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<br />., ~.. . OJ,: :::. ~ , <br /> <br />O:O245~ <br /> <br />5, Regulate nonnative fish releases/escapement into the main river, floodplain, and tributaries. <br />6, Control problematic nonnative fishes as needed. <br />7. Minimize the risk of hazardous-materials spills in critical habitat. <br />8, Provide for the long-term management and protection of populations and their habitats <br />beyond delisting (i.e., conservation plans). <br /> <br />DESCRIPTION OF THE PROPOSED ACTION <br /> <br />Historic. Current and Proiected DeDletions <br /> <br />This plan includes management actions intended to satisfy, at least in part, the recovery goals by <br />reducing or removing threats to the four listed fish species that inhabit the Yampa River. These <br />management actions were developed by considering likely impacts due to current and anticipated <br />future depletions from the Yampa River and its tributaries through 2045. This section describes <br />current depletions (i.e., CRDSS average annual depletions as of 1998), as well as anticipated new <br />depletions due to direct flow diversions, small tributary reservoirs, modest expansions of existing <br />reservoirs, and/or increased use of existing, currently under-utilized reservoir capacity. The <br />assumptions used to develop these estimates are based on the best information available to date. <br /> <br />Although future depletions are quantified below by sector and geographic area, actual future <br />depletions may not be limited exclusively to those sectors/areas nor allocated to those sectors or <br />areas in the proportions described below. However, certain assumptions were made in order to <br />assess the impacts of potential depletions to the endangered fishes. This assessment will serve as the <br />basis for an intra-Service biological opinion on this management plan. If the assumptions upon <br />which the assessment is based should change subst;lJ1tially-for example, if average annual <br />depletions exceed the future increment defined herein or new projects are proposed whose impacts <br />were not fully evaluated-the Service may reinitiate intra-Service consultation and supplement or <br />amend its biological opinion. <br /> <br />Colorado Depletions <br /> <br />The Yampa River Basin in Colorado has nine reservoirs larger than 2,000 acre-feet (AF) active <br />storage, These reservoirs range in size from 2,250 to 30,000 AF, with a total active storage capacity <br />of 97,160 AF (Table 4), However, several include conservation pools and/or other accounts that <br />generally are not fully exercised (i.e., drained and refilled) each year (Boyle Engineering 1999). <br />Eight of these reservoirs are in the Upper Yampa Basin and one (Elkhead Reservoir) is in the Lower <br />Yampa Basin. <br /> <br />The Colorado River Decision Support System (CRDSS) was used to estimate depletions from the <br />Yampa River in Colorado during a 90-year period of record (October 1908-September 1998). On <br />this basis, historic annual depletions averaged about 103,845 acre-feet (AF) in Colorado. Based on <br />more recent water demands viewed in the same hydrologic context, current average depletions were <br />estimated to be about 125,271 AF per year (Table 5). Agriculture (irrigation), thermoelectric <br />generation (power), evaporation, and municipal and industrial (M&I) water users are the largest <br />consumers, M&l water use includes mining, potable water supply, commercial and industrial uses <br />(other than thermoelectric generation), livestock and snowmaking. <br /> <br />Management Plan for Endangered Fishes in the Yampa River Basin <br /> <br />18 <br />