Colorado River — Grand Canyon

About

Through 226 miles of Grand Canyon National Park, the Colorado River drops from Lees Ferry to Lake Mead on flows averaging 12,000 CFS — all of it now regulated by Glen Canyon Dam upstream. The Havasupai, Hualapai, Navajo, Hopi, and Southern Paiute peoples continue to call this the Living Canyon, as they have since time immemorial. John Wesley Powell's 1869 expedition opened the canyon to the outside world, but Glen Canyon Dam fundamentally transformed the river's character — what was once a warm, silty torrent now runs cold and clear year-round. Congress established Grand Canyon National Park in 1919, and UNESCO designated it a World Heritage Site in 1979. The river runs Class I through V depending on the section, with optimal flows between 8,000 and 25,000 CFS. Commercial outfitters like OARS Grand Canyon, Arizona Raft Adventures, and Grand Canyon Expeditions guide most trips, though private permits are available after a 12-year wait as of 2024. USGS gauge 09380000 at Lees Ferry tracks the releases that determine daily conditions through Coconino and Mohave counties.