting reservoir decreed volumes were then summed by Water District to yield <br />one aggregate decreed volume per district. <br />Surface area associated with the decreed volume was estimated based on an average <br />depth of 17 feet. This depth was determined through an analysis of key reservoirs <br />identified in SPDSS Task 5 that had volumes less than 10,000 acre-feet. Note that <br />although 10,000 acre-feet was the one of the criteria to determine "key" versus <br />aggregated reservoirs, 14 key reservoirs were under 10,000 feet and used to determine an <br />appropriate average depth. Surface areas for the 14 smaller "key" reservoirs were taken <br />from the GIS water body coverage. Volumes associated with the GIS surface areas were <br />determined from the Task 5 area/capacity curves. The average depth was calculated to be <br />17 feet. The average depth was fairly consistent between reservoirs -the "goodness of <br />fit" R~ value based on a linear regression between reservoir volume and capacity was <br />0.79 for the 14 reservoirs considered. <br />6. A list of gravel mine reservoirs, and their associated surface area, that were built prior to <br />1981 was obtained for each Water District from Dick Wolfe (State Engineers Office) and <br />added to the aggregate surface areas to account for reservoirs that would not otherwise be <br />accounted in a water rights search. <br />Table 2 lists the results of the surface area estimates by Water District using the Decree <br />Method. <br />Table 2 <br />Aggregate Reservoir Surface Area by Water District <br />Usin Decree Method <br /> <br /> <br />Water <br />District <br />Decreed <br />Volume <br />(AF) <br />Estimated <br />Surface Area <br />(Acres)i Pre-1981 <br /> <br />Gravel Pit <br />Surface Area <br />Acres <br />Total Surface <br />Area <br />Acres) <br />South Platte <br />1 52,110 3,065 11 3,076 <br />2 20,029 1,178 111 1,289 <br />3 76,954 4,527 373 4,900 <br />4 51,603 3,035 70 3,105 <br />5 32,933 1,937 126 2,063 <br />6 56,972 3,351 25 3,376 <br />7 41,865 2,463 4 2,467 <br />8 22,176 1,304 134 1,438 <br />9 11,287 664 0 664 <br />23 43,492 2,558 0 2,558 <br />48 12,016 707 0 707 <br />64 18,079 1,063 7 1,070 <br />80 6,640 391 0 391 <br />Total 446,156 26,244 861 27,105 <br />North Platte <br />47 75,152 4,421 0 4,421 <br />' Surface Area estimated based on 17 feet average depth. <br />Page 5 of 14 <br />