Boulder Canyon (Colorado River) steamboats as they passed over the dangerous rapids of Devil's Gate Canyon, during their high water runs to the mouth of the Virgin River at Rioville, Nevada. Boulder Canyon (Colorado River) Boulder Canyon, originally Devils Gate Canyon, is a canyon on the Colorado River, above Hoover Dam, now flooded by Lake Mead. It lies between Clark County, Nevada and Mohave County, Arizona. It heads at western end of the Virgin River Basin of Lake Mead, at about . Boulder Canyon divides the Black Mountains into the Black Mountains of Arizona, and the Black Mountains of Nevada. Its mouth is now
Risks to the Glen Canyon Dam Dam forming Lake Havasu, Palo Verde Dam, and other dams and reservoirs. Because Glen Canyon Dam is also the central element of the Colorado River Storage Project, a failure may, depending on the volumes of water released and the damage caused, limit or completely cut off water supply to residences or farmlands along the Colorado River, and even into southern California depending on damage to canal headworks. The failure of Glen Canyon Dam would also destroy up to 964 known archaeological sites, including 264 that it currently affects in the Grand Canyon. Risks to the Glen Canyon Dam Glen Canyon