By Andrew Hay
July 31 (Reuters) - The U.S. government proposed deep cuts to water supply for Arizona, California and Nevada during dry years in a new plan it released on Friday to operate the drought-stricken Colorado River.
Lawsuits from states could challenge the federal intervention and could mean years more uncertainty for a river that 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.
Those seven states
— Colorado, New Mexico, Utah, Wyoming, Arizona, California and Nevada, known as the basin states — were unable to agree on how to share the water after over three years of talks to replace a plan that expires this year.
The U.S. Bureau of Reclamation intervened with a 10-year proposal through 2036 designed to provide flexibility to operate the river's two largest energy-producing reservoirs — Lake Powell and Lake Mead — based on severe drought and chronic overuse, according to a final environmental impact statement released by the agency.
"This framework provides the flexibility to respond to changing hydrologic conditions while preserving the opportunity for the Basin States to continue working toward durable, consensus-based solutions," Secretary of the Interior Doug Burgum said in a statement.
The plan sets limits on how the river would be operated, and envisages water shortages of up to 3 million acre-feet per year in the three Lower Basin states.
CUTS NEARLY DOUBLE STATES' PROPOSAL
That is nearly twice the reduction in water supplies the Lower Basin states proposed on May 1 of 1.6 million acre-feet per year through 2028.
In a statement, the Arizona Department of Water Resources called the Bureau of Reclamation proposal "unacceptable" and noted it did not require cuts of the four Upper Basin states.
"Such reductions would devastate Arizona’s water users and its economy," the Arizona statement said.
Arizona said it hoped federal operating guidelines expected to be released later would be consistent with the Lower Basin's May 1 proposal.
JB Hamby, California’s lead negotiator in talks, said the river’s operating plans would be developed in two-year increments, allowing for adaptation to changing water flows.
He said the next step was the federal government’s release of an operating plan for 2027 and 2028.
“This is an important milestone, but it is not the finish line,” Hamby said of Friday’s environmental impact statement.
The Bureau of Reclamation said in a statement that drought conditions over the past 25 years, combined with expectations of continued dry conditions, had made developing future operating guidelines “particularly challenging.”
In 1922, when the river's waters seemed inexhaustible, the seven states created a water-sharing compact dictating how much Upper and Lower Basin states receive. However, the U.S. West is caught in its worst drought in at least 1,200 years, according to a 2022 study by the University of California, Los Angeles. Rising regional temperatures, which scientists largely attribute to human-caused climate change, have led to about a 20% decline in Colorado River flow since 2000.
Water levels in the Lake Powell and Lake Mead reservoirs are at risk of dropping so low that their hydroelectric power plants will stop functioning.
The bureau's cuts are expected to affect Arizona the most. Under river rules, the earlier a town or irrigator started using Colorado River water, the higher their priority if supplies run short.
Water scientist Sharon Megdal has called the river’s condition a natural disaster that will require extraordinary actions to sustain livelihoods in an area that supports an estimated $1.4 trillion in GDP and 16 million jobs.
The 1,450-mile-long (2,330-km) river, the fifth-longest in the United States, is experiencing heat-driven aridification and climate change models predict an additional 20% drop in Colorado River flow by 2050 and 35% by 2100.
(Reporting by Andrew Hay in New Mexico; editing by Donna Bryson, Aurora Ellis, Rod Nickel)
