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1. Surface water is applied evenly to all acreage under a ditch system to meet the total <br />irrigation water requirement. <br />2. Ground water is pumped to meet any remaining irrigation water requirement on <br />sprinkler irrigated acreage identified as having a ground water source, up to the <br />maximum permitted or decreed capacity. Total (gross) pumping is estimated for <br />sprinkler acreage using a maximum efficiency of 80%. <br />3. Ground water is pumped to meet any remaining irrigation water requirement on flood <br />irrigated acreage identified as having a ground water source, up to the remaining <br />pumping volume. Total (gross) pumping is estimated for flood irrigated acreage using <br />a maximum efficiency of 60%. <br />The "maximize supply" approach uses ground water as the primary source on sprinklered <br />lands, surface water first on lands without a ground water supply, then on flood irrigated <br />lands with a ground water supply as follows: <br />1. Ground water is pumped to meet the irrigation water requirement on sprinkler <br />irrigated acreage identified as having a ground water source, up to the maximum <br />permitted or decreed capacity. Total (gross) pumping is estimated for sprinkler <br />acreage using a maximum efficiency of 80%. <br />2. Surface water is applied to meet the irrigation water requirement for acreage without <br />a ground water source at a maximum flood irrigation efficiency (60%). <br />3. Any remaining surface water is applied to meet the irrigation water requirement for <br />flood irrigated acreage identified as having a ground water source at a maximum <br />flood irrigation efficiency (60%). <br />4. Any remaining surface water goes to soil moisture storage or is available for return <br />flow. <br />5. Ground water is pumped to meet any remaining irrigation water requirement on flood <br />irrigated lands identified as having a ground water source, up to the remaining <br />pumping volume. Total (gross) pumping is estimated for flood irrigated acreage using <br />a maximum efficiency of 60%. <br />For the Rio Grande Basin historic consumptive use analysis, the "mutual" approach was <br />used to best represent irrigation practices for the majority of ditch systems. Based on <br />user information, the Rio Grande Canal, Farmers Union Canal, Prairie Ditch, and <br />Excelsior Ditch were modeled using the "maximize supply" option. <br />As described in Appendix A, HydroBase stores well water rights and permits and <br />associated location information, plus time series information defining irrigation methods <br />for each parcel. Efficiency numbers are derived, as described in Appendix B, and are not <br />stored in HydroBase. The time series file used in the historic consumptive use analysis <br />was created using wellproc.bas, apre-processor program described in Appendix A. <br />However, it is anticipated that StateDMI will be used to extract the time series <br />information from HydroBase, perform the necessary calculations, and develop the time <br />series input file for future model updates. <br />cureport_6-2004.doc 27 of 48 June, 2004 <br />