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
Black Canyon Diversion Dam Black Canyon Diversion Dam Black Canyon Diversion Dam (National ID # ID00282) is a dam in Gem County, Idaho. The concrete dam was originally completed in 1924, then re-constructed between 1951 and 1955, by the United States Bureau of Reclamation. Its structure has a height of 183 feet, and a length of 1902 feet at its crest. It impounds the Payette River for the diversion of water into the Black Canyon and North Side Main irrigation canals, and the generation of about 2 megawatts of hydroelectric power, part of the Bureau's larger Boise Project. The dam is owned and operated