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Gilcrest/LaSalle Pilot Project <br />Hydrogeologic Characterization Report <br />INTRODUCTION <br />STUDY PURPOSE AND SCOPE <br />Landowners in the Gilcrest/LaSalle area (Figure 1) have reported high groundwater conditions <br />resulting in property damage. In response, the Colorado Water Conservation Board (CWCB) has <br />provided funding to the Colorado Division of Water Resources (DWR) to conduct the <br />Gilcrest/LaSalle Groundwater Pilot Project (Pilot Project), an independent analysis of the <br />groundwater hydrology (hydrogeology) in the area. The Pilot Project objective is to identify <br />relationships between the climate, geology, hydrology, and water management practices and <br />groundwater levels in the area. The full Gilcrest/LaSalle Pilot Project scope of work includes 11 tasks <br />and is presented in Appendix A. The Colorado Geological Survey (CGS) performed the study <br />presented herein to characterize the Pilot Project Study Area (Study Area) hydrogeology by <br />completing the following component tasks: <br />Task 1 — Acquire existing groundwater level data and identify existing wells suited for <br />monitoring <br />Task 2 — Identify groundwater level data gaps <br />Task 4 — Compile aquifer hydrologic property data <br />Task 5 — Characterize the hydrogeology of the alluvial aquifer within the study area <br />This report documents findings of the four tasks performed by the CGS. Tasks related to stream <br />flow, diversions, irrigation practices, and climate were performed by other entities. Geographic <br />Information System (GIS) deliverables including a geodatabase, GIS source files for all maps <br />presented, the lithologic database, and an electronic version of this report are in Appendix B, <br />groundwater time -series elevation maps in digital format are in Appendix C, historical hydrographs in <br />digital format are in Appendix D, a description of hydrograph tool development is included as <br />Appendix E, and time -series depth -to -groundwater maps in digital format are in Appendix F. A map <br />showing locations of major irrigation canals, drainage ditches, ponds, and recharge structures is <br />presented as Appendix G. All digital format deliverables are on a DVD in a pocket in the back of hard <br />copy versions of this report or can be accessed online via the CGS website at <br />http://coloradogeologicalsurvey.org/. <br />PREVIOUS WORK <br />The Study Area has been the subject of previous regional investigations, many of which have been <br />compiled, supplemented by field investigations, and converted to GIS datasets as part of the South <br />M <br />