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The Colorado River Is Overcommitted. Here's Why — And What We Can Do About It

In the very early years of the 20th century, Western leaders had big dreams for growth, dreams tied to bringing water from the Colorado River across mountains and deserts.

In dividing up the river, they assigned more water to users than the system actually produces. The consequences of the so-called “structural deficit” are being felt today, as states sweat through difficult river diplomacy to prop up water levels in reservoirs. 

The Colorado River basin states have acknowledged this “structural deficit” for a while, but why did it happen in the first place? 

Divvying Up The River

In their new book "Science Be Damned," authors John Fleck and Eric Kuhn lay out the history of how the river was divided.

Using Colorado River water for large-scale farming, housing, and industry took “significant investment,” Fleck said in an interview. “It created a situation where the actions of one party could really affect other people using the river.”

In the early 1920s, leaders of the seven basin states (Arizona, California, Nevada, Colorado, Wyoming, New Mexico and Utah) and the federal government met to come up with a deal to share the river. The result of their work became the Colorado River Compact.

Measuring The River

Dividing up the water first meant measuring the water.

“They had about 20 years of records from actually putting stream gauges in the river and measuring its flow,” Fleck said. “And the conventional story is: ‘Well, what bad luck. They did the best with what they had at the time, and allocated more water than the river actually has, because they didn’t realize it was an unusually wet period.”

But Fleck and Kuhn argue it wasn’t just “bad luck.” The subtitle of the book is "How Ignoring Inconvenient Science Drained the Colorado River." The authors describe how the research existed that would’ve led to a better decision.

“There were scientists who looked at earlier evidence showing that there had been, in fact, big droughts in the late 1800s, and that evidence was simply ignored as an act of sort of political convenience,” Fleck said. “It was much easier to solve the problem if everybody thought there was a lot of water.”

More water means the Compact was easier to sell back home, and no one had to give up their dreams. 

Fleck and Kuhn wrote about the efforts of scientist E. C. LaRue of the United States Geological Survey. LaRue estimated Colorado River levels in part using records Mormon settlers kept of the Great Salt Lake, which is outside the Colorado River basin, but nearby.

According to "Science Be Damned,"  LaRue’s research, along with that of another scientist, Herman Stabler, put the average “natural” flow of the river at about 15 million acre-feet a year for the period of the mid-1870s to 1922. That’s remarkably close to the 14.8 million acre-feet a year that modern scientists say the river provides. (An acre-foot is an acre of land covered with a foot of water.)

But LaRue’s estimates weren’t really part of the conversation.

Politicians like Delph Carpenter, the famed lawyer from the state of Colorado, ultimately went with a more generous number: 7.5 million acre-feet for the Upper Basin (Colorado, Wyoming, New Mexico and Utah), and 7.5 million acre-feet for the Lower Basin (Arizona, California, Nevada). The Compact accounts for Arizona’s use of its in-state rivers by allowing the Lower Basin to use an additional one million acre-feet. Mexico’s 1.5 million acre-feet would come in a later treaty.

Ignoring The Science

Did Carpenter and others believe their own fiction?

“It certainly appears, based on all the available records that we’ve been able to find, that Delph Carpenter and the others who really wanted big development on the river weren’t knowingly lying. They were sort of engaging in the problem of confirmation bias,” Fleck said. “They really wanted the flows to be big, so they had a way of dismissing LaRue, saying, ‘well, we really can’t trust that kind of science because we really want gauge records.’”

And mostly, LaRue was just kind of ignored.

Fleck said river managers didn’t really confront the reality of the river’s lower flow until Congress negotiated the Central Arizona Project canal.

“In 1968 when the Central Arizona Project was approved, Arizona knew that there was not sufficient water to keep that canal full year in and year out,” Fleck said. 

He points to testimony from then-Reclamation Commissioner Floyd Dominy, who told a House of Representatives subcommittee that “sooner or later, and mostly sooner, the natural flows of the Colorado River will not be sufficient to meet water demands, either in the lower basin or the upper basin, if these great regions of the Nation are to maintain their established economies and realize their growth potential.”

Fleck said Arizona knew that without augmentation, the water available for CAP canal customers would fluctuate.

“And somehow that was forgotten, and Arizona grew to depend on a full CAP canal every year,” Fleck said.

'Accepting' The Science

The river’s structural deficit is about 1.2 million acre feet each year. That’s an annual overcommitment of almost four Phoenixes covered in a foot of water. As more users actually use their full allocations, the imbalance contributes to drops in Lakes Mead and Powell, the two main reservoirs. Declines led to the temporary shortage guidelines signed in 2007 and updated this year.

Today’s negotiators are preparing to tackle the structural deficit in a new agreement that will replace the guidelines, which expire in 2026. Fleck said these modern folks adhere much closer to science than their predecessors did.

“We are much better now at accepting rather than ignoring inconvenient science,” he said. “You see serious analytical work being done within the federal agencies even in the midst of the Trump administration’s attitude toward climate change.”

The truth about the river may finally be too powerful to ignore. 

Getting The Colorado River Back In Balance

Along with climate change, the deficit is one of the big reasons why Lake Mead has dropped in recent years.

Fixing it could be a big problem for Arizona.

“Unfortunately, Arizona’s facing some of the largest cuts and it really puts Arizona in a political vice,” said Brad Udall, a research scientist at Colorado State University. “You can’t take that much water out of the canal, the entire 1.2 million acre-feet, and do justice to Arizona’s water needs. Yet that’s what the 1968 law says.”

The 1968 Law

The 1968 law is the Colorado River Basin Project Act. It lent federal money to build the Central Arizona Project but created a long-lasting downside for the state: the  water rights for Central Arizona Project customers are junior to California’s water rights when there’s a shortage. Customers of the Central Arizona Project canal currently  receive roughly 1.4 million acre-feet a year.

So the easy answer to the structural deficit could be, tough luck, central Arizona. 

But that is definitely not the view of Tom Bushcatzke, the director of Arizona’s Department of Water Resources. He said the deficit is due to evaporation in Lake Mead and evapotranspiration as water travels from Mead to Mexico. Hence, not just Arizona’s responsibility.

“Arizona, Nevada, California and Mexico, in order to get their allocations delivered to them, are all part and parcel of the creation of the structural deficit,” he said. “We all need to participate in the resolution.”

Fleck called Buschatzke’s stance “very reasonable,” and said evaporation in the Lower Basin of the Colorado River just isn’t accounted for right now.

“To be more realistic about how evaporation is allocated I think is a smart way to do this,” he said.

But that may prove too simple, given the long legal history of the priority system and the need to get multiple states on board in order to make adjustments to the river’s rules. 

Bill Hasencamp manages Colorado River resources for the Metropolitan Water District of Southern California, which serves water to utilities in six counties in the Los Angeles and San Diego areas. He is open to sharing the pain, but said the priority system is important.

“I think there’s some balance where the priority system is recognized and Arizona maybe has to do a little bit more, but that all states and all water users have to be part of the solution,” he said. 

California as a whole has the largest allocation in the lower basin: 4.4 million acre-feet a year. Hasencamp doesn’t think we necessarily have to explicitly close the structural deficit. 

“The entire Colorado River basin is out of balance and all states, all seven states and Mexico have to figure out how to permanently live with less water,” he said.

"I think there’s some balance where the priority system is recognized and Arizona maybe has to do a little bit more, but that all states and all water users have to be part of the solution." — Bill Hasencamp, Metropolitan Water District of Southern California


Buschatzke pointed out something else about the 1968 law: it says the federal government should look into augmenting the Colorado River. 

The  text of the law reads “the Secretary of the Interior shall conduct full and complete reconnaissance investigations for the purpose of developing a general plan to meet the future water needs of the Western United States.” It also requires periodic progress reports.

Buschatzke said the augmentation plan hasn’t happened.

“There’s never been a mechanism found to do that. That would certainly have changed the reliability of Arizona’s water supply, of all of our water supplies in Nevada, California and Mexico if that had been done,” he said. “It hasn’t been done.”

Fleck called the language in the law around augmentation “extremely weak” and said there’s an argument the feds have done enough already.

The most likely option for meaningful augmentation is desalinated ocean water. Investment in “desal”  has grown around the world, although it has significant environmental consequences

However it might be achieved, augmenting the river would be costly and a project for the long term.


Another way to close the structural deficit might be to reduce water use in a multitude of ways — something that’s already happening. The lower basin states are all  currently on track to use less than their full allocations this year. The question is whether those savings can be made permanent.

Ted Cooke, general manager of the agency that runs the Central Arizona Project, said Arizonans "know how to do this," even if closing the gap takes ideas that haven’t yet materialized.

“We’re really good at balancing those things in Arizona to have the lifestyle and the economic vibrancy that we enjoy by making sacrifices when we have to,” he said.

And Cooke said people need to remember the basics as Arizona plans for the future: We live in a desert, water is scarce, and the price is only going in one direction — and that's up. 

He isn’t alone in his optimism. Many water experts are somewhat hopeful about fixing the structural deficit, even those mindful of how hard water can be politically.

“If there’s any basin in the world that can solve this, I’m convinced it’s actually the Colorado River basin,” said Udall. “It’s the right size, it has people who know each other, it has years of good will. I mean that’s the good news here.”

Watering the West required optimism, engineering, and money. Sustaining it will, too. 

This story is part of Elemental: Covering Sustainability, a new multimedia collaboration between Cronkite News, Arizona PBS, KJZZ, KPCC, Rocky Mountain PBS and PBS SoCal.

Bret Jaspers was a senior field correspondent at KJZZ from 2017 to 2020.