Glen Canyon Dam

IDENTIFICATION: Large hydroelectric dam built on the Colorado River in northeastern Arizona.

DATES: Construction begun in 1956; reservoir filled in 1983

Construction of the Glen Canyon Dam flooded the pristine, wild Glen Canyon and created Lake Powell. Downstream, the dam’s effects on water temperature and sediment load affected the ecology of the Grand Canyon over time. Flow regulation experiments begun during the late 1990s sought to reverse some of the dam’s adverse effects.

The US Congress authorized the building of the Glen Canyon Dam in 1956 to provide water storage by creating the second-largest human-made reservoir in the United States, Lake Powell. Construction of the began in 1956, and the lake reached its full mark in 1983. The dam and generate hydroelectric power, provide a recreation area, and decrease siltation in the downstream Lake Mead reservoir, which is formed by Hoover (Boulder) Dam. The combined storage behind the Glen Canyon and Hoover dams manages the flow of water in the Colorado River to California, Arizona, Nevada, and Mexico. Agriculture consumes approximately 85 percent of the Colorado River water, with most of the remainder going to urban areas in Southern California; Phoenix, Arizona; and Las Vegas, Nevada. Glen Canyon Dam, with power plants, cost $272 million to build. Although the plants were designed to generate up to 1,300 megawatts of electric power annually, environmental damage to the riparian (shoreline) downstream in the Grand Canyon proved too great at this rate of electricity production, and the government limited production to fewer than 800 megawatts annually.

When construction on the dam began, Glen Canyon was considered extremely remote and was rarely visited. The Sierra Club initially fought the project but agreed to end its in a compromise agreement with the US Bureau of Reclamation that stopped construction of two other dams in Utah. The environmental organization’s leaders soon regretted their decision when they learned of the spectacular beauty of Glen Canyon. Sierra Club executive director David Brower teamed with photographer Eliot Porter to create a beautifully illustrated book titled The Place No One Knew (1963), which featured photographs of Glen Canyon before the dam. This book launched a Sierra Club policy of publishing illustrated books on outstanding natural areas to try to ensure that Americans would sacrifice no other spectacular areas because they did not know of their beauty. In 1996 the Sierra Club called on the federal government to drain Lake Powell and abandon the dam.

Many people view the Glen Canyon Dam as an icon of environmental destruction. The central theme of Edward Abbey’s landmark novel on ecotage, The Monkey Wrench Gang (1975), involves plotting to destroy the dam. The radical preservationist group Earth First! leaped into national prominence during the early 1980s when members unfurled a 300-foot length of black plastic from the top of the dam that gave the appearance of a giant crack descending down the front of the structure. Brower suggested that the lake be drained but the dam left “as a tourist attraction, like the Pyramids, with passers-by wondering how humanity ever built it, and why.”

Impacts

The most obvious postdam change was the flooding of a spectacular canyon and its tributaries, along with the accompanying loss of hiking and river-running experiences. The entire ecosystem of the inundated area, 653 square kilometers (252 square miles), was destroyed and replaced with a lake community. The reservoir water altered the color of the adjacent red sandstone rocks, resulting in a prominent white “bathtub ring” along the shore most of the year.

The reservoir behind the Glen Canyon Dam caused several other changes. Because the reservoir is located in the desert, an estimated 74,000 hectare-meters (1 hectare of water, 1 meter deep) of water (600,000 acre-feet) are lost to evaporation each year. Annually, more than 43,000 hectare-meters (350,000 acre-feet) of water seep into the surrounding rock strata. The river loses approximately 8 percent of its volume in Lake Powell. An additional concern is the rate of siltation. Silt and sand carried by the Colorado River settle onto the reservoir floor, and more than 123,000 hectare-meters (1 million acre-feet) of water storage have been loss to siltation.

Dramatic changes to the downstream riparian in the Grand Canyon are less apparent. Prior to dam construction, muddy river temperatures seasonally ranged from 26 degrees Celsius (80 degrees Fahrenheit) to nearly freezing. The dam releases water from the depths of the reservoir, and the river below the dam is approximately 9 degrees Celsius (48 degrees Fahrenheit). This water is also more saline than it was before the dam was erected, as evaporation allows the natural salts in the water to become more concentrated. In addition, the river below the dam bears only 15 percent of the sediment and load that it used to carry when it ran free. These changes have affected the aquatic fauna and flora of the Grand Canyon’s Colorado River. Several species have become extinct, and many nonnative or previously sparse species have flourished.

