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model pre-processor, StatePP. StatePP then combines this data to create a precipitation recharge estimate <br />for the ground water model. The following information is provided by StateDGL <br />• Area by land use and soil type in each model cell (example alfalfa 100 acres soil type A, <br />alfalfa 50 acres soil type B, native vegetation 50 acres soil type B) <br />• Climate stations, and associated weights, that represent precipitation to each model cell <br />(example station 0448 weight 0.5, station 1437 weight 0.5) <br />Comments and Concerns <br />During the scoping phase, it was anticipated that StateCU may need to be updated to insure the <br />precipitation recharge estimate is consistent with other estimates of precipitation use <br />(consumption by crops or native lands, loss, storage, runoff, etc). However, using the monthly <br />soil moisture balance approach recommended under this task prevents double accounting of the <br />precipitation with other uses. Also, because the recommended approach is dependent on soil <br />type, the precipitation recharge calculation becomes a spatial exercise and is appropriate to keep <br />outside of the StateCU model. <br />A portion of the precipitation that falls outside a ground water model often contributes to an <br />aquifer. This inflow to the ground water model is expected to be calculated by the SPDSS <br />ground water model contractor as a boundary inflow. <br />References <br />Greb, B.W. December 1980. Snowfall and its Potential Management in the Semiarid Central <br />Great Plains, Prepared for the U. S. Department of Agriculture. Agricultural Reviews and <br />Manuals, ARM-W-18. <br />United States Department of Agriculture, Soil Conservation Service. March 1985. National <br />Engineering Handbook, Section 4 -Hydrology. Robert E. Rallison, National Hydraulic <br />Engineer. <br />ASCE Manuals and Reports on Engineering Practice No. 70. 1990. Evapotranspiration and <br />Irrigation Water Requirements. Edited by M.E. Jensen, R.D. Burman, and R.G. Allen. <br />Task 64.doc 13 of 13 <br />