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Colorado River Science Experiments
Southwest Region, November 21, 2004
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The Grand Canyon was very wet and very wild during a 60 hour period when water releases from Glen Canyon Dam peaked at 41,000 cubic feet per second, up from 8,000 cfs, starting November 21, 2004.

The extra-drenching was part of a science experiment to move sediment downriver and was well covered by the media. Local, national and international newspapers and television stations carried the story.

The Grand Canyon Monitoring and Research Center of the U.S. Geological Survey (USGS) collaborated with scientists and resource managers from the Arizona Department of Fish and Game (ADFG), the Fish and Wildlife Service, the National Park Service; Northern Arizona University and other cooperators to prepare a suite of scientific experiments designed to evaluate the effect of the experimental high flows on natural resources in and near the Colorado River in Grand Canyon National Park.

A major portion of the research is focused on the well-being of native fish. The humpback chub, an endangered species, is one of four remaining native fish in the Grand Canyon. USGS scientists will be monitoring how the high flow releases affect the survival of a population of young humpback chub in the Grand Canyon near the confluence of the Little Colorado River.

The results of the scientific experiments will be used to evaluate the use of high flows as a management action for the preservation and restoration of natural and cultural resources in the Colorado River corridor below Glen Canyon Dam. These experiments also will contribute substantially to an understanding of the effect of high flows on natural and cultural resources so that the relationship between the operations of the dam and the natural environment may be better understood.

The ecosystem surrounding the Colorado River below Glen Canyon Dam has been significantly altered since the dam was completed in 1963. Of particular concern is the reduced amount of sediment available for building beaches below the dam and the recovery of one of the river's indigenous fish species, the endangered humpback chub.

Beaches provide a foundation for terrestrial habitat adjacent to the river as well as a safe and comfortable resting place for the recreational rafters and hikers who camp on them. In addition, sediment is important for in-place preservation of archaeological sites and other cultural resources. Most sediment entering Grand Canyon National Park now arrives from the Paria River and upper Marble Canyon tributaries below the dam.

The scientific experiments focused on sediment, native fish, and food for aquatic animals. Research will be supported by pre- and post-release remote sensing to determine how the beaches and sediment in the system respond to the high flows. Aerial photography will be complemented by channel bed mapping and sediment classification using sophisticated multibeam sonar. Subsequent remote sensing efforts around Memorial Day, 2005, and 18 months post-flood will track changes in the system over time.

External Affairs in the Southwest Region assisted with the preparation of fact sheets and news releases.

Contact Info: Martin Valdez, 505-248-6599, martin_valdez@fws.gov



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