(CN) — Arizona, Nevada and Mexico will get less Colorado River water next year after the Bureau of Reclamation on Monday released a key monthly report that determines river water allocations for the coming year.
For the first time, the August 24-Month Study showed Lake Mead’s surface below 1,075 feet, triggering a Tier 1 shortage that will deprive low-priority users of some of their water, said Tanya Trujillo, assistant Interior secretary for water and science.
“Like much of the West and across our connected basins, the Colorado River is facing unprecedented and accelerating challenges,” Trujillo said, adding that her department will face the challenges from climate change and with science and cooperation.
The Colorado River provides water and power to about 40 million people in the West.
Arizona will lose 18% of its river allocation in 2022, Nevada will lose 7%, and Mexico, which gets some water via a treaty with the U.S., will lose 5%, said Jaci Gould, the Bureau of Reclamation’s Lower Colorado River Basin regional director.
Most of those losses will hit Arizona farmers, who within the state have the lowest-priority access to the water. About 70% of water from the river are diverted for agricultural purposes across the West.
The picture would be worse without years of planning and cooperation among federal, state and local governments, Gould said.
“If not for that we would have had to declare a shortage years ago,” she said.
The Colorado River Compact and associated laws and agreements, collectively known as the law of the river, predetermine what happens at various stages of shortage.
Under Tier 1, declared today, Arizona loses 512,000 acre-feet of its allocation, Nevada loses 21,000 acre-feet of its 300,000, and Mexico loses 75,000 acre-feet of its 1.5 million. One acre-foot is 326,000 gallons, about what two average Arizona families of four use in a year.
California gives up none of its 4.4 million acre-feet allocation in a Tier 1 scenario.
Those losses were determined in Reclamation’s 2007 interim guidelines for operation of lakes Mead and Powell, the two largest storage reservoirs on the river. Water levels at Lake Mead, first filled in the 1930s, are at an all-time low.
A later drought contingency plan adopted by the states includes a Tier 0 shortage — declared for this year — under which Arizona lost 192,000 acre-feet.
The Reclamation report released today offers a dismal forecast.
Computer models used to compile the monthly 24-Month Study predict Lake Mead could drop below 1,050 feet by November 2022, triggering a Tier 2 shortage, under which Arizona would lose another 80,000 acre-feet and Nevada an additional 4,000. By July 2023, the furthest forecast in the report, the lake could drop to 1,038 feet, at which point California would take its first cut of 200,000 acre-feet.
“Today’s announcement of a Level 1 Shortage Condition at Lake Mead underscores the value of the collaborative agreements we have in place with the seven basin states, Tribes, water users and Mexico in the management of water in the Colorado River Basin,” said Reclamation Deputy Commissioner Camille Touton in a statement. “While these agreements and actions have reduced the risk, we have not eliminated the potential for continued decline of these critically important reservoirs. Reclamation is committed to working with all of our partners in the basin and with Mexico in continuing to implement these agreements and the ongoing work ahead.”
Arizona’s lower priority for Colorado River Water stems from the 1968 Colorado River Basin Project Act, which authorized the Central Arizona Project, a 336-mile canal from the river at Lake Havasu to Tucson. That canal supplies water to the state’s two major population centers, Tucson (900,000) and Phoenix (4.6 million) and gave California the highest priority among Lower Basin states.
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