9570 - Laserfiche WebLink

Home Browse Search

quantified effect on Compact development. The State of Colorado should be given the opportunity to analyze model runs from a Compact development standpoint as soon as possible. Summary The model results show that NPS desired flows can partially be met; however, none of the model runs completely meet the desired flows. Sufficient time has not been available to review the factors that determine this; however, operational criteria entered in the model and existing physical outlet capacities at all three dams play a significant part. One example is the winter elevation target at Blue Mesa, established by prior Reclamation studies, which often prevents lowering releases to the 300 cfs minimum that would save water for a spring peak. This operational criteria is very important in preventing upstream ice flooding in Gunnison County. Another factor is criteria for Blue Mesa Reservoir that protect downstream areas from flooding. Impacts on Aspinall Unit purposes such as hydropower, downstream flood protection, recreation, and fish and wildlife would occur under the NPS desired flows and are summarized below. It must be noted that these impacts result from model runs that only partially meet the NPS desired flow goals; in most cases, fully meeting the goals could increase impacts. Hydropower - Impacts to hydropower generation at the Aspinall Unit were analyzed for the seven model runs. For each model run, impacts in a typical dry year, wet year and average year were studied. Replacement energy costs for NPS desired flows range from $5.3 million in an average year to $11.6 million in a wet year. Other cost factors, such as volatility of the power market and loss of peaking power revenues at Morrow Point and Blue Mesa during spill periods, have not been included in the analysis at this time. The Aspinall Unit's ability to provide emergency response during power system emergencies would be reduced. Operation and Maintenance - Costs and scheduling of operation and maintenance activities would increase due to more frequent use of bypass valves, spillway gates, spillways, and stilling basins. Additional costs for modifications would be incurred in order to ensure this equipment and these structures meet engineering requirements. This higher and more frequent use would also result in periods of time where river flows would be interrupted in order to adequately inspect and maintain the structures. Fish and Wildlife - At Blue Mesa Reservoir, any change in the reservoir operation can affect loss of fish through reservoir outlets, the thermal regime of the reservoir, and the overall reservoir productivity. It appears summer reservoir levels would decrease by an average of 2 to 3 feet under NPS desired flows, having a negative, but not quantified, effect on reservoir fisheries. In the Gunnison River below Crystal Dam, May peaks, with appropriate ramping, should not be detrimental to the trout fishery. The June peaks have more potential for damaging rainbow trout recruitment. NPS desired flows would increase the number of days flows are reduced to the minimum of 300 cfs from roughly 800 to 1,600 days during the 24-year study period (or from an average of 33 days per year to 66 days), thus having an adverse effect on the trout fishery. 14