In the 1960s, the Bureau of Reclamation built a dam that flooded a celebrated canyon on the Utah-Arizona border. Today, it’s known as Lake Powell — the second-largest reservoir in the U.S.

A half billion dollar tourism industry has grown in the desert around the reservoir but a decades-long megadrought is putting its future in question.

With what some call America’s ‘lost national park’ reemerging, an old debate is also resurfacing: should we restore a beloved canyon or refill a popular and critical reservoir?