Two weeks ago, experts predicted that Lake Powell — the second-largest man-made reservoir in the nation — will soon drop below critical water levels. With over three million people in danger of losing hydropower, it’s yet another bleak reminder that the Colorado River is drying up.

The Colorado River, which flows into Lake Powell on the Arizona and Utah border, originates at 10,184 feet above sea level on La Poudre Pass in the southern Rocky Mountains. In total, 40 million people gain water access from the river, and countless farms are irrigated along the way.