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'?J> <;J~~ "'<,;.' '"'?> F}f~~ Barry D. Wirth (801) 524-5403 For Release July 27, 1989 BACKGROUND INFORMATION ON THE GLEN CANYON ENVIRONMENTAL STUDIES The past studies the Secretary of the Interior referred to are the Glen Canyon Environmental Studies (GCES ), begun in December 1982 under the direction of former Interior Secretary James Watt. They were to determine the short and long-term impacts of dam releases on the environment of Grand Canyon National Park. There were two objectives: 1) to quantitatively define the impacts of Glen Canyon Dam on the resources below the dam, and 2) to identify ways to mitigate the observed impacts within the present operating criteria of Glen Canyon Dam. The study decision followed significant public concern over plans to uprate the generators in the dam's powerplant. In 1988, following five years of field work, the first GCES report was released. There were six general conclusions reached in that report. The GeES determined that some aspects of the operation of Glen Canyon Dam do have substantial adverse effects on downstream environmental and recreational resources. It was determined that flood releases cause damage to beaches and terrestrial resources. Under operating criteria utilized prior to 1988, the GCES predicted flood releases would occur in about one of every four years. A flood release was defined as any release exceeding power plant capacity which is 31,500 cubic feet per second (cfs). The GCES determined that fluctuating releases primarily affect recreation and aquatic resources. The Study determined that modified operations could protect or enhance some resources. Finally, the study stated that the understanding of the relationships between dam operations and the downstream resources is not complete. On July 6, 1988, the Executive Review Committee (ERC) of the GeES released its review of the technical information and reports developed during the Studies and the analysis of the Study by the National Academy of Sciences. The ERC was comprised of agency representatives from Reclamation, the National Park Service, the U.S. Fish and Wildlife Service, U.S. Geological Survey, the Department of the Interior, and Western Area Power Administration. The ERC accepted the findings of the study, but stated that additional studies concerning the impact of low and fluctuating flows and an economic analysis of the impacts of change on power operations was needed. The ERC pointed out that the studies were conducted during years of record high run-off of the Colorado River and there was not an adequate opportunity to observe fluctuating flows. 1 '.: ,.,t , ..~; il ~ ~;. ~ .,'.~ .'."'- r. . (~ , ~i: ~<, :'-.:t' ~i ~~i~ .0. ~i ~ ".,