The U.S. government warned on Friday that it may impose water supply cuts on California, Arizona and Nevada to protect the Colorado River and its two main reservoirs from overuse, drought and climate change.
The U.S. Bureau of Reclamation unveiled three possible action plans: one to impose cutbacks, another to allow western states to work out a reduction plan on their own, or a third and least likely option of taking no action.
Besides protecting drinking water supplies, the proposed federal action might also preserve hydroelectric production at the country’s two largest reservoirs.
The bureau, part of the Department of Interior, had previously set a mid-August deadline for seven western states to negotiate their own reductions or possibly face mandatory cutbacks.
When the deadline passed, federal officials gave the states more time to reach a deal affecting the water supply of 40 million people. While federal officials still prefer a negotiated settlement, that time appears to be running out, as the bureau said it would stop hearing public comments on the proposals on Dec. 20.
“We are committed to taking prompt and decisive action necessary to protect the Colorado River System and all those who depend on it,” Interior Secretary Deb Haaland said in a press statement.
The seven states operate under a 100-year-old compact distributing Colorado River water, but that agreement has come under increasing strain from the worst drought in 1,200 years, which has been exacerbated by climate change.
A century ago, the compact assumed the river could provide 20 million acre-feet of water each year. The river’s actual flow the past two decades has averaged 12.5 million acre-feet, leaving state water managers with more rights on paper than water that exists in the river.
Friday’s notice said that among the cutback options being considered was decreasing the amount of water set aside for consumption in the 2023/24 water year by the three states of the so-called Lower Basin: California, Arizona and Nevada.
The Upper Basin states of Colorado, New Mexico, Utah and Wyoming would be spared for now, but are still being asked to participate in negotiations to cut usage by an unprecedented 15% to 30%.
Other possible measures include modifying operations at Hoover Dam, which forms the country’s largest reservoir of Lake Mead, and reducing the amount of water released from Glen Canyon Dam, which forms Lake Powell, the second-largest reservoir.
Lake Mead was at 29% of capacity on Friday and Lake Powell 24%. If they fall much lower, they will be unable to generate hydroelectric power for millions in the west.