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<br />1 <br />1 <br />1 <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 />I <br />I <br /> <br />to store Twi n Lakes water to provi de an alternative to rehabil itati ng the <br />dam. .The water utilization analysis will examine the incremental yield <br />associated with transferring the Twin Lakes water right to either of these <br />sites. <br /> <br />Reservoi r i nfl ows for Comanche, Peterson lake, and Twi n lakes were estimated <br />for the 1950 to 1983 water years. Since streamflow records do not exist above <br />any of these reservoi rs, records from simil ar watersheds were correl ated with <br />long-term index stati ons and, if necessary, adjusted for drai nage area si ze; <br />Annual records were used because the reservoi rs fi 11 in the spri ng and make <br />deliveries in late sUl1l1ler. The stream gaging stations used in this study are <br />presented on Table IV.6. <br /> <br />The only gagi ng stati on on the Cache 1 a Poudre River, whi ch covers the enti re <br />period, is at the mouth of the canyon near Fort Collins. The gage on the <br />South Fork Cache 1 a Poudre River near Rusti c has streamflow records from <br />August 1956 through September 1979. These data sets were correlated with each <br />other to e~tend the records for the gage near Rustic. <br /> <br />The gaging station on Little Beaver Creek near Rustic has a drainage area of <br />12.3 square mil es--about the same as Comanche Reservoi r. Other watershed <br />characteristics, including topography and vegetative cover, were also <br />similar. This station was correlated with the Rustic gage on the South Fork <br />Cache la Poudre River to estimate annual inflows to Comanche Reservoir. <br /> <br />For Peterson Lake Reservoir, the streamflow records for Fall Creek near Rustic <br />were correlated wi th the South Fork Cache la Poudre Ri ver near Rusti c, to <br />extend the period of record. Since the drainage areas differed by a large <br />percentage, the streamflows were adjusted by the square root of the rati 0 of <br />their drainage areas--about 85 percent. The adjusted annual flows were used <br />as Peterson lake inflows. <br /> <br />The water supply for Twin Lakes is derived from its contributing drainage <br />area, as well as from a canal, which di verts water from a small, unnamed <br />tributary of Pennock Creek. The reservoir inflows from the natural drainage <br />area were assumed similar to those at the stream gaging station on little <br /> <br />-27- <br />