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Effects on Aspinall Unit Purposes <br />General <br />The Aspinall Unit is operated to meet many purposes and provide a wide spectrum of benefits to <br />the public. On a highly visible level, the Unit provides reservoir and river recreation for over <br />1 million visitors annually. A Gold Medal tailwater fishery and unique river rafting opportunities <br />have developed under existing flow regimes. Less visible, but of significant importance, the Unit <br />provides hydropower to the southwest. Blue Mesa and Morrow Point are operated to instantly <br />meet peak power demands, while Crystal provides firm power supplies while stabilizing river <br />flows. Flood control is provided to the downstream cities of Delta and Grand Junction as well <br />as intervening railroads, highways, and farms and ranches. Water exchange agreement <br />opportunities are created that enhance the public uses of the Taylor River and Taylor Park <br />Reservoir. In addition, stored water is available for future use and Compact development in <br />Colorado. <br />These existing and future uses can be affected by changes in operations that attempt to meet the <br />desired NPS flows as discussed in the following sections. It must be noted that this is a very <br />preliminary analysis due to time and data constraints. Operating to meet the NPS desired flow <br />goals does not create additional water in the river on an annual basis; it redistributes flows, with <br />increased flows at one time of the year and decreased flows at another. The model runs indicate <br />that the desired NPS flow goals are not fully met in all years. In order to meet these goals, <br />impacts on many project purposes would be more severe than described below. <br />Hydropower <br />In November 2000, the Western Area Power Administration is scheduled to provide a more <br />detailed analysis of hydropower issues and impacts. The following is a preliminary analysis <br />prepared by Reclamation. <br />Under certain hydrologic conditions, the total amount of electricity produced in a given year will <br />be reduced when water flows through the outlet tubes and/or the spillway and thus bypasses the <br />power plant. Water that bypasses the power plant in the spring is water that might have <br />otherwise been stored and released later during the hot summer months when the demand for <br />power is high. An approximation of the amount of this foregone generation can be estimated by <br />considering the difference between the annual generation under the baseline condition and the <br />annual generation under a proposed scenario. The annual cost to replace this power is then <br />determined by multiplying this difference in generation by the estimated cost of replacement <br />power. The following table identifies the estimated cost of replacing power lost due to power <br />plant bypasses to produce spring peaks and summer flows that would not have occurred under <br />historic operations. The cost of replacement power is presented for a dry year (1991), a wet year <br />(1984), and an average year (1982) that considers almost 24 years of record. <br />The annual costs estimated in the following table may be an underestimation of the impacts to <br />hydropower generation. This underestimation of impacts can be attributed to not including such <br />cost factors as increased maintenance, the lack of an evaluation of power system operational . <br /> <br />5