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Colorado's Plan For Future Depletions January 12, 1998 <br />Documentation as Required by Cooperative Agreement, Page 6 <br />Milestones W6-1, W7-1, W8-1, and Tab 3B(I)E <br />4 Calculations <br />4.1 Gross M&I Water Use, AF/capita <br />A value of 0.25 acre feet per capita (223 gallons per capita per day) is assumed based on a <br />compilation of reported raw water uses and service axea populations for South Platte Basin <br />water providers. This is a generally accepted value for Colorado municipal water providers <br />with significant amounts of lawn irrigation within their service areas. <br />4.2 Average M&i consumptive use <br />A value of 36% is assumed to represent the average annual volumetric consumptive use for <br />municipal & industrial water use in a typical urban service area. This value is derived from <br />monthly municipal treated water delivery data and the following methodology. Indoor water <br />use for each month is calculated as the average of December, January and February treated <br />water delivery (all December through February delivery is considered to be for indoor use). <br />Outdoor water use for each of the months of March through November is calculated as the <br />delivery amount that is greater than the December through February average. Indoor use is <br />assumed to be 5% consumptive and outdoor use is assumed to be 80% consumptive. Each <br />month's indoor and outdoor uses are multiplied by these percentages, respectively, and the <br />results are summed. The resulting annual consumptive use is divided by the annual treated <br />water delivery. Using this methodology and reported monthly treated water use data for <br />individual water providers, a weighted average M&I consumptive use figure of 36% was <br />obtained. 4.3 Average irrigation consumptive use: <br /> <br />An average irrigation consumptive use value of 45% was assumed based on surveys and <br />research of irrigation practices within the South Platte Basin of Colorado conducted by the <br />Northern Colorado Water Conservancy District and Colorado State University. <br />4.4 Regional Supply Mix and Annual Accretive/Depletive Effects <br />The range of water supply and demand management options available to municipal water <br />providers is grouped into six water source categories: transbasin diversions, nontributary <br />(Denver Basin) groundwater, in-basin agricultural conversion, water conservation, water reuse <br />and native South Platte water development. The mix of future water supplies for each region is <br />specified by the user. <br />The annual accretive or depletive effect for each water source category is a function of the <br />source-specific use pattern and the method of calculating the accretions and depletions for that <br />source, as described below. As such, the annual accretive or depletive effect is a"signature" of <br />each source category and does not vary with changes in user input.