Without significant, permanent cuts to water use in the Colorado River basin, both Lake Powell and Lake Mead may be headed for collapse.
That’s according to a new, peer-reviewed paper published in the journal Science this week that analyzed how current agreements between basin users would fare if the 23-year trend of below-average runoff in the basin continues.
The short answer is not well, despite layers of drought contingency plans that have been added in recent years to trigger increasing cutbacks for certain users as Lake Mead’s level drops.
“If this ‘Millennium Drought’ persists,” wrote the paper’s authors, which included a team of researchers from Utah State University’s Center for Colorado River Studies, Colorado State University and the University of Oxford, “then stabilizing reservoir levels to avoid severe outcomes will require reducing water use to match diminished runoff.”
That demand can’t continue to outpace supply without further draining Lake Powell and Lake Mead — which are both filled to 27% of capacity, down from 95% full in 2000 — is a fairly obvious point. It also is clear that the current drought planning measures won’t cut it alone since the federal government had to enact emergency actions last April to send more water than usual into Lake Powell.
“We haven’t acted fast enough,” said lead author Kevin Wheeler, a water policy consultant and fellow with Oxford’s Environmental Change Institute. “We’re in a position that all of the reaction has to be conservation by necessity.”
But how to best stabilize the system and protect hydropower generation at both reservoirs in the longer term is difficult, the paper stated, due to “complex water supply problems” that require a “deep understanding of the social and economic implications of any proposed policies.”
Part of a potential solution might lie in changing how water storage is measured in the basin.
The paper’s authors describe a new management approach where mandatory and voluntary cutbacks for water users would be triggered based on the combined storage of both Mead and Powell, rather than just Lake Mead as is currently the case.
Wheeler and his colleagues found that if the average hydrology of the 21st century continues, the status quo management paradigm will put the system at serious risk.
One of many possible solutions the team identified looked at what would happen to the reservoirs if the Upper Basin states of Utah, Colorado, Wyoming and New Mexico agreed to give up water development ambitions, while the Lower Basin states of California, Arizona and Nevada, along with northwest Mexico, agreed to reductions.
The paper found, in its analysis of one of several scenarios, that if the Upper Basin limited water use to 4 million acre-feet per year, or slightly above its average use since 2000, and the Lower Basin agreed to 2 million acre-feet in cuts each year going forward, then the system would be more likely to stabilize near current reservoir levels.
That scenario would require a sacrifice from the Upper Basin, which has plans to develop up to 5.4 million acre-feet of water annually by 2060, and a reduction in use by the Lower Basin and Mexico, which together use more than two-thirds of Colorado River water.
Wheeler acknowledged, however, that the paper used a model that assumed a continuation of average river flows since 2000, not a potentially catastrophic scenario such as a series of back-to-back, low-runoff years like the basin saw in 2002, 2020 and 2021.
If that happens, he said, “things could get much more precarious very quickly.”
More water cuts ahead
A kind of trial run for implementing a version of the cuts the paper analyzed is already underway in the basin.
Last month, Bureau of Reclamation Commissioner Camille Touton announced that the seven basin states had 60 days to present plans to protect reservoir levels by making between 2 and 4 million acre-feet in water cuts by next year. Touton added that the federal government is prepared to make the reductions if the states cannot agree to a plan.
On Tuesday, the Upper Basin states, including Utah, sent a letter to Reclamation outlining a five-point plan that could limit water use through considering programs to increase water monitoring and efficiency, to pay farmers who voluntarily agree not to irrigate in certain years, and to develop an updated drought response plan.
The letter emphasized that the Lower Basin would have to bear the majority of the reductions.
“Lower Basin uses are more than double those of the Upper Division States, and any cuts we make have to reflect that,” said Amy Haas, executive director of the Colorado River Authority of Utah. “Along with our Upper Division State partners, Utah has taken significant, measurable steps to optimize our water usage and protect the critical infrastructure at Lake Powell but there has to be a balanced approach that reflects that reality.”
Environmental groups blasted the letter for failing to offer concrete, immediate cuts and for not mentioning the numerous projects that have been proposed in the Upper Basin to divert more water from the overtaxed river.
Gary Wockner, of Save the Colorado, called the five-point plan “meaningless gibberish.”
“It was a nothing burger with a side of hot air,” said Zach Frankel, executive director of the Utah Rivers Council. “There needs to be a good-faith effort to reduce water use across the whole basin.”
Frankel added that if the Upper Basin is unwilling to make immediate reductions, it should at least offer to take future projects like Utah’s Lake Powell Pipeline off the table, which he called a “fantasy that needs to be put to bed.”
The paper in Science noted that any additional consumptive uses in the Upper Basin will decrease inflows into Lake Powell and Lake Mead.
“Lower Basin users have indicated that they are unlikely to reduce their uses to stabilize reservoirs only to see new upstream uses nullify these conservation efforts,” Wheeler and his colleagues wrote.
The paper also said that the Upper Basin is required to send a set amount of water downstream under the Colorado River Compact of 1922, while noting there are conflicting interpretations of the compact that have yet to be settled.
“A fixed delivery requirement under declining flows puts the entire burden of climate change on the Upper Basin,” they wrote.
“We tried not to pick on one basin or the other,” Wheeler said. But he added that water managers should be planning for a possible continuation of the Millennium Drought, which as reduced Colorado River flows by an average of 20% compared to the previous century’s average.
“The science on aridification is pretty solid, and we need to be prepared for that,” he said.