The Drought Goes On: As Lake Mead Sinks, States Agree to More Drastic Water Cuts

Three years ago, state hydrologists in the Colorado River Basin began to do some modeling to see what the future of Lake Mead—the West’s largest reservoir—might look like. If the dry conditions continued, hydrologists believed, elevations in Lake Mead—which is fed by the Colorado River—could drop much faster than previous models predicted. For decades, the West’s big reservoirs were like a security blanket, says Anne Castle, the former assistant secretary for water and science at the Interior Department. But the blanket is wearing thin. Under normal conditions, Lake Mead loses 1.2 million acre-feet of water every year to evaporation and deliveries to the Lower Basin states plus Mexico; that all amounts to a 12-foot drop. Previously, extra deliveries of water from Lake Powell offset that deficit, but after 16 years of drought and increased water use in the Upper Basin, those extra deliveries are no longer a safe bet. “There’s a growing recognition that even these huge reservoirs aren’t sufficient to keep the water supply sustainable anymore,” says Castle. For the three Lower Basin states—California, Arizona and Nevada—that rely heavily on Lake Mead, the situation is particularly urgent. For the last several years, Mead has hovered around 1,075 feet above sea level, the point at which harsh water-rationing measures kicks in. And if conditions in the reservoir continue to worsen, the Interior Department could even take control of water allocation from Lake Mead...more