High Quality Content by WIKIPEDIA articles! Cataract Canyon is a 46-mile (74 km) long canyon of the Colorado River located within Canyonlands National Park and Glen Canyon National Recreation Area in Utah. It begins on the upstream end at the confluence with the Green River and ends at the confluence of 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)