At the Margins

Across the Colorado River Basin precipitation has been well above average, and while it has not been enough to make up for a weak winter snowpack, it has been enough to improve things significantly at the margins, at a time when “at the margins” is where the basin’s managers have been eking out a nerve-wracking existence. In particular, a 2016 Lower Basin shortage declaration, which would have mandated reduced water deliveries to Central Arizona, seems a lot less likely.

Lake Powell ended May with a surface elevation above 3,596 feet above sea level, four feet above the projection when the month began. That’s an extra 400,000 acre feet of water. Lake Mead, less dependent on weather and more dependent on releases from upstream, is nevertheless a foot above its projections, an elevation above 1,076. The result is a forecast of more than 5 million acre feet of April-July runoff into Lake Powell, up from a forecast of just 3 million acre feet (maf) just a month ago. That is still well below the long term mean of just above 7 maf for April through July, but given the slim margins that were facing water managers the bonus water provides a crucial boost.

Lake Mead sunk to a record low on June 23rd, falling below the point that would trigger a water-supply shortage if the reservoir doesn't recover soon. Water managers expect the lake's level to rebound enough to ward off a 2016 shortage thanks to a wetter-than-expected spring. But in the long run, as a U.S. Bureau of Reclamation spokeswoman said, "We still need a lot more water." The reservoir stores water for parts of Arizona, Southern California, southern Nevada and northern Mexico—all of which have endured a 15-year drought that continues. The U.S. Bureau of Reclamation will announce a 2016 shortage in August if it projects Lake Mead won't rise above 1,075 feet by January. But June’s record low, registering 1,074.99 feet, signals that Colorado River water users consume more than the river provides, said water-policy manager Drew Beckwith of the Western Resource Advocates, a nonprofit environmental law and policy organization. "This is the check-engine light," Beckwith said. "It really does (make critical) the fact that we have to start changing."