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<br />002121 <br /> <br />Lake Powell, which results in clear cold water with year round temperatures of 41 to 450 F. <br />The recreation, irrigation and hydropower benefits introduced to the Southwest by GCD are <br />extensive and continue to expand. <br /> <br />Since the damming of the river in 1963, there has been only one flow release which <br />approached average pre-dam spring floods. lri 1983, a combination of unanticipated <br />hydrologic events in the upper Colorado River Basin, combined with available storage space <br />inLake Powell, resulted in emergency spillway releases from GCD which reached 97,000 <br />cfs. Except for the 1983 event, releases over the last 32 years have ranged generally between <br />1,000 and 25,000 cfs, with flows averaging between 5,000 and 16,000 cfs since 1991. <br /> <br />At the same time, and as a result of the construction of GCD, the Colorado River <br />ecosystem below the dam differs significantly from its pre-dam natural character. lri addition, <br />GCD's highly variable flow releases from 1980 to 1991 caused additional concern over <br />resource degradation resulting from dam operations. lri 1991 flow criteria from GCD were <br />changed. The Secretary adopted interim operations criteria in October 1991, which narrowed <br />the range of flow operations to historical seasonal flows. Normally these flows do not exceed <br />25,000 cubic feet per second (cfs), and range most often between 5,000 and 16,000 cfs. <br /> <br />A NEED FOR SCIENCE <br /> <br />Responding to concerns that changes to the Colorado River ecosystem were resulting <br />from dam operations, the US Bureau of Reclamation (Reclamation) launched the Glen <br />Canyon Environmental Studies (GCES) program in 1982. The research program's first <br />. pfiase, 1982-1988, focused on developing baseline Tesource assessments of physical and <br />biotic resources. The second program phase, 1989-1996, expanded research programs in <br />native and nonnative fishes, hydrology and aquatic habitats, terrestrial flora and fauna, <br />cultural and ethnic resources, and social and economic impacts. Developing spatial and <br />temporal data using GIS has also been a critical part of the second phase. <br /> <br />By the late 1980s, sufficient knowledge had been developed to raise concerns that <br />downstream impacts were occurring, and that additional information needed to be developed <br />to quantify the effects and to develop management actions that could avoid and/or mitigate <br />the impacts. This collective information and other factors led the Secretary of the lriterior <br />(Secretary) to direct Reclamation to prepare an EIS on operation of GCD. The intent was to <br />evaluate alternative operation strategies. <br /> <br />lri October of 1992 the President signed into law the Reclamation Projects Act, Public <br />Law 102-575. Responding to continued concerns over potential impacts of GCD operations <br />on downstream resources, Congress included in the Reclamation Projects Act Title 18, the <br />Grand Canyon Protection Act (GCPA). The GCPA directs the Secretary to operate GCD: <br /> <br />2 <br />