Millions in the West face low water supply

Lake Powell’s water levels remain under pressure heading into summer after a disappointing snow season across much of the Colorado River Basin, raising fresh concerns about water supplies in the Colorado River System, one of the nation’s most important river systems.

The reservoir, which straddles the Arizona-Utah border, depends heavily on spring runoff from mountain snowpack. But this year’s snow season never fully developed across many parts of the West, limiting the amount of water flowing into the Colorado River and its major reservoirs.

Lake Powell and Lake Mead, two of the largest reservoirs that feed the Colorado River system, are both sitting critically low. This week, Lake Powell’s elevation is right around 3,527 feet above sea level, which is only about 158 feet away from “dead pool.” This is the threshold at which the Glen Canyon Dam can no longer generate hydropower. 

This is dangerously close to Lake Powell’s record low of 3,520 feet that occurred in April of 2023. 

“One of the really noteworthy parts of the last six months or so has been the demise of the western snowpack, and so there’s just not very much to draw upon,” said Dan Cayan, a climate researcher at the Scripps Institution of Oceanography at the University of California, San Diego.

The timing is especially problematic because the annual runoff season is largely coming to an end. Water managers typically rely on melting mountain snow during spring and early summer to provide the largest inflows of the year to Lake Powell and downstream reservoirs. 

Many regions across the West have one of their thinnest snowpacks on record, leaving not much for runoff in the spring and summer.

“The chances to recover are in the cool-season snowpack-driven stream flows, and of course, we’re pretty much past that,” Cayan said.

While individual years can bring swings between wet and dry conditions, the Colorado River Basin has been grappling with a much longer-term problem. Cayan noted that the basin has experienced an unusually high number of dry years since the late 1990s, a period often referred to as the Southwest’s megadrought era.

Compounding the issue are rising temperatures. Even when precipitation falls, warmer conditions can reduce the amount of water that ultimately reaches rivers and reservoirs. More moisture evaporates from soils and water bodies, while plants consume more water during hotter growing seasons.

“The Colorado system really is sort of a canary in the coal mine for climate warming stress,” Cayan said.

This year delivered what he described as a “double whammy” across much of the West: below-normal precipitation combined with unusually high temperatures. The result was reduced snow accumulation and diminished runoff into major reservoirs.

Will the West run out of water?

Lake Powell and downstream Lake Mead are critical components of the Colorado River system, which supplies water to 40 million people across seven Western states, while also supporting agriculture, industry and hydroelectric power generation.

Although many locations rely on multiple sources for water, some communities don’t. Remember East Porterville, California, in 2014? They completely ran out of water and had to rely on bottled water and outdoor storage tanks.

“I think there are a lot of people and sectors that are extremely concerned right now because of these dwindling water supplies,” said Cayan. “There are certain threshold points on these big reservoirs, where you get below the point where you can deliver water, or whether water can be used for electrical generation, and there are things like that that are a great concern.” 

Some relief could arrive later this summer. The development of a strong El Niño could work in the West’s favor. A strong El Niño typically boosts the monsoon season, which could bring beneficial rainfall to parts of the Southwest. 

Still, even a monsoon boost is unlikely to provide the type of large-scale recovery that the Colorado River system needs.

“It really awaits heavy winter seasons and snowpack to substantially recover from these deficits,” Cayan said.

The coming months will likely bring increased attention to the fate of Lake Powell and the broader Colorado River Basin. Water managers, farmers, utilities and communities throughout the Southwest will be watching closely to see how far the river system’s water can stretch.

However, even if wetter years return, scientists say a warming climate means the basin is becoming less efficient at converting precipitation into runoff, adding another challenge to the long-term effort to secure water supplies across the West.