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Surface Water Modeling Effort <br />- Historic irrigation water requirements <br />- Historic ground water pumping <br />- Average monthly ditch system and well pumping efficiencies <br />Ground Water Modeling Effort <br />- Historic ground water pumping <br />- Ditch system conveyance losses <br />- Surface water and ground water application losses <br />The RGDSS surface water model planning scenario includes diversions from Costilla <br />Creek that irrigate lands in New Mexico. The consumptive use for these seven structures <br />was not included in the historic consumptive use analysis for the Rio Grande Basin in <br />Colorado. A separate consumptive use analysis, defined by the scenario response file <br />rgall_2004.rcu, was used that includes these New Mexico structures in the development <br />of consumptive use information for the surface water modeling effort. Only the input <br />structure file (rgall_2004.str) that defines the structures used in the analysis is different <br />from the basin historic consumptive use analysis. <br />The RGDSS ground water model covers the area overlying the aquifer systems in the San <br />Luis Valley. A subset of the basin historic consumptive use analysis was developed for <br />the RGDSS ground water modeling effort. This analysis, defined by the scenario <br />response file rgGW_2004.rcu, only includes consumptive use on lands within the <br />ground water model area. Only the input structure file (rgGW_2004.str) that defines the <br />structures used in the analysis is difference from the basin historic consumptive use <br />analysis. <br />2.3 Supporting Subtasks <br />The following subtasks were performed under the Consumptive Use and Water Budget <br />Component to determine monthly crop consumptive use in the Rio Grande Basin for the <br />period 1950 through 2002: <br />Annual Irrigation Parameter Time Series Generation. Historic irrigated acreage was <br />estimated based on the 1998 Irrigated Lands Assessment using historic County <br />Agricultural Statistics. The historic percent of acreage with access to ground water <br />supply, and the associated pumping capacity, was estimated based on well permit and <br />well right information. The historic acreage with sprinkler application was estimated <br />based on sprinkler mapping developed for the Rio Grande Water Conservation <br />District. The approach and results are provided in a memorandum attached as <br />Appendix A. <br />Estimate Ditch System Efficiencies. Conveyance efficiencies were estimated for ten <br />large ditches and the remaining smaller ditches based on water user interviews and <br />previous studies. Maximum sprinkler and flood application efficiencies were <br />estimated based on knowledge of irrigation practices in the basin. The approach and <br />results are provided in a memorandum attached as Appendix B. <br />cureport_6-2004.doc 10 of 48 June, 2004 <br />