WEDGED between Arizona and Utah, less than 20 miles upriver from the Grand Canyon, a soaring concrete wall nearly the height of two football fields blocks the flow of the Colorado River. There, at Glen Canyon Dam, the river is turned back on itself, drowning more than 200 miles of plasma-red gorges and replacing the Colorado’s free-spirited rapids with an immense lake of flat, still water called Lake Powell, the nation’s second-largest reserve.

When Glen Canyon Dam was built in the middle of the last century, giant dam projects promised to elevate the American West above its greatest handicap — a perennial shortage of water. These monolithic wonders of engineering would bring wild rivers to heel, produce cheap, clean power and stockpile water necessary to grow a thriving economy in the desert. And because they were often remotely located, they were rarely questioned.

But today, there are signs that the promise of this great dam and others has run its course… Read more from the New York Times