Nevada’s Lake Mead, the biggest reservoir in the West, is on track to fall below a critical threshold in 2020, according to a new forecast by the Bureau of Reclamation. In a prediction released Wednesday, the Bureau of Reclamation, a multistate agency that manages water and power in the West, said there is a 52% probability that water levels will fall below a threshold of 1,075 feet elevation by 2020. If Lake Mead’s water levels fall below that threshold, it could trigger the first ever federal shortage declaration on the Colorado River—which experts say could undermine the Southwest’s economy. “The very big concern is the perception that water supplies are uncertain,” said Todd Reeve, chief executive officer of Business for Water Stewardship, a nonprofit group in Portland, Ore., that works with businesses on water use nationally. “So if a water shortage is declared, that would be a huge shot […]