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. Like all dams, Glen Canyon traps silt, but because the Colorado is an especially high-sediment river, the dam has posed even worse consequences for the river between it and Lake Mead (essentially, the Grand Canyon).
About 100 million tons of sediment are trapped behind the dam annually, equal to about 30,000 dump truck loads daily
Lake Powell is one of the most popular houseboating and water-skiing areas in the United States; the Glen Canyon National Recreation Area, which surrounds the reservoir, receives more than 1.9 million visitors annually. About 300,000 of these tourists travel via boat to Rainbow Bridge in Utah, a large natural arch once very hard to access, but now easily reachable because one of the arms of the reservoir extends under it