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M&I CU was estimated based on recent (2000) census data for the basins, use rates of 230 <br />gallons per capita per day (SPR) and 280 gallons per capita per day (NPR and LAR) from the <br />February 2, 2004 Update on SWSI, and a CU rate of 40 percent based on previous water rights <br />analyses. <br />• Livestock Consumptive Use <br />Livestock CU was estimated based on recent (1997) county agricultural statistics, per-head use <br />rates of 10, 3, and 2 gallons per head per day for cattle, hogs, and sheep, respectively, and a 100 <br />percent CU rate. These per-head use rates are equivalent to the USBR values, which are <br />recommended for the livestock CU analyses in the SPDSS Feasibility Study Final Report <br />(October 2001). <br />• Reservoir Evaporation <br />The pan evaporation data identified in the SPDSS Feasibility Study for use in estimating <br />reservoir evaporation is incomplete and has a number of stations with very short periods of <br />record. For the initial water budgets, reservoir evaporation was estimated based on the total free <br />water surface area in the basin available from the GIS lake coverage on the cdss.state.co.us web <br />site, which includes actively-operated storage units, gravel pits, stock ponds, and other open <br />water surface areas. These basin area open water surface areas were multiplied by the gross <br />annual evaporation depth (per NOAA NWS-33) and a 70 percent fullness factor, which was used <br />to account for variable surface areas for actively-operated storage units and storage units <br />included in the GIS coverage that have depths shallower than the estimated average annual <br />evaporation depth. <br />• Native Vegetation Consumptive Use <br />The native vegetation CU term is the variable that is solved for (the `unknown') in the initial <br />water budget runs; therefore, no estimate of this component is input to the water budgets for the <br />SPDSS effort. The native vegetation CU values for the initial water budgets presented herein are <br />expected to be compared to other estimates developed in subsequent phases of the SPDSS effort. <br />• Surface Water Ou flows <br />At this time, the best estimates of surface water outflow from the three river basins are <br />determined based on the flow leaving Colorado recorded at the following stream gages: South <br />Platte River at Julesburg, CO; North Platte River near Northgate, CO; Laramie River near Jelm, <br />WY; and Sand Creek at CO-WY state line. The only stream gage maintained in the Laramie <br />River basin within the state of Colorado is the Laramie River near Glendevey, CO gage. The <br />Glendevey gage is located approximately in the middle of the basin within Colorado and does <br />not account for native inflows from McIntyre Creek, Nunn Creek, and other tributary inflows <br />downstream of Glendevey. The Jelm gage, on the other hand, is located just downstream of the <br />CO-WY state line and does not include any significant tributary inflows below the state line. The <br />Jelm gage was only active over the 1904-1963 period but is considered the best indicator of <br />average annual surface water outflows from the Laramie River basin within the state of <br />Colorado. As noted above, the Sand Creek surface water outflows are included in the Laramie <br />River basin water budget. The average surface water outflows for all gages but the Jelm gage <br />were identified in SPDSS Task 2. The Task 2 values include all recorded flows at the three <br />stream gages available in the HydroBase database over the 1950-2002 period. The annual <br />Task83 final.doc 5 of 15 Apri17, 2005 <br />