Glen Canyon Dam is a concrete arch dam on the Colorado River in northern Arizona in the United States, just north of Page. The dam was built to provide hydroelectricity and flow regulation from the upper Colorado River Basin to the lower. Its reservoir is called Lake Powell, and is the second largest artificial lake in the country, extending upriver well into Utah. The dam is named for Glen Canyon, a colorful series of gorges, most of which now lies under the reservoir.
In the early 20th century, seven U.S. states and two Mexican states in the Colorado River basin divided the flow of the Colorado River among themselves. Unfortunately, annual flow variations meant that the states in the upper basin would not always be able to deliver the amount of water to the lower basin stipulated by these contracts. The U.S. Bureau of Reclamation proposed a solution that would involve building multiple dams in the upper basin to regulate the flow downstream. However, problems arose when Reclamation proposed to build dams in the federally protected Echo Park canyon in Utah. After a long legal battle with environmentalist organizations such as the Sierra Club, they settled for a high dam at Glen Canyon.
Construction of Glen Canyon Dam started in 1956 and was not finished until 1966. When the reservoir filled, the dam began to deliver a steady, regulated flow of water downstream and generate a cheap, plentiful supply of electricity. In 1983, major floods nearly led to the dam's collapse, but disaster was averted by a close margin. By taming floods and other factors that once characterized the Colorado, the dam has led to major physical and ecological changes in the lower river. Controversy continues over the effects both positive and negative of the dam, which has also been antagonized in many literary works. http://www.nps.gov/glca/index.htm