Cherry Creek Valley Risk Assessment Final Report

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H~droLogic Technolog~ Fax:3D3-688-8698 JLln 18 '99 7:23 P.DS to meet approximately 78% of the average annual design demand with the balance of the water demand met by Denver basin aquifer water. Analysis of a downsized storage system indicates that the average annual yield of the project is decreased by 17% when the total storage capacity of the project is decreased to the anticipated configuration of the project. As shown on Figure 2, a decrease in the total storage capacity to 289 acre.feet decreases the yield by approximately 38 acre-feet to an average of 191 acre-feet per year. J 4.0 rI:! .... 3.S o ~ 3.0 ~ 2.5 ",,2.0 :sa .2 1.5 >< 11.0 60,s 20.0 .s 0 WABASH RESERVOIR COMPLEX YIELD I CAPACITY ANALYSIS . -;t-cf?t~f=tl~~~:~f-~l~ .-\.-- -- -. -1----1 ----'."1----1--,!-.-+--.- ;:~~l-r~f~~~;~-:.J- 100 200 300 Storage Capacity CAF) 400 500 Analysis of the incremental yield of each acre- foot of storage capacity in the Wabash Complex shows that the yield of the project is approximately 0.95 acre- foot per acre-foot if storage when total project storage equals 50 acre. feet. Incremental yields of the project decline significantly above 165 acre-feet of total stage capacity. Increases to the total storage capacity above Figure 3. IncremeDtal Yield Curve 400 acre-feet result in a negligible increase in the average annual yield. At a total storage capacity of 800 acre-feet, the average annual yield increases by only 12 acre-feet per year. In other words, a doubling of total storage capacity provides little increase in the supply of water available from the project. The major finding of this project is that the yield of the Wabash Complex is not significantly . increased when the storage capacity of the project is increased above the 419 acre-foot decreed capacity. A decrease in constructed storage capacity to between 165 acre-feet and 289 acre-feet can effectively meet project design supply requirements while reducing the cost of the project. -4-