Cataract Canyon is a 46-mile-long (74 km) canyon of the Colorado River located within Canyonlands National Park and Glen Canyon National Recreation Area in southern Utah. It begins at Colorado's confluence with the Green River, and its downstream terminus is the confluence with the Dirty Devil River. The lower half of the canyon is submerged beneath Lake Powell when the lake is at its normal high water elevation of 3,700 feet (1,100 m).