Lake Powell, a 190-mile long reservoir in Utah that holds back the Colorado River, and which can hold 24 million acres of water, has dropped 140 feet since 2000 and 50 feet in the last year. But as the lake's surface recedes, leaving a bathtub-like ring marking its evaporation, Glen Canyon, a natural wonder which was partially flooded by the dam, has reemerged. As Elizabeth Kolbert writes, in that canyon, we are seeing the Colorado River restore itself in real time. Well talk to Kolbert about what it's like to celebrate "the effects of what, by most standards counts as a disaster" and the confounding feelings of finding silver linings in climate change.