What was once a mighty river flowing from Colorado through the Grand Canyon all the way down to the Gulf of California in Mexico has been reduced to a trickle that barely reaches the ocean. 

Experts warn the river basin is at a breaking point, jeopardizing water security for major cities such as Los Angeles and Denver, harming endangered fish species, and putting some of the largest food producers in the US at risk. 

Lakes Mead and Powell, the river's largest reservoirs, are critically low, a product of prolonged drought and rising temperatures. If water levels fall further, hydropower generation at the Hoover and Glen Canyon dams could be curtailed, threatening energy supply and recreation.

"The ultimate cause of the problem in the Colorado River is a warming climate," Jack Schmidt, director of the Center for Colorado River Studies at Utah State University, told DW.

"But the immediate or proximate cause of the entire crisis is our inability to quickly reduce our expenses to match our dwindling income," added Schmidt. In other words: overuse. 

A conflict over worsening water scarcity 

Some 40 million people rely on the river for water across seven states in the US, but the country also has an obligation to deliver supplies to Mexico. About half of the river water is used for millions of acres of nearby farmland and about 18% goes to homes, cities and industry. 

A recent report,which Schmidt co-authored, warned the Colorado River Basin could fall short by the equivalent of 1.8 million Olympic swimming pools next year if consumption continue at current rates. 

That's left California, Arizona, and Nevada in the river's Lower Basin at odds with Colorado, Utah, Wyoming, and New Mexico in the Upper Basin. The states are now locked in high-stakes negotiations over how to share the river's dwindling supply after 2026, when current water-sharing rules expire. 

"We're dealing with the basic issues of scarcity. There's not a lot of a resource that everybody wants and everybody needs," said Kyle Roerink, Executive Director of the Great Basin Water Network. 

Who has the most rights to the river? 

Water rights on the Colorado Riverare a complex web of claims, including the river basin states, Native American communities, and Mexico. There are "varying interpretations" of who has greater rights to water, particularly in times of scarcity, and they've been arguing for years, explained Roerink.

Older "first in time, first in right" water allocations are considered more "senior" and take precedence during shortages. This creates tension between the Upper Basin — Colorado, Utah, Wyoming, and New Mexico — and the Lower Basin — California, Arizona, and Nevada. California holds the most senior rights in the Lower Basin. 

Part of the conflict boils down to overly optimistic calculations of how much water is available. The 1922 Colorado River Compact,which regulates water distribution among the seven states in the southwestern US, overestimated the river's supply, allocating more water on paper than is actually there. 

"States are really scared about what may happen and are essentially trying to say that they have the strongest rights to the water. They are setting up a stage for major conflicts down the road," Roerink said.

The Upper Basin states have long been using less than what was allocated to them, while the Lower Basin pumps its full share. The Upper Basin states want to develop water that was promised to them and demand the downstream states cut back. 

"But the Lower Basin states say: 'We've developed an entire infrastructure, one of the largest economies on Earth in Southern California. We can only reduce so much," said Schmidt. 

The problem with thirsty alfalfa and other animal feed 

The majority of the Colorado's water goes to agriculture. Cattle-feed crops, such as alfalfa and other grass hays, make up close to half of all direct water consumption. 

The Upper Basin wants the Lower Basin to cut agricultural consumption, said Schmidt. However "all of that use of agricultural water are senior water rights, and we can't tell those people not to use the water."

Over the years, efforts to reduce water usage have included paying farmers not to plant certain water-intensive crops. 

But water laws don't allow farmers to be forced to grow less water-intensive crops, such as bean sprouts or barley, instead of alfalfa, Roerink said. There's also no economic incentive to move away from  growing cattle feed, since Americans show no sign of cutting back on beef or dairy.

Negotiating under pressure: What happens next? 

The Colorado Basin states have until November 11 to come to an agreement on cutting real water use before current guidelines expire. If they're unable to reach a deal, the federal government will likely step in and put forward new rules. 

In the meantime, levels are so low in the Mead reservoir, federal authorities recently announced that a Tier 1 water shortage would continue in 2026.That triggers water cuts in Arizona, Nevada and Mexico and spares California due to its senior rights.

And experts such as Roerink and Schmidt say the situation is so urgent that states shouldn't wait until any new guidelines agreed would come into effect in 2026.  

"We have lost our focus on the immediate crisis right before us," Schmidt said. 

What can states do now to conserve water?

The Great Basin Water Network has put forward nine recommendationsfor the river system. These include putting a stop to new dam and diversion projects, pushing all states to cut water use, and encouraging wastewater recycling. 

"The number one thing that we need to ensure is that we are not allowing new uses of water," said Roerink, citing new water-hungry infrastructure such as cryptocurrency farms, data centers for Artificial Intelligence and real estate projects.

But agriculture has the greatest potential to ease the Colorado River crisis, according to the network. Crop rotations, advanced irrigation techniques, building canals, and investing in dry farming techniques could help save water that farmers could sell or lease to cities in times of drought.

"It is inevitable that we must make agricultural use of water much more efficient than it is, so that we can still maintain viable agricultural communities," Schmidt said. "Reducing growing alfalfa and grass in the heat of summer when it's 120 degrees Fahrenheit [49 degress Celsius]. We need to be targeted in where we grow crops."

Edited by: Jennifer Collins