By Andrew Hay and Nichola Groom
Aug 21 (Reuters) - The U.S. government on Friday finalized a two-year plan to slash water supplies to California, Nevada and Arizona to manage the drought-stricken Colorado River, while leaving open the possibility of far deeper cuts later in the decade.
The three so-called lower basin states will take around a 21% reduction in water from the river in 2027 and 2028, but cuts could nearly double in later years, according to the plan signed by Interior Secretary Doug Burgum.
Arizona and Nevada have said any plan to double the cuts after 2028 would devastate their economies. Arizona has threatened to sue the federal government if it imposed these potential cuts as part of the new 10-year plan.
Colorado, Utah, New Mexico and Wyoming, the upper basin states, face no mandatory cuts under the plan. The Colorado River provides water to one in 10 Americans, irrigates land producing 15% of U.S. food output and generates power for 6 million people in seven states.
The river's governing agreements allocated roughly equal amounts of water to the two basins in 1922, but California, Arizona and Nevada have historically consumed more water, a central point of contention.
Arizona Governor Katie Hobbs, a Democrat, applauded the federal government for adopting the Lower Basin's proposal for water cuts in 2027 and 2028. But she said the government's 10-year plan fell short of providing water Lower Basin states were entitled to. She called the Upper Basin’s refusal to negotiate reductions to their water usage "reckless."
"Arizona stands prepared to protect our water by any legal means necessary and won't back down in defense of our rights," Hobbs said in a statement.
In three years of failed negotiations between the seven states, Upper Basin states refused to take cuts, arguing they face declining water supplies due to the severe drought impacting the U.S. West.
The river’s Lake Powell and Lake Mead, the nation’s two largest reservoirs, hit record lows this month. The water level of Lake Powell sat at 3,519.2 feet above sea level on Thursday — less than 30 feet above the minimum level needed to operate the Glen Canyon Dam hydroelectric power plant in Arizona.
In line with a May 1 proposal made by the Lower Basin states, their water allocation will be reduced by a combined 1.6 million acre-feet per year in both 2027 and 2028.
The reductions consist of 1.25 MAF per year in mandatory cuts and an agreement by the three states to conserve 700,000 MAF over the two years to reach combined water savings in the two-year period of 3.2 MAF.
However, annual mandatory cuts to the three states could almost double to 3.0 MAF per year if needed to maintain critical reservoir levels following the first two-year operating period.
Any lawsuits over those potential cuts could mean more years of uncertainty.
California Governor Gavin Newsom said all seven states that depended on the Colorado River needed to conserve water.
"This operations plan provides only short-term stability," Newsom said in a statement. "Any long-term solution must share responsibility fairly across all seven states in recognition of the new reality of the Colorado River."
Hydrologist Sarah Porter still saw a strong chance Arizona would sue the federal government over its 2029 through 2036 plan. She said the state objected to the Bureau of Reclamation's assessment of its authority to cut water deliveries from Lake Mead to Lower Basin states and not impose mandatory cuts on upper basin states.
"The Bureau has made clear that if reservoir elevations decline to certain points, the Bureau may impose deeper cuts or limit releases from Lake Powell or take other actions in the future far beyond what the Lower Basin has agreed to," said Porter, director of the Kyl Center for Water Policy at Arizona State University.
(Reporting by Nichola Groom in Los Angeles and Andrew Hay in New Mexico; Additional reporting by Jasper Ward in New York; Editing by David Gregorio)
