Meager snowpack adds to Colorado River’s woes, straining flows to Southern California

Many of California’s reservoirs have filled nearly to capacity this year with runoff from the ample snowpack in the Sierra Nevada. But the situation is very different along the Colorado River, another vital water source for Southern California, where a very dry spring has shrunk the amount of runoff streaming into reservoirs.

The latest forecast from the federal Colorado Basin River Forecast Center shows that the river’s flows into Lake Powell probably will be about 46% of average over the next three months.

“We are noticing that runoff is low. There is no doubt about it,” said Luke Gingerich, a farmer who grows peaches near the river in Palisade, Colo.

The snowpack in the upper Colorado River Basin reached 89% of the median level April 1, but the outlook has worsened over the last two months because of persistent dryness, warm temperatures and dry soils in the mountains that have absorbed a portion of the runoff.

“This is another year that is not going to help the Colorado basin’s long-term water crisis. It’s going to make things worse,” said Daniel Swain, a UCLA climate scientist. “This year will once again be putting more stress on the Colorado system.”

The water level of Lake Powell, on the Utah-Arizona border, sits at 33% of capacity. Downstream near Las Vegas, Lake Mead is about 31% full.

With the meager snowmelt, the country’s two largest reservoirs probably will decline further this year, and could approach critically low levels that require additional cuts in water deliveries in the next couple of years.

Representatives of California and six other states have been negotiating long-term plans for reducing water use after 2026, when the current rules expire, to deal with the ongoing shortages. But disagreements over competing proposals have created a deep rift among the three states in the river’s lower basin — California, Arizona and Nevada — and the four states in the river’s upper basin — Colorado, Utah, Wyoming and New Mexico.

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The latest projections from the U.S. Bureau of Reclamation, which manages the river’s dams, show that the rest of 2025 “will be another very dry year and the consequences will be significant,” authors and water researchers Eric Kuhn and John Fleck wrote in a blog post.

Kuhn and Fleck said the latest federal figures reveal that despite ongoing conservation efforts — including programs paying farmers who agree to temporarily leave some of their fields dry — further declines in the reservoirs are expected. Recent estimates show “we are once again failing to rebuild reservoir storage,” they wrote. “We’re draining the system.”

The Colorado River provides water for cities from Denver to San Diego, 30 Native tribes and farmlands from the Rocky Mountains to northern Mexico.

The river has long been overallocated, and its reservoirs have declined severely since 2000. The average flow of the river has decreased about 20% since 2000, and scientists have estimated that roughly half that decline has been caused by global warming driven by the burning of fossil fuels and rising levels of greenhouse gases.

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In recent years, the states have adopted a series of incremental water-saving plans to try to prevent reservoirs from reaching perilously low levels — at times voicing fears that inaction might eventually drive Lake Mead to “dead pool,” a point at which water would no longer flow downstream past Hoover Dam.

At very low reservoir levels, there are also other risks. The states of the upper and lower basins have stated conflicting interpretations of a certain provision of the 1922 Colorado River Compact concerning how much water the upper basin must deliver to the lower basin over a 10-year period, which Kuhn and Fleck have described as a looming “tripwire” that might trigger a legal fight.

This year’s low runoff underscores the need for a new set of post-2026 river management guidelines, because the current rules aren’t preventing reservoirs from declining toward critically low levels, said John Berggren, regional policy manager for the nonprofit group Western Resource Advocates.

“What we’re seeing is the importance of a new set of guidelines for another 20 years that actually does respond to climate change, that does proactively prepare for these shortages, and does stabilize the system,” Berggren said.

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Southern California uses more water from the Colorado River than any other state, supplying cities and farmlands. Although the regional water shortage is likely to continue to drive conservation efforts, the Metropolitan Water District of Southern California has a record amount of water banked in reservoirs and underground storage areas, benefiting from supplies delivered during the last three years in California.

In the Colorado River Basin, April and May were very dry. Warmer-than-average temperatures in parts of the region have contributed to the diminished runoff.

“Increasing temperatures in recent decades are having a real impact on runoff,” Berggren said, describing this year’s projected runoff as similar to 2022, which also was one of the lowest in recent years.

“It’s something that, unfortunately, we’re going to see more and more of, where you need well above average snowpack to come somewhere close to average runoff because of the warming temperatures,” Berggren said. With the reservoirs at low levels and the inflows shrinking, he said, “we’re kind of on a knife’s edge between being OK and being in very scary, catastrophic situations.”

Scientists have determined that the last 25 years probably have been the driest quarter-century in western North America in 1,200 years, a severe megadrought that research shows is being intensified by rising temperatures.

As of last week, the U.S. Drought Monitor website shows that about 51% of 11 Western states are experiencing some level of drought, and that parts of the Colorado River Basin are in severe or extreme drought.

Although Southern California is classified as being in a drought, Northern California is not.

The state’s largest reservoir, Shasta Lake, is about 91% full. Lake Oroville, the second-largest reservoir, stands at 100% of capacity.

Although the Sierra Nevada has had average or above-average snow for the last three years, the snowpack has melted quickly this year because of dry conditions and warm average temperatures, especially warm nighttime temperatures in the mountains.

“Almost all the basins have melted out really fast,” Swain said, describing it as a signature of the warming climate.

“We are seeing earlier melt-out of western mountain snowpack, particularly at lower to middle elevations,” he said.

The latest seasonal forecast from the National Oceanic and Atmospheric Administration predicts that hotter-than-average temperatures probably will persist this summer across much of the West, including the Colorado River Basin and California.

The earlier snowmelt in many areas probably will mean that soils and vegetation