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Task 91-Map Wells, Irrigation Systems And Irrigation Service Areas <br />Objective: <br />Map irrigation distribution systems served by diversion structures with average annual diversions <br />of 1,000 of and greater and their associated irrigation service areas using (1) irrigated parcels and <br />other GIS coverages and (2) input from water commissioners, water managers and water users. <br />In addition, map wells with capacity of 50 gpm and greater and assign to specific irrigation <br />service areas. This task will utilize GIS data developed in Tasks 89, 90, 92 and 94. <br />Background: <br />During Phase 1 and Phase 2, the Contractor will map irrigation service areas for Districts 64, 1, <br />2, and 3. The remainder is expected to be completed under Phase 3. In these four districts are <br />located approximately 8700 of the total 12,000 wells with 50 gpm or greater capacity (Table B-6, <br />SPDSS Feasibility Study, Final Report, October 2001). These wells, which represent 77 percent <br />of the total flow from wells, will be matched with irrigated lands. In these same four districts are <br />a total of 152 structures with annual diversion of 1,000 of and greater (Table B-2, SPDSS <br />Feasibility Study, Final Report, October 2001). These structures divert 50 percent of the total <br />average diversions in the study area. Thus approximately 50 percent of the surface water <br />irrigated lands (via 152 structures) and 77 percent of the groundwater irrigation (by 8700 wells) <br />will be assigned under Phase 1 and 2. <br />Approach: <br />91.1 Well Tabulation and Preliminary Groundwater Service Areas. A tabulation of an <br />estimated 12,000 wells with water rights and/or well permits having a capacity of greater <br />than or equal to 50 gpm are expected to be developed by the Systems Integration contractor <br />using the methodology and model from the RGDSS. A complete description of this <br />methodology is described in "RGDSS Spatial System Integration, Task 2.4: Wellfile <br />Analysis-Tool Development" (obtained at http://cdss.state.co.us/). The irrigated land served <br />by an irrigation well will be determined using the closest parcel method developed in the <br />RGDSS described in the memorandum "RGDSS Spatial System Integration, Task 3.1: Data <br />Centered Groundwater Model" (obtained at http://cdss.state.co.us/). Initial location <br />information for each of these wells will be from legal descriptions and existing information <br />from HydroBase. Locations and irrigation service areas will be updated using more precise <br />and more recent information from water conservation districts (i.e. GASP), water users, and <br />the Division 1 program on well locations and updating (as described in Task 92). This <br />subtask will produce an intermediate result of well locations and service areas that will be <br />reviewed and refined during meetings and visits to water users and water commissioners, <br />described under Task 91.3 below. <br />91.2 Preliminary Irrigation Service Area Mapping and Initial Contacts. Preliminary <br />Irrigation service area will be identified and mapped using the irrigated field boundaries, <br />satellite images and orthophotos prepared under Tasks 90 and 89. In addition, the Contractor <br />will use GIS data available in the geodatabase described in Task 94 including small-scale <br />USGS hydrography maps, digital elevation models, digital raster files of 7.5-minute USGS <br />quadrangles, and other sources. Finally, the Contractor will use GIS coverages obtained from <br />either the USGS (NHD) or the Colorado Division of Wildlife, that contain vector data of <br />C:IDocuments and SettingslckFlMy DocumentslSection DISPDSSISpatia/.doc 9 <br />