Releasing water from the dam to meet hydroelectric needs eliminated large floods but caused a daily tide as more water was released during afternoon, high-power-demand times and less flowed through the dam during the low-demand nights. The resulting tide stressed aquatic organisms downstream and caused rapid beach and sandbar erosion. Lack of natural flooding prevented rebuilding of the beaches and sandbars. The rapid loss of sandy deposits along the river in the Grand Canyon brought about ecosystem changes and had negative impacts on the recreational experiences of customers of the multimillion-dollar rafting industry.

New Approaches

During the 1980s and 1990s, the US Department of the Interior undertook an extensive review of the impacts of the Glen Canyon Dam that resulted in an environmental impact study. The major outcome of the $70 million study was a revised approach to the way water was released from the dam. Extreme and rapid daily fluctuations in river level to meet power needs were eliminated. Also, in the spring of 1996 the dam released an experimental flood with a slow rise to modest flood levels, followed by a gradual lowering of the river. The was designed to scour the river channels and rebuild the beaches, as happens in a natural flood. This flow management measure succeeded in redistributing existing downstream without contributing significant quantities of new sediment, but its benefits proved to be short-term. Other controlled flood experiments conducted in 2004 and 2008 also yielded transient benefits.

During the late 1990s, serious discussion began regarding the Sierra Club’s call to decommission the dam, drain Lake Powell, and restore Glen Canyon. If such a plan were to be carried out, it would take the reservoir fifteen to twenty years to drain. According to an assessment issued in 2000 by the Glen Canyon Institute, the dam could continue to generate hydroelectric power for ten to fifteen years while the lake drained. Opponents of canyon restoration asserted that decommissioning the dam would be too detrimental to water supplies, power generation, recreation, local economies dependent on tourism and the hydroelectric industry, and the ecosystems that had developed in the decades since the dam was built.

By the 2020s, considerations regarding the dam largely revolved around the fact that both the Colorado River and the Glen Canyon Dam had been affected by a lingering and devastating drought that impacted the American Southwest in the 2010s and early 2020s. In February 2023, Lake Powell reached a record low of 3,522 feet. If the lake level fell below 3,490 feet, the only way to get water to those who rely on it would be through a series of steel pipes originally designed as a means to release excess water. However, in 2024, the US Bureau of Reclamation found that the pipes, known as the outlet works, had potential structural damage caused by the formation of high-velocity bubbles that could have eroded the pipes’ lining or negatively impacted their concrete or steel. While some officials weighed repair options, other stakeholders continued raising decommissioning arguments.        

Bibliography

Carothers, Steven W., and Bryan T. Brown. The Colorado River Through Grand Canyon: Natural History and Human Change. U of Arizona P, 1991.

Dunphey, Kyle. "Problems with Glen Canyon Dam Could Jeopardize Water Flowing to Western States." Stateline, 17 Apr. 2024, stateline.org/2024/04/17/problems-with-glen-canyon-dam-could-jeopardize-water-flowing-to-western-states/. Accessed 17 July 2024.

Farmer, Jared. Glen Canyon Dammed: Inventing Lake Powell and the Canyon Country. Tucson: University of Arizona Press, 1999.

Gloss, Steven P., Jeffrey E. Lovich, and Theodore S. Melis, editors. The State of the Colorado River Ecosystem in Grand Canyon: A Report of the Grand Canyon Monitoring and Research Center, 1991-2004. Reston, Va.: U.S. Geological Survey, 2005.

James, Ian. "As Colorado River Shrinks, California Farmers Urge 'One-Dam Solution.'" Los Angeles Times, 5 Sept. 2023, www.latimes.com/environment/story/2023-09-05/california-farmers-urge-one-dam-solution-for-colorado-river. Accessed 25 July 2024.

Lowry, William R. Dam Politics: Restoring America’s Rivers. Georgetown University Press, 2003.

McPhee, John. Encounters with the Archdruid. 1971. Reprint. Farrar, Straus and Giroux, 2000.

Martin, Russell. A Story That Stands Like a Dam: Glen Canyon and the Struggle for the Soul of the West. U of Utah P, 1999.

Parks, Timothy L. Glen Canyon Dam. Arcadia, 2004.

Porter, Eliot. The Place No One Knew: Glen Canyon on the Colorado. Edited by David Brower. Commemorative ed. Gibbs Smith, 2000.

Powell, James Lawrence. Dead Pool: Lake Powell, Global Warming, and the Future of Water in the West. U of California P, 2008.