As six states turn up the heat on California to cut back on water consumption from the Colorado River Basin, the state has proposed its own plan, citing a 1922 contract that grants California senior water rights.

Under the six-state proposal, Southern California water agencies would be required to reduce their water allocation by as much as 32 percent if Lake Mead—the largest water reservoir in the U.S. formed by the Hoover Dam on the Colorado River and which straddles Nevada and Arizona—levels keep dropping.

The proposal comes in the wake of criticism over trillions of gallons of water from heavy rainfall that flowed out to sea in January, despite nearly a decade of promises from Democrats, including California Gov. Gavin Newsom and his predecessor former Gov. Jerry Brown, to build more water reservoirs in the state.

Like California, the other states—Arizona, Colorado, Nevada, New Mexico, Utah, and Wyoming—depend on water from the Colorado River, which supports 40 million people, nearly 6 million acres of agriculture, and native tribes across seven states and portions of Mexico.

According to United States Geological Survey research released in 2020, the river’s flow is down by about 20 percent compared to the 1900s, and has been decreasing ever since by 5 percent per degree Fahrenheit as a result of “atmospheric warming.”

The six states issued the proposal for cutbacks to both the federal Interior Department and the U.S. Bureau of Reclamation on Jan. 31. But, California’s senators—Sen. Dianne Feinstein and Sen. Alex Padilla—rejected it, saying it would hurt the state’s cities and farmers and urged consensus among all seven states.

“We know that drought caused by climate change will require changes to Colorado River water use and that no state will be spared from water reductions,” the senators said in a joint statement Jan. 31, adding that California came up with its own plan last fall to voluntarily reduce water use.

“But six other Western states dictating how much water California must give up simply isn’t a genuine consensus solution—especially coming from states that haven’t offered any new cuts to their own water usage,” they said.

The senators additionally argued the states’ proposal “further fails to recognize California’s senior legal water rights.”

Last fall, California offered to conserve 400,000 acre-feet of water each year through 2026 to protect water storage levels in Lake Mead.

Its water agencies have proposed what they call a “modeling framework” for the U.S. Bureau of Reclamation to evaluate. The plan includes reducing water use while protecting infrastructure and prioritizing public health and safety, while upholding what’s known as the “Law of the River,” which are laws, compacts, decrees, and previous agreements that govern how water from the Colorado River is used.

The proposal asks Arizona, in particular, to cut back on water usage, just as California says it is attempting.

“[S]o too may the State of Arizona be required to make similar arrangements to live within its available Colorado River water supplies,” the document states.

The proposed framework seeks to keep Lake Mead water levels at 1,000 feet and Lake Powell in Utah and Arizona, the second largest U.S. water reservoir, at 3,500 feet by modifying reservoir operations and “phased water use reduction.”

JB Hamby, chairman of the Colorado River Board of California and California’s Colorado River Commissioner, supported the framework in a letter to the Bureau of Reclamation

saying it was both realistic and implementable by building on new voluntary agreements and past collaboration amongst the affected states.

Additionally, California Natural Resources Secretary Wade Crowfoot said in a statement Feb. 1 that California’s proposal is “a timely, practical and achievable in a way that works within existing law.”

According to Lisa Lien-Mager, a spokesperson for the agency, said officials have been actively managing the State Water Project—the state’s delivery system consisting of canals, pipelines, reservoirs, and hydroelectric power facilities to deliver clean water to 27 million residents—to take advantage of heavy rainfall that drenched the state in late December and early January.

“We have moved significant amounts of water into storage,” and expect several projects will capture excess flows to refill groundwater basins, she said in an email.

Meanwhile, discussions among the seven states are continuing with several meetings planned between now and April, she said.

According to Lien-Mager, the U.S. Bureau of Reclamation expects to issue this year’s plan—called an environmental impact statement—for the states in March as a draft laying out alternatives in advance of the document being finalized by August, as is customary.

In addition to the State Water Project, the Colorado River is an important water source for urban Southern California, and the sole source of supply for the Imperial Valley in Riverside and Imperial counties, she said.

Water users in California who rely on the Colorado River have since 2003 reduced usage and conserved more than 1.5 million acre-feet of water in Lake Mead over the past 15 years, according to Lien-Mager.

“California has a track record of action and will step up again because extraordinary measures are needed,” she said.