Colorado River water supply to California farms could be threatened by hotter, drier future years
If the Colorado River were to become unusable, Southern California would lose one-third of its water supply. And vast swaths of farmland in the state’s southeastern desert would go unplanted.
SACRAMENTO, Calif. — When Don Cox was looking for a reliable place to build a family farm in the 1950s, he settled on California’s Imperial Valley.
The desert region had high priority water rights, meaning its access to water was hard for anyone to take away.
“He had it on his mind that water rights were very, very important,” said his grandson Thomas Cox, who now farms in the Valley.
He was right. Today, the Imperial Valley, which provides many of the nation’s winter vegetables and cattle feed, has one of the strongest grips on water from the Colorado River, a critical but overtapped supply for farms and cities across the West. In times of shortage, Arizona and Nevada must cut back first on water.
But even California, the nation’s most populous state, with 39 million people, might be forced to give something up in the coming years as hotter and drier weather causes the river’s main reservoirs to fall to dangerously low levels. If the river were to become unusable, Southern California would lose one-third of its water supply. And vast swaths of farmland in the state’s southeastern desert would go unplanted.
“Without it, the Imperial Valley shuts down,” said JB Hamby, a board member for the Imperial Irrigation District, which holds rights to the largest share of Colorado River water.
A century ago, California and six other states — Arizona, Colorado, Nevada, New Mexico, Utah and Wyoming — created a compact that split the water from the Colorado River into two basins and set rules for how much water each state would get. A series of deals, laws and court cases that followed led California to get the most water — and made it the last to lose in times of shortage.
Fear and frustration over California’s use of the river has driven the compact since its early days. In western water law, the first person who taps the source gets the highest right, and California cities and farmers have relied on the river for more than a century.
Other western states worried that California would lay claim to all the river’s water before their own populations grew. The compact and the deals that followed tried to find a balance to protect California’s supply while ensuring that other states got some, too. California, meanwhile, benefited when the federal government began building the Hoover Dam to help control the river’s flow.
Now, the states are gearing up for a 2026 deadline to renegotiate some of the terms to better deal with drought and protect two major reservoirs: Lake Powell and Lake Mead.
Before that, the U.S. Bureau of Reclamation has demanded the states find a way to cut their use by roughly 15% to 30% to stave off a crisis. The states failed to meet a mid-August deadline to reach a deal, but negotiations are continuing.
All eyes are on California and its major water rights-holders — namely the Imperial Irrigation District and Metropolitan Water District of Southern California — to see whether they will give up some of their share. Both districts say they’re willing to use less water or pay others to do so — especially if cooperating means they can avoid challenges to their senior rights.
But they’re playing coy about what exactly they’re willing to give.
The river is the only water supply for the Imperial Irrigation District, whose farmers grow broccoli, onions, carrots and other winter vegetables as well as alfalfa and other feedstock. The limited water underneath the ground in the region, near California’s border with Arizona and Mexico, isn’t usable, and it doesnt have access to state water supplies.
The irrigation district historically has been entitled to more water than either Arizona or Nevada, though it’s given up some of that over the years in exchange for payments from cities like San Diego and Los Angeles. In 2019, its board rejected a drought contingency plan signed by other water users in Arizona, Nevada and California.
This time, officials say the district would be open to leaving fields unplanted to save water on a temporary, emergency basis. But they won’t say how much.
State officials are looking to the $4 billion approved by Congress for the Colorado River as a possible source of money to pay the district and, in turn, farmers, to use less water.
Farmers are trying to organize to avoid having cuts foisted on them, Cox said. Many have installed drip irrigation lines that use less water, but they would be willing to adopt more conservation tactics if aid to do so.
Cox said he’s deciding whether to plant on all of his vegetable fields this fall because he’s getting less water than normal under a new system adopted by the board.
“With water uncertainty, there’s going to be more uncertainty on food supply,” he said.
It’s not just farmers who rely on the Imperial Irrigation District’s water. Runoff from the farms feeds the Salton Sea, a massive inland lake created in the early 1900s when the Colorado River flooded. It’s now rapidly drying up, exposing surrounding communities to toxic dust and killing the habitat that birds and fish rely on. The state and the federal government are looking for other ways to support the sea in the absence of river water, and its being eyed as a possible site for lithium extraction.
“We’re talking about a body of water surrounded by communities who have been marginalized for so [long], that don’t have the infrastructure or capacity to protect themselves from climate change, from less availability of water, from more dust,” said Silvia Paz, executive director for Alianza Coachella Valley, an organization fighting to improve the economy and health outcomes in the region.
Behind the irrigation district, the Metropolitan Water District is the state’s second-largest user of the river’s water. The Colorado makes up about one-third of the water supply the district uses to provide water for drinking, bathing, landscaping and recreation to roughly half of the state’s population.
Los Angeles County, the nation’s largest, is one of many areas in Southern California that relies on the river’s water. It’s allowed to store some of the water it doesn’t use in Lake Mead, which California officials say has helped stave off a river crisis in recent years. But this year, short on other supplies, the district might try to pull some of that water out if needed, which likely would cause friction with other states.
“What they really want is reliability and predictability,” said Michael Cohen, a Colorado River expert with the Pacific Institute. “What they don’t want is Arizona screaming that Phoenix and Tucson are dried up, and California doesn’t take a drop of reductions.”