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SPDSS Memorandum <br />Final <br />To: Ray Alvarado and Ray Bennett <br />From: LRE -Bruce Rindahl, Erin Wilson, and Beorn Courtney <br />Subject: Task 53.3 -Assign Key Climate Information to Irrigated Acreage and Reservoirs <br />Date: September 1, 2005 (Revised February 1, 2006) <br />Introduction <br />This memorandum presents the general approach for the following Task 53 subtasks: <br />1. Assign key climate stations to geographic areas for the SPDSS modeling efforts. <br />2. Estimate average monthly reservoir evaporation rates for geographic areas. <br />Temperature and/or precipitation climate data will be used in the SPDSS in four model efforts: <br />• Consumptive Use (CU) Model <br />• Ground Water (GW) Model <br />• Surface Water (SW) Model <br />• Water Budget (WB) Model <br />Consumptive Use Model Monthly temperature and precipitation climate data will be <br />used to estimate historic crop consumptive use in the CU model throughout the South <br />Platte, North Platte and Laramie River Basins (SPDSS study area). Key climate stations <br />were selected and monthly data were filled under the SPDSS "Task 53.2 -Collect and <br />Fill Missing Monthly Climate Data." By assigning key climate stations to geographic <br />areas (irrigated lands) within the SPDSS study area, consumptive use can be estimated at <br />any location. <br />Ground Water Model Monthly precipitation data will be used to estimate recharge for <br />the GW model. As with the CU model efforts, by assigning key climate stations to <br />geographic areas (ground water model cells) within the GW model area, recharge from <br />precipitation can be estimated at any location. <br />Surface Water Model. Average annual precipitation data will be used in the baseflow <br />calculations in the SW model to distribute flow at gages to ungaged locations. The <br />average annual precipitation GIS coverage, developed by the Colorado Climate Center, <br />will be used to estimate average annual precipitation within a defined sub-basin. <br />Water Budget Model. Two water budgets will be developed to represent the SPDSS <br />area; a monthly water budget representing the ground water model area, and an average <br />annual water budget representing the entire South Platte drainage. For the monthly water <br />Page 1 of 11 <br />