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<br />. <br /> <br />.: <br /> <br />. <br /> <br />j ("\{) i; <br />vv'-..l...: <br /> <br />CRAPrER 3 <br /> <br />W ATE R RES 0 U R C E S <br /> <br />SURFACE SUPPLY <br /> <br />The purpose of the surface \olater portion of the investigation <br />is to determine the period of study and the water supply available <br />to the project during that period. The water supply ana~sis <br />includes both ground water and surface sources. The surface supply <br />was examined to determine historic use and the storable surplus <br />that would be available for regulation by Narro\ols Reservoir. <br /> <br />The storable water supply available to Narrows Reservoir <br />was determined on a monthly basis for the period of study. This <br />storable surplus flo\ol was determined from a point flow analysis of <br />the river, based on historic conditions. The point flow analysis <br />utilized all available data pertaining to river flows, direct <br />flow and storage diversions, reservoir releases to the river, <br />and tributary inflo\ol. <br /> <br />Period of Study <br /> <br />There \olere two periods of severe drouth from 1910 through <br />1961. The time period of study analysis was based on a comparison <br />of the shortages that could be met \olith a reservoir having 375,000 <br />acre-feet capacity at the Narrows site during the drouth periods in <br />the 1930's and the 1950's. The analysis indicated that a 375,000 <br />acre-foot reservoir would control all storable flows during the <br />critical periods and would give a 100 percent supply to 19 percent <br />of the land in the 1950's and to 49 percent of the land in the 1930's. <br />It \olas concluded from this analysis that the drouth period in the <br />1950's was more critical; therefore, the 19l+7-1961 period was <br />selected for study. <br /> <br />Table 4 presents long-term,records of annual stream flow and <br />precipitation. An analysis of these data indicates that the averages <br />for the period 1947 through 1961 are representative of the long- <br />term average flow and precipitation. <br /> <br />Storable Flows <br /> <br />The computation of storable flows for Narrows Reservoir was <br />based on an historic analysis of South Platte River flows between <br />the Narrows Dam site and the .Julesburg gage. The minimu.'!\ flow in <br /> <br />19 <br />