The Glen Canyon Dam is dangerously close to deadpool because it was built with a significant design flaw: There is no drain at the bottom. If the reservoir continues to decline, billions of gallons of water would be trapped in the dead-pool reservoir with no easy way to release the water into the Grand Canyon, writes Zak Podmore, who has a new book coming out on the subject. What once was heresy, he says, must now be considered: Drain Lake Powell.