Rolf Schmidt-Petersen knows what can happen when a water shortage hits: Reservoirs shrink and tempers flare.

“We had people literally throwing rocks, tomatoes when Elephant Butte went down,” recalled Schmidt-Petersen, director of the New Mexico Interstate Stream Commission. He was talking about a 2003 deal to release water from a reservoir in southern New Mexico and drop the lake by about 33 feet to assist farmers in the state and neighboring Texas.