Prehearing Statement of Colorado River Water Conservation District

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EXHI8IT B CRWCD'S PREHEARING STATEMENT (SILVERTHORNE RICD) Phase II Upper Colorado River Study Executive Summary i. lntroducfion The Upper Colorado River Basin Study (UPCO) was initiated in 1998 to identify and investigate water quantity and quality issues in the Study Area consisting of Grand and Summit Countiesl. The primary goal of Phase II of UPCO was to develop the information and analytical tools necessary to understand existing hydrology and water quality conditions in the study area and how increased water diversions may impact those conditions. This information was meant to support discussions and negotiations between the stakeholders as they seek solutions to current and future water supply, reservoir level, instream flow, and water quality issues. Participants in the study were Grand and Summit Counties, Colorado River Water Conservation District (River District), Middle Park Water Conservancy District (Middle Park), Northwest Colorado Council of Government's Water Quality and Quantity Committee (QQ), Northern Colorado Water Conservancy District (Northern), Denver Water (Denver) and Colorado Springs. The principal components of the Phase II study were: 1) compilation and analysis of water resources and water supply data for Summit and Grand Counties; 2) expansion of Denver's hydrologic and water rights model (Platte and Colorado Simulation Model, PACSM) to represent individual West Slope water supply systems; 3) development of a data management and display tool to support the analysis of impacts associated with existing and future water supply and demand scenarios; and, 4) identification of issues to be addressed in Phase III, the solutions phase, of the study. The study analyzed existing and future conditions based on the 1947-1991 hydrologic record. That is, the model used natural or "undepleted" stream flows for those years and accounted for the operation of water rights and demands to predict quantity and timing of water supplies, the depleted stream flows, and reservoir levels under various assumptions for the demands. The 1947-1991 period includes wet, dry and average years but does not include any years that are comparable to drought conditions- as severe as what occurred during 2002 when streamflows in many areas were the lowest ever recorded. Impacts created by the 2002 drought are discussed in more detail on page 8. The UPCO evaluations indicate a need for additional water supplies in Grand and Summit Counties for existing and future municipal demands as well as instream flows to support the area's recreational uses and maintain low-flow levels used to determine waste load allocations for wastewater treatment plants. Most pressing are additional supplies for the Fraser River, Upper Blue River (i.e., above Dillon Reservoir), the Snake River, I Phase l of UPCO was the development of the Scope of Work for Phase 11. Phase 111, to be initiated in mid-2003, involves a collaborative effort by the participating parties to seek solutions to the issues identified in the Phase 11 study report. Hydrosphere Resource Consultants