Controlled Flood
Can Large Releases of Water Restore Habitats in Grand Canyon?
River runners and other observers in the Grand Canyon of the Colorado River have noticed a decline in the number and size of sandbars used as campsites--a decline attributed to Glen Canyon Dam, which controls the flow of the Colorado through the canyon (see map).
Experimental Flow
The U.S. Bureau of Reclamation, which operates Glen Canyon Dam, released an unusually high flow of water during late March and early April of 1996 to see if it could rebuild camping beaches and restore other habitats that have deteriorated since the dam's completion in 1963. Another experimental flow was released on November 21, 2004.
The water in 1996 was released at a rate of 45,000 cubic feet per second (cfs) from March 26 to April 2, 1996. This discharge, considerably higher than the 33,200-cfs maximum that can flow through the power plant, was intended as a small analog of larger flooding that was common during spring snowmelts before the dam was built. In 2004, "the dam's bypass tubes were opened for 90 hours, beginning Nov. 21. The peak high flows were sustained for two and one-half days (60 hours) at about 41,000 cubic-feet-per-second." -USGS Water Resources of Arizona
Scientists from the Bureau of Reclamation, the USGS, and other Federal and State agencies and academic institutions are studying the effects of the test flow, which was expected to rebuild sandbars that provide campsites and clean silt out of backwater channels used by native fish.
Two USGS Studies of Sand Redistribution
Several scientists from the Western Coastal and Marine Geology team are studying the redistribution of sand by the controlled flood. Their results will be used to test the validity of theoretical models that USGS hydrologists have developed to predict what will happen to sediment in the river at different flow rates. These models may eventually be used by the Bureau of Reclamation to regulate the flow of water from Glen Canyon Dam.
A Multidisciplinary Effort
The controlled flood is one result of more than a decade's study of the effects of Glen Canyon Dam on the Grand Canyon ecosystem by a multidisciplinary team coordinated by the Bureau of Reclamation's Glen Canyon Environmental Studies.
If the controlled flood is judged successful, such short-duration, high-release flows will probably be incorporated into long-term plans for the operation of Glen Canyon Dam, as recommended in an environmental impact statement, "Operation of Glen Canyon Dam," released in March 1995 by the Bureau of Reclamation.
For more information, see
- Controlled-flood information and illustrated fact sheets at the U.S. Geological Survey's Water Resources of Arizona Web site: http://az.water.usgs.gov/flood2.html
- List of Publications by U.S. Geological Survey Staff Done as a Part of the Glen Canyon Environmental Studies: http://az.water.usgs.gov/gcbiblio.html
- US Bureau of Reclamation details about Glen Canyon Dam: http://www.usbr.gov/dataweb/dams/az10307.htm
- How U.S. Geological Survey Western Coastal and Marine Geology scientists are studying effects of the controlled flood
- See Suggestions for further reading for the sources of information on this page.
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