The Colorado River has long been used to irrigate crops, provide drinking water and support critical habitat in the American West. For more than a century, its water has been divvied up and diverted, conserved and purged, based on a 1922 agreement that guaranteed allotments of the wet stuff for the seven states that depend on it.

But those states are likely to miss a critical federal deadline Saturday to revise their usage in the face of dwindling river flows and the growing populations that depend on them.

How many Americans rely on the Colorado River?

Over 40 million Americans depend on the river, according to the Nature Conservancy. Stretching for 1,450 miles from the Rocky Mountains in Colorado to the Gulf of California off Mexico, it’s a major source of water for Arizona, California, Colorado, Nevada, New Mexico, Utah and Wyoming, as well as 30 tribal nations.

About half of the river’s water is used to irrigate crops, which contributes to about 15% of the country’s overall agriculture production and 90% of the nation’s winter vegetables, according to the bipartisan nonprofit Environmental and Energy Study Institute. About 18% is used in urban areas and 19% supports natural vegetation, the EESI said.

How is the Colorado River water shared?

The water is shared based on something known as the law of the river as determined by the 1922 Colorado River Compact. Negotiated by then-U.S. Secretary of Commerce Herbert Hoover, its purpose was to equitably divide the river by establishing different levels of importance for the water’s beneficial uses, according to the U.S. Bureau of Reclamation.

The compact was intended “to remove causes of present and future controversies and to secure the expeditious agricultural and industrial development of the Colorado River Basin, the storage of its water and the protection of life and property from floods,” the bureau said.

What is happening February 14?

The U.S. Bureau of Reclamation has set February 14 as the deadline for seven states to agree on how to manage the river.

In 2007, the seven states that are part of the Colorado River compact created short-term guidelines for conservation and water-sharing during droughts that will expire at the end of 2026, forcing them to develop new rules.

“The clock is ticking to come up with a new management framework, but we are dealing with 21^st century aridity problems in a system that was developed for a 20^th century wetter world,” Great Basin Water Network Executive Director Kyle Roerink told Spectrum News. “What we see here are states fighting one another about who should get what, when and how and who should make reductions, when and how.”

What are the states getting now?

According to the 1922 pact, the river is divided into two basins: the upper basin states of Colorado, New Mexico, Utah and Wyoming and the lower basin states of Arizona, California and Nevada.

The upper basin and lower basin are each allocated 7.5 million acre-feet per year, with the upper basin required to deliver 75 million-acre feet annually to the lower basin.

What are the seven states wrangling over?

The states are grappling with lower Colorado River levels because of a hotter, drier climate.

When the 1922 pact became law, it was based on about 18 million acre-feet of water being available, but the average today is about 12 million acre-feet, Roerink said, likening the loss to the equivalent of 6 million Olympic-size swimming pools.

“The best scientists are telling us that we haven’t yet hit the floor of what we’re going to bottom out at in the 21^st century,” he said, adding that the river could lose another 2 million acre-feet by the middle of the century.

The negotiations are taking place as the National Centers for Environmental Information reported that last month was the fifth warmest January since 1850 with average temperatures more than 2 degrees above the 20^th century average. The NCEI said Arizona, California and Utah have had exceptionally warm starts to the year.

While the lower basin states have cut their use for years and say they are willing to reduce it by another 1.5 million acre-feet, the upper basin states will not accept mandatory cuts because they have never used their full allocation and are more vulnerable because they lack reservoirs to store water like lower basin states, according to John Berggren, Western Resource Advocates regional policy manager.

What happens if the states can’t come to consensus by February 14?

“The states not having an agreement means that they are walking into their legal corners and preparing their lawyers for litigation,” Berggren told Spectrum News. “The basin states have always said litigation is failure, and they want to avoid it at all costs, but we’re really looking at that as a possible scenario now.”

Arizona and Utah have each bolstered their legal coffers for an impending and protracted legal battle, according to news reports. Berggren said the case could spend a decade being litigated and end up at the Supreme Court.

“Who knows what the Supreme Court’s going to decide? And while that whole thing is in process, what are we doing?” he said, adding that litigation provides no certainty and a lot of risk for the states involved.

Both the lower and upper basin states will ultimately have to use less.

“Everyone who’s getting cut has to know that everyone else is doing their part,” he said. “It’s not about what you were given on paper 100 years ago. It’s what is actually flowing in the river.”

While the Colorado River compact asserts that the states are in control of the water that flows through them, the federal government is responsible for the management and operation of the river’s major dams as well as the reservoirs that serve as a water piggy bank and are currently below healthy levels.

If the states fail to reach an agreement, the federal government could step in with its own proposals.

The Bureau of Reclamation has outlined six scenarios. One plan would give the bureau the authority to do whatever it deems necessary while others incentivize states to reduce their water use or divvy up the river based on available supply or leave the current allocations in place.

What are the implications for people living in states that depend on Colorado River water?

“This is something that will definitely impact water bills for ratepayers in metropolitan areas,” Roerink said, adding that lower river levels could reduce hydroelectric power generation.

“This is something that is going to impact prices at the grocery store,” he said, referencing less agriculture.

In Arizona, which has lower-priority Colorado River rights than California, cities like Phoenix may not be able to continue to grow, he said, while endangered fish, avian and reptile species will be at risk and river rafters may no longer be able to travel through the Grand Canyon.

Less Colorado River water, Roerink said, “is going to mean big problems — things we’ve never seen before.”