As a megadrought continues, new projections show a major Colorado River reservoir could sink to rock bottom later this year

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The cuts would be triggered on the terms of drought contingency plans signed by the seven Colorado River Basin states in 2019 in an effort to stabilize the river system.

Despite the agreements, Lake Mead is only 39% full today. And Lake Powell, the river’s second largest reservoir, is only 36% full, according to an April water supply report.

The reservoirs along the river system have been constructed as a buffer to store water and to ensure a reliable supply even in times of drought. But experts say that due to climate change and a 20-year drought, more water is now being extracted from the river system than flows into it, causing levels in these important reservoirs to drop.

“This shows us that the kinds of dire scenarios that we have been preparing for and hope will not happen are now here,” said John Fleck, the director of the University of New Mexico’s Water Resources Program.

The Colorado River provides water to 40 million people in seven western states and Mexico, irrigating more than 5 million acres of farmland as it makes its way from the Rocky Mountains to the Gulf of California.
The water release reductions that could begin next year would be felt in Arizona, Nevada and Mexico, but Arizona would be hardest hit by the cuts, under the terms of the drought contingency plan signed by these three states, which form the lower catchment area. . The states of Wyoming, Utah, Colorado, and New Mexico in the upper watershed have agreed to a separate plan calling for voluntary water conservation measures to prevent Lake Powell from also reaching a critically low level.
As part of the lower basin drought contingency plan, the Central Arizona Project – a massive 336-mile canal and pipeline system that carries Colorado River water to Phoenix, Tucson and farms and towns in between – would see water supplies decline. about a third in 2022 because of its junior rights to the water of the river.
The effects of those water savings will be most acutely noticeable on farms in central Arizona, due to their lower priority in a complex tier system used to determine who loses water first in the event of a shortage.
The Central Arizona Project Channel runs through the rural desert near Phoenix. Some farmers who receive Colorado River water from the Central Arizona Project may see their supplies slashed as early as next year.
In a joint statement last Thursday, the Arizona Department of Water Resources and the CAP acknowledged the new projections and impending cuts, but said the state is prepared.

“The study, while important, is no surprise,” the statement read. “We are prepared for these conditions, in large part thanks to Arizona’s unique collaborative efforts between water leaders, including tribes, cities, agriculture, industry and environmental organizations, who have developed innovative conservation and mitigation programs as part of the implementation of the Drought Contingency Plan.”

One of the farmers standing to see its water supplies diminish is Dan Thelander. Together with his son, brother and cousin, Thelander grows cotton, alfalfa and other crops on 6,500 acres in the desert of Pinal County, Arizona.

With less water expected to be available to him next year, Thelander said he will likely have to set aside 30 to 40% of his land or leave it undeveloped.

Dan Thelander grows cotton, alfalfa and other crops in the desert of Pinal County, Arizona. He, along with other farmers in the region, is allowing their supply of water from the Colorado River to be significantly reduced as early as next year.

“We will have to fire workers. We will not buy that many seeds or fertilizers or tractors, and so we will just have to downsize and run a smaller farm,” Thelander said. “And yes, it will hurt a lot.”

Many farmers in Central Arizona, such as Thelander, have known for years that their supply of water from the Colorado River would eventually be phased out.

As part of a 2004 settlement between the federal government and the Central Arizona Project over debt issues, farmers in some Central Arizona irrigation districts agreed to give up their water rights in exchange for receiving water at a lower cost in the year 2030.

But with Lake Mead’s water level still near record lows and expected to decline further, the supply of that water could end years earlier than farmers expected.

Many factors contribute to the dwindling supply of the Colorado River system.

First, experts say more water is diverted from the river than enters the system.

The Colorado River wraps around Horseshoe Bend near Page, Arizona. A study from last year found that the river's flows have decreased by about 20% over the past century, largely due to climate change.

“It’s a math problem – Lake Mead normally releases 10.2 million acre-feet of water per year, and 9 million acre-feet flows into it,” said Brad Udall, a senior water and climate researcher at Colorado State University. “At some point, because you have a 1.2 million acre foot deficit every year, you have to fix it or else you’re draining the reservoir.”

In addition to that structural deficit, a historic drought and climate change are also undermining the river’s supply.

Much of the Colorado River Basin has fallen under the spell of what some scientists have called a megadrought over the past two decades.

The period from 2000 to 2018 was the driest 19-year trajectory the southwestern United States has seen since the 16th century, according to an analysis of tree ring data published in the journal Science in 2020. The scientists also found that the man-made climate crisis could be are attributed to nearly half the severity of the drought.
Another study by scientists at the US Geological Survey published in 2020 found that the flow of the Colorado River has decreased by about 20% over the past century and more than half of that decrease can be attributed to warming temperatures in the entire pelvis.

Most of the river’s flow comes from snow falling high in the Rocky Mountains of Colorado and southern Wyoming, said Chris Milly, a research hydrologist with the US Geological Survey and a co-author on the study.

Warming temperatures lead to a decrease in snowfall and an earlier melting of snow. But the sooner the snow melts and leaves bare ground, more heat energy from the sun is absorbed by the exposed soil. The warmer soil leads to more evaporation, which means less runoff from melting snow gets into the river, Milly said.

“Evaporation causes the catchment area to cool itself,” said Milly. “And so if you have more evaporation, you have less water to go down the river.”

Current conditions also don’t look promising for the kind of above-average runoff needed this year to start replenishing the river’s major reservoirs.

After an exceptionally hot and dry 2020, precipitation remained well below normal for much of the basin.

According to Paul Miller, a service coordination hydrologist at the National Oceanic and Atmospheric Administration’s (NOAA) Colorado Basin River Forecast Center, soil moisture in the region is also among the lowest on record.

This means that much of the melting snow carried off during the summer is likely to be absorbed by thirsty soils and plants before it can even reach the river, Miller said.

To Fleck, all this suggests that the diminished flows in recent years are likely not an anomaly, but rather a glimpse of the challenges of a warmer, drier climate.

“We now see the model for what the future of Colorado River Basin’s water use looks like, where scarcity is the norm and drought is not something special in the short term,” he said. “This is the way of life we ​​are in now, as climate change diminishes the flow on the river.”

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