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No surface water inflows occur at the top of each of the river basins. Surface water supplies do <br />come in to the headwaters areas via transbasin imports. <br />• Imports <br />Average annual imports to the South Platte River basin from transmountain diversions out of the <br />Upper Colorado River, North Platte River, and Laramie River basins were identified in SPDSS <br />Task 4. The Task 4 values include all transmountain diversions available in the HydroBase <br />database over the 1950-2002 period. No structures are operated to bring imported water into the <br />North Platte River and Laramie River basins; therefore, the transbasin imports to the North Platte <br />River and Laramie River basins were estimated to be zero. <br />• Ground Water Inflows <br />The only ground water inflows to the South Platte River basin come from the High Plains area of <br />the Republican River basin within the state of Colorado. Ground water inflows in the South <br />Platte River water budget were based on the value published in the Bittinger et al. study (75 <br />kaf/yr). The ground water inflows to the North Platte River and Laramie River basins were <br />estimated to be zero based on engineering judgment and discussions with the Water <br />Commissioners and Division Engineers for those basins. <br />Ou bows <br />• Agricultural Consumptive Use <br />Agricultural consumptive use (CU) was estimated based on the following: <br />- Irrigated acreage and crop mixes identified in the preliminary (2001) SPDSS GIS <br />coverage of irrigated lands -South Platte River (SPR) -approximately 1 million acres; <br />Laramie River (LAR) -approximately 3,000 acres; North Platte River (NPR) - <br />approximately 93,000 acres. Note that these acreage values are different than those <br />presented in the SPDSS Feasibility Study and CWCB Fact Sheets: SPR - 1.1 million <br />acres; NPR, including LAR and Sand Creek - 120,900 acres. <br />- Average annual crop water requirements (1950-2002) developed via the Blaney-Griddle <br />method with the StateCU model based on climate data from the Greeley climate station <br />for the South Platte River basin analysis. Crop demands were calculated based on specific <br />crop mixes identified for the different water districts in the preliminary SPDSS GIS <br />coverage. For reference, the preliminary mix of irrigated crops identified for the entire <br />South Platte River basin includes the following crops: grain-9 percent, beans-3 percent, <br />corn-32 percent, beets-3 percent, alfalfa-32 percent, pasture grass-20 percent, vegetables-1 <br />percent, and orchard-less than 1 percent. Climate data from the Walden climate station <br />was used to develop Blaney-Griddle estimates of crop water requirements (pasture grass <br />only) for the North Platte River and Laramie River basin analyses. <br />- Estimates of supply-limited irrigation water requirements (80 percent of crop water <br />requirement) in the South Platte River basin and an assumed full water supply (100 <br />percent) for crops in the North Platte River and Laramie River basins based on <br />engineering judgment and previous water rights analyses. Note that these estimates of <br />supply-limited crop requirements are similar to those used in the Statewide Water Supply <br />Initiative (SWSI) effort for the South Platte River basin (approximately 86 percent). <br />• Municipal, Commercial, and Industrial (M&I) Consumptive Use <br />Task83 final.doc 4 of 15 Apri17, 2005 <br />