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<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />Addi ti onal reservoi r operati on studi es were developed for examl m ng the fi rm <br />yield associated with enlarging Peterson and Comanche Reservoirs. The yields <br />determi ned from those analyses were compared with the fi rm yiel d resulti ng <br />from rehabilitating the dams to restore full water management capability. <br />Only the added increment of firm yield, resulting from the transfer of the <br />Twi n Lakes water ri ght, is used in the subsequent economi c analysi s for <br />comparing the unit cost of water among the alternatives. <br /> <br />Twin Lakes Reservoi r is currently restri cted to zero storage. Rehabil itati on <br />of the dam, spillway, and outlet works will increase the capacity to 278 <br />acre-feet. With the necessary repair work completed, the expected annual firm <br />yield is also 278 acre-feet. Even for an enlarged dam and reservoir with a <br />capacity of 460 acre-feet, the firm yield is 454 acre-feet, with an average <br />carry-over of 6 acre-feet per year. Obviously, the water supply is extremely <br />reliable to attain such a high percentage of yield when compared with storage <br />volume. The contributions from the feeder canal, which diverts from an <br />unnamed tributary of the South Fork of the Cache 1 a Poudre, is primarily <br />responsible for the excellent supply. The results of the reservoir operation <br />studies are presented in Table IV.8. <br /> <br />I <br />I <br /> <br />Storage rights are administered by gage height, rather than the decreed <br />storage capacity. The storage ri ght for Twi n Lakes Reservoi r all ows fi 11 i ng <br />the conservation space to gage height 20 feet, with an allowed storage of 460 <br />acre-feet. The el evati on-capacity tabl e for the reservoi r i ndi cates only 301 <br />acre-feet of storage at this gage height. An additional water right <br />application will be filed with the State Engineer's Office to assure that the <br />full 460 acre-feet can be stored at this site. <br /> <br /> <br />The operati on stUdy for enl argi ng Comanche Reservoi r is shown on Tabl e IV. 9. <br />Storage capaci ti es for the current reservoi r under unrestri cted conditi ons, <br />and for the enl argement, were 2,630 acre-feet and 3,090 acre-feet, <br />respecti vely. Thi s corresponds with gage hei ghts 35 ft. and 39 ft. on the <br />reservoir el evati on versus capacity curves. The fi rm yi el d associ ated with <br />unrestricted operations of the present facility is 1,775 acre-feet per year. <br /> <br />-33- <br />