US May Impose Mandatory Limits on Colorado River Water Use

The US Interior Department is preparing to impose mandatory cuts to the amount of water seven Western states draw from the Colorado River to avoid a “doomsday scenario” in which 25M people in Southwestern cities are unable to get water from the system.

Plunging water levels at the reservoirs at Lake Powell and Lake Mead—the nation’s largest—are approaching the point where the Hoover and Glen Canyon dams will have to be shut down, turning the nation’s largest dams into obstacles to the delivery of water in the Southwest.

The federal government has asked the seven Western states that rely on the Colorado River as a primary source of water to voluntarily cut usage by 2 to 4 million acre-feet—up to a third of the river’s annual average flow—but the affected states have missed an August deadline to reach a consensus on where the cuts will be made.

If they fail, the Interior Department has indicated it will make unilateral cuts next year, according to a report in the Washington Post.

The choice is coming down to people versus agriculture: the historic drought in the Western US—which may be the beginning of a new normal predicted by climate scientists—is pitting vegetable farmers in California against one of the fastest-growing urban areas in Phoenix.

“Without immediate and decisive actions, elevations at Lake Powell and Mead could force the system to stop functioning,” Tommy Beaudreau, the Interior Department’s deputy secretary, told a conference of Colorado River officials meeting in Las Vegas last week, the Post reported.

Ted Cook, general manager of the Central Arizona Project—the agency that deliver’s the river’s water to Arizona—warned that the reservoirs at Lake Powell and Lake Mead are in danger of turning into “dead pools” within the next two years, effectively shutting down the turbines at the Hoover and Glen Canyon dams.

Lake Powell may hit dead pool status as early as next July.

“We may not be able to get water past either of the two dams in the major reservoirs for certain parts of the year. This is on our doorstep,” Cook said, in the newspaper report.

What are known as the Upper Colorado River Basin states—Colorado, New Mexico, Utah and Wyoming—are less dependent on allocations from reservoirs. The lower basin states—Southern and Central California, Arizona and Nevada, which use far more water than their northern counterparts, are in the cross-hairs of the impending water crisis.

What has been called a 1,500-year drought has already led Southern California water providers to declare a regional drought emergency. A record number of wells have run dry in California, forcing acres of farmland to lie fallow.

Lake Mead and Lake Powell held nearly 50M acre-feet of water in 1999, a level that has fallen to 13M acre-feet (each acre-foot equals 326K gallons, enough to cover an acre of land with a foot of water), about 26% of capacity.

Exacerbating the problem is the fact that water usage has exceeded the annual flow of the river in the past two decades, with an estimated 15M acre-feet consumed annually from a river that has an annual flow of about 13.4M acre-feet.