Despite signs of interstate cooperation, the decline of Lake Mead isn’t near being solved
On the surface, things have seemed to be looking up in recent weeks for the future of Lake Mead.
The Western storms of the last month have fostered the impression of a respite, at least temporarily, from the region’s long drought. Earlier this month, Arizona legislators passed a sheaf of crucial measures signaling their willingness to cooperate in an interstate drought contingency plan, staving off federal intervention.
Yet these are stopgaps. The giant reservoir on the Colorado River behind Hoover Dam, which provides water chiefly to residents in California and farmers there and in Arizona, is suffering from a long-term and possibly irreversible decline in capacity.
The ultimate danger is that the lake reaches the “dead pool” stage. At the end of January, the lake was at 1,086 feet of surface elevation above sea level. When it reaches 1,050 feet, the lake can no longer generate hydroelectricity. At 895 feet, it can’t provide water.
Lake Mead’s enemies are both natural and man-made. Climate change has placed the Colorado River basin in a long-term drought. Meanwhile, human demands for water from the Colorado have far outstripped what it can provide.
“We’re in the 19th year of a drought,” observes Robert Glennon, an expert on water policy at the University of Arizona, “and it’s pretty obvious that climate change is having a devastating impact.” That places a premium on interstate cooperation to address the drought’s consequences — chiefly how to apportion what is certain to be a diminishing supply of Colorado water.
The fate of Lake Mead really was sealed in 1922, well in advance of its existence, with the drafting of a seven-state compact governing distribution of the waters of the Colorado River. (Besides California and Arizona, the states are Nevada, Colorado, Utah, Wyoming and New Mexico.) To secure the agreement clearing the way for Congress to advance money for the dam, then-Commerce Secretary Herbert Hoover deliberately overestimated the river’s capacity so that no state would fear getting shortchanged.
Construction of the dam and the filling of Lake Mead helped fuel epic population growth in the Colorado River basin, especially in California. Eventually it became clear that growth would outstrip the river’s capacity to deliver all the water that was promised.
On the lower basin (California, Arizona and Nevada), “we’re using 1.2 million more acre-feet than the river hydrology provides,” says Jeffrey Kightlinger, general manager of the Metropolitan Water District of Southern California, one of the largest users of Lake Mead water. “Effectively, we’ve been able to get away with it because the upper basin hasn’t developed as rapidly. But we’re living on borrowed time.”
One acre-foot equals about 326,000 gallons, enough to serve one or two average California households.
The MWD, the principal source of water for Southern California residents, gets about 15% of its water from the Colorado, 30% from Northern California via the State Water Project, and the rest from local sources, including groundwater and transfers from agricultural districts.