Aerial view of Lake Powell, near Page, Arizona. The lake is a reservoir created by the flooding of Glen Canyon by the Glen Canyon Dam on the Colorado River, which straddles the border between Arizona and Utah. It is a popular recreation and vacation spot; an estimated two million people visit it annually. Powell is the second-largest manmade reservoir by maximum water capacity in the United States behind Lake Mead, storing 24,322,000 acre-feet of water when full.