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FINDING OF NO SIGNIFICANT IMPACT <br />Cooperative Agreement to Implement the Management <br />Plan for Endangered Fishes in the Yampa River Basin <br />The U.S. Fish and Wildlife Service proposes to enter into a cooperative agreement with the states <br />of Colorado and Wyoming for the purpose of implementing elements of the Management Plan for <br />Endangered Fishes in the Yampa River Basin (Yampa Plan; Roehm 2004). An Environmental <br />Assessment (EA) accompanies the Yampa Plan, which describes anticipated human water needs <br />during the next 40 years and prescribes a series of ineasures to minimize adverse impacts to four <br />listed fish species due to current and projected future water depletions from the Yampa River and its <br />tributaries. These fish species are the humpback chub (Gila cypha), bonytail (G. elegans), Colorado <br />pikeminnow (Ptychocheilus lucius) and razorback sucker (Xyrauchen texanus). <br />Encompassing roughly 8,000 square miles in northwest Colorado and south-central Wyoming, the <br />Yampa River Basin yields an average of about 1.7 million acre-feet (MAF) of water each year at its <br />confluence with the Green River. Stream flows generally peak between late April and mid-June, <br />predominantly during the last 3 weeks of May, as winter snowpack melts when temperatures begin <br />to rise in spring. Intra-annual flow variation is high, with peak flows typically two orders of <br />magnitude greater than base flows in an average year. Flows also vary between years, with almost a <br />nine-fold difference between the highest and lowest peak flows recorded at Deerlodge Park (1982— <br />2003). <br />Relative to yield, current in-basin active water storage (�50,000 AF) is minimal (�3% of yield). <br />Current depletions of roughly 168,000 AF in Colorado and Wyoming represent about 10 percent of <br />average yield. Therefore, the annual hydrograph of the Yampa River has changed very little since <br />before settlement. We anticipate that during the next 40 years, depletions will increase by about 30 <br />percent to 221,000 AF or 13 percent of average annual yield. The proposed action would increase <br />active storage 5,000-12,000 AF, or 0.3-0.7% of yield, by enlarging the existing Elkhead Reservoir. <br />Up to 7,000 AF of the proposed enlargement would be used to augment base flows July through <br />February to support populations of native endangered fish species during critically low stream-flow <br />conditions. The balance could be used to supply water for human needs. In addition to instream <br />flow augmentation, the proposed action would continue and expand ongoing management actions <br />to control populations of predatory and competitive nonnative fish species, considered to pose a <br />significant threat to endangered and other native fishes. Other measures include acquiring, restoring, <br />protecting and maintaining floodplain habitats as nurseries for endangered fishes in the Green River; <br />monitoring incidental take by agricultural and other large diversion works, and installing screens, if <br />necessary, on these diversions to reduce or eliminate take; providing for fish passage, if necessary, at <br />any new diversion structures for water developments that existed prior to the inception of the <br />Recovery Program in January 1988; and monitoring both native and nonnative fish populations and <br />their important habitats to ascertain if management actions are having the desired effect of <br />increasing endangered fish populations while reducing nonnative fish populations. <br />Finding of No Significant Impact <br />