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<br />MR. NICK C. IOANNIDCS <br />January 15, 19B2 - 1423/9 <br />P"Ue Two <br /> <br />The aLudy period 1941 - 1977 ""cd in Lhia aLudy w"'; LHJucd on aimilar <br />period used by Lhe U.S. Bureau of Heclamation for Lhe operation study for <br />Narrows Project. This common period was selected on the basis that any <br />operation studies conducted for this analysis was to assume that Narrows <br />Project would be in place and opcratiunal. Thc Narrows operation study, <br />conducted by the U.S. Bureau of Ilcclamation, shows an average annual spills <br />of B7, 700 acre-feet for the 37-year period, Le., 1941 - 1977. Reservoir <br />spills occurred during 14-years out of the total of 37-years used in the <br />operation study. The magnitude of these spills ranged from a low of 9,BOO <br />acre-feet in 1959 to a high figure of 734,700 acre-feet in 1973. <br /> <br />The periods when calls in Water Division No. 1 did not affect the water <br />rights in the old Water District No. 6 were first identified and tabulated. <br />Also, periods specifically identified as no demand periods were identified <br />and tabulated. This information waS obtained from the compilation of the <br />river calls for the South Platte River Basin available from the Colorado <br />Division of Water Resources. Coupled with this data, the periods of historic <br />spills occurring at Narrows Damsite were also identified and tabulated. The <br />historic spill periods for Narrows were obtained from the U.S. Bureau of <br />Reclamation ~arrows Operation Study for the 1941 - 1977 period. It is <br />assumed in this study that periods when Narrows Project water rights are not <br />in priority are those when Narrows Keservoir is spilling. <br /> <br />The daily diversion records fo. the South Boulder Canyon Ditch and <br />Leyner-Cottonwood Ditch for the 1941 - 1977 period were secured from the <br />Colorado Division of Water Resources. This data was coded and inputed to <br />the computer program used in the simulation of Erie's raw water supply system. <br />Appropriate changes to the computer program were incorporated to account <br />for the periods when Keystone Reservoir can store water available under the <br />assumed river conditions. <br /> <br />Two separate operation studies, covering the 1941 - 1977 study period <br />were conducted. In both of these studies the Narrows Project was assumed to <br />be in place and operational. The basic difference between the two separate <br />upcruLiulI aLudles wus the lnclualoll or exclusion uf the Leyner-CotLonwood <br />Ditch Company shares currently owneO by the Town of Erie. A summary of the <br />results of the two separate analysis is presented in Table-I. <br /> <br />The results of the two operation studies shows that the proposed Keystone <br />Reservoir will store on the average an additional 161 acre-feet of water per <br />year. This water is captured during periods when Narrows Reservoir is spilling <br />and river calls in Water Division No. 1 do not affect the water rights in the <br />old Water District No.6. The periods when Narrows Reservoi. is spilling were <br />found to be the controlling periods in determining when wate. could be captured <br />by the proposed Keystone Reservoir. The results of the two separate computer <br />runs, in terms of additonal water captured, are very similar. The primary <br />reason for the similarity in result~ is that when Leyner-Cottonwood shares <br />are added to the study the water supply demand on the system is increased due <br />to increase in the availability of additional taps. Another factor contributing <br />