Glen Canyon Dam
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Glen Canyon Dam is a dam on the Colorado River at Page, Arizona. The purpose of the dam was to provide water storage for the arid southwestern United States, and to generate electricity for the region's growing population. The dam has been controversial since its inception, because it caused the flooding of the scenic Glen Canyon and its tributaries to create a man-made reservoir, Lake Powell.
Its construction began in 1956. Although the dam was not dedicated until 1966, it was able to begin blocking the flow of the river in 1963.
The Sierra Club and other environmental organizations opposed the original plan for damming the Colorado River. When the plan was modified by the elimination of other proposed dams, however, the Sierra Club dropped its objection to the Glen Canyon Dam. Its then Executive Director, David R. Brower, later called this decision one of the biggest mistakes of his career:
- Glen Canyon died, and I was partly responsible for its needless death. Neither you nor I, nor anyone else, knew it well enough to insist that at all costs it should endure. When we began to find out it was too late.
(From The Place No One Knew, a Sierra Club book published in 1963)
Senator Barry Goldwater, who fought for funds to complete the dam, also later called its construction a mistake.
The dam has continued to attract opposition. In the 1975 novel The Monkey Wrench Gang, by Edward Abbey, the protagonists believe strongly that the dam has ruined the river. This book is considered a founding document of the ecoterrorism movement. Since 1996, the Sierra Club has called for increasing the release of water, so that a more natural flow of the river is restored and Lake Powell is gradually drained.
High volume flows are now periodically released to assist in re-arrangement of river beaches in the canyon, deemed necessary to prevent overgrowth of exotic plant species such as tamarisk.
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[edit] Description
The Glen Canyon Dam is a 710-foot-high structure which provides more storage capacity than all other storage features of the Colorado River Storage Project combined. The concrete arch dam has a crest length of 1,560 feet and contains 4,901,000 cubic yards of concrete. The dam is 25 feet wide at the crest and 300 feet wide at the maximum base. Its height above the Colorado River is 587 feet.
The Glen Canyon hydroelectric powerplant, at the toe of the dam, consists of eight 155,500-horsepower Francis turbines. Total nameplate generating capacity for the powerplant is 1,296,000 kilowatts. Eight penstocks through the dam convey water to the turbines.
[edit] Operations
The dam's hydrolectric plant generated 3,208,591,407 kilowatt-hours of electricity in 2005. Average residential per-capita electrical usage in Arizona in 2001 was 4,937 kilowatt-hours <ref>2001 Per Capita consumption of electricity in Arizona</ref>; per these statistics, the plant generates enough electricity to supply about 650,000 persons in the region with household power.
The states of California, Arizona, Nevada, and New Mexico receive about 8.2 million acre-feet of water each year from the Glen Canyon Dam. About 85% of the water goes to irrigation projects, and the rest is diverted to urban areas.<ref>Economic benefits of Glen Canyon Dam</ref>
[edit] Environmental impacts
Owing to this dam, there has not been the periodic flooding that would wash away and renew sand banks along the portion of the Colorado River that transits the Grand Canyon. Because of the stability of the sand banks, several non-native species of plants became established, adversely affecting the native wildlife.
An environmental impact statement was completed in 1995, which concluded that some effort needed to be made to re-enact flooding events on the river. Public hearings were held in Salt Lake City, Denver, Phoenix, Flagstaff, Los Angeles, San Francisco, and Washington, DC. More than 17,000 comments were received during the scoping period, reflecting national attention and the intense interest of people in the Western States. In accordance with the findings, a controlled flood was held in late March and early April of 1996.
The controlled floods appeared at first to have had a beneficial effect upon the downstream ecosystem. The results of an experimental flood in early 2005 were mixed. On a positive note, new beaches were built for the rafting industry and the natural sandbars that species in the area depend on were partially restored. On the other hand, silt was flushed into Lake Mead, reducing its capacity as a reservoir and recreation area, and at least half the population of an endangered fish species was lost during the flood, along with numerous trout and other gamefish. However, at least one endangered species, the willow flycatcher, has been finding a new home in many of the non-native plant species.
In 2006, the Bureau of Reclamation announced plans to develop another Environmental Impact Statement (EIS) on the implementation of a long-term experimental plan for operational activities at Glen Canyon Dam and other management actions on the Colorado River. The EIS continues efforts of the Glen Canyon Dam Adaptive Management Program created to protect resources downstream of Glen Canyon Dam, including the Grand Canyon, through adaptive management and experimentation.
This EIS process implements the provisions of the settlement agreement recently executed between the United States and the Center for Biological Diversity and other environmental groups in the Center for Biodiversity et al. v. Kempthorne litigation regarding the operation of Glen Canyon Dam. In conformance with the National Environmental Policy Act, this EIS effort will include public involvement and scoping and will consider a range of options and evaluate their ability to address scientific understanding and resource protection objectives.
[edit] References
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[edit] External links
- Glen Canyon Dam National Recreation Area
- Glen Canyon Dam page from the Bureau of Reclamation
- Images of Glen Canyon before it was flooded
- Article by David Brower on restoring Glen Canyon
- The Glen Canyon Institute
- 1995 Glen Canyon EIS
- New Environmental Impact Assessment of the Glen Canyon Dam (2006)
- Center for Biodiversity et al. vs the U.S. Department of the Interior regarding operations of Glen Canyon Dam
- Maps and aerial photos
- Street map from Google Maps or Yahoo! Maps
- Topographic map from TopoZone
- Aerial image or topographic map from TerraServer-USA
- Satellite image from Google Maps or Microsoft Virtual Earth
