READ HERE: 40 million Americans in 7 states might have to move because their primary source for water is either from Lake Mead in southern Nevada or Lake Powell on the Utah Arizona border. Those lakes have one source, the Colorado river. In addition to the 40 million people, there are 7 Indian tribes, 7 National Wildlife Refuges, 11 National Parks and 5.5 million irrigated acres with legal rights to the water from these two lakes. Nearly 40 percent of Arizona’s water supply comes from Lake Mead. 15% of California’s surface water comes from the Colorado river.