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~;'i~ ~ti t,; .' .._ " _~ . Executive Summary ES-4 Uncompahgre Rivers to irrigate lands in Delta and Montrose Counties. Water diverted from the Gunnison River and Tunnel is delivered to the Uncompahgre through the South Canal and Cedar Creek. After entering the Uncompahgre River, Gunnison River flows are combined with Uncompahgre River flows and diverted into six major canal systems. Mean annual diversions from the Gunnison River are 368,750 acre-feet. . Alternative E-! (the Sponsors' preferred action). This is the alternative that was approved in the PElS, The hydropower facility would have a capacity of 950 cfs. Mean annual diversions from the Gunnison River are 654,910 acre-feet, an increase of 286,160 acre-feet. . Alternative E-2. All factors would be identical to those of Alternative E-l, except that the capacity of the AB Lateral Facility would be reduced to 850 cfs. Mean annual diversions from the Gunnison River are 633,900 acre-feet, an increase of 265,150 acre-feet. . Alternative E-3. All factors would be identical to those of Alternative E-l, except that the capacity of the AB Lateral Facility would be reduced to 750 cfs. Mean annual diversions from the Gunnison River are 610,000 acre-feet, an increase of 241,250 acre-feet. Major Environmental Impacts Reclamation evaluated the potential for impacts to local and regional environmental and socioeconomic resources associated with change from the PElS. Development of the proposed project would impact several resource categories, including: . Streamtlows - Flows in the Uncompahgre River would be substantially increased downstream of the proposed powerplant, while flows in the Gunnison River would be . reduced. . River Morphology - Increased flow in the Uncompahgre River is expected to increase bank erosion and channel instability. The average channel width could increase as much as 30 feet. Sponsors have proposed an extensive plan to mitigate impacts and to continue monitoring bank erosion after project operations begin. . Wetlands - Development of the project and bank stabilization program would result in direct and indirect impacts to riparian wetlands along the AB Lateral and Uncompahgre River. Acreage affected ranges between 36 and 57 acres, depending upon the alternative. Development of the project is also expected to increase wetlands along the Uncompahgre River, resulting in a net, long-term gain of between 54 and 91 acres. . Water Quality - Channel instability during the initial years of operation is expected to increase turbidity and suspended sediment. Over the life of the project, these parameters are expected to return to current levels. Inputs of saIt and selenium to the Uncompahgre and Gunnison Rivers are expected to decrease due to the lining of the AB Lateral, the method of operation of the project, and anticipated structural improvements to the UVRP financed with project revenues. -.' :-" - , AB Lateral Hydropower Project July 2000 <,-,