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OJ0373 UPCO Final Report Executive Summary May 29, 2003 Page vi As shown on the table, most water providers have sufficient water supplies to cover the current levels of demand (see page viii ofthis Executive Summary for discussion of2002 drought impacts). However, under future conditions, nearly two-thirds of the providers are expected to have demands that exceed their current water rights and/or water availability. The largest shortages are predicted for the Fraser River upstream of Tabernash, the Blue River upstream of Dillon Reservoir, Snake River upstream of Dillon Reservoir and Tenmile Creek upstream of Dillon Reservoir. Even though the hydrologic model calculates volumes down to the acre-foot and flow rates to a fraction of a cubic foot per second, the numbers provided on the table above, and in the full report, should be considered as guidelines and not the exact value of the shortage or supply. It is most useful to consider the reported values as relatively "large" or "small" and use comparisons and common sense to get a feel for the size and likelihood of future supplies and shortages. IV. PACSM Analysis Results Grand County The analysis ofPACSM results was divided into sub-basins. Fraser River Basin above and below the Town of Fraser: Under the PACSM model, municipal and domestic water supplies were adequate for existing levels of water demand, but most water providers would experience shortages under future demand scenarios. Shortages would be most severe for the Grand County Water & Sanitation District, ranging from an annual minimum of616 acre-feet to a maximum of 1,903 acre- feet and averaging 996 acre-feet. These shortages would occur primarily in the fall and winter months as a result of lack of physical supply and Denver's upstream diversions and would coincide with periods when streamflow would be below the CWCB instream flows, fish minimum flows and wastewater treatment plant low-flows. Water quality impacts related to Berthoud Pass, though not specifically examined in this study, emerged as issues. This includes water quality impacts related to winter sanding operations on Berthoud Pass and the potential for an accident of a truck carrying hazardous materials on Berthoud Pass. The latter could significantly affect water supply in the upper part of the Fraser River, as most providers divert directly from the Fraser with no alternative sources of supply. Colorado River Basin above the Fraser River confluence: Municipal and domestic water supplies were adequate under both existing and future demands. Though Northern is required to bypass flows below Lake Granby to maintain minimum instream flow requirements, instream flows below Lake Granby will be below CWCB, fish minimum and fish optimum levels. However, due to data inadequacies, it is not clear exactly how often this would occur. The only time flows will be below CWCB levels is when inflows are less than the minimum flow. Lake levels in Lake Granby were not fully evaluated in the study but should be before entering the solutions phase as lake levels relate to marina operations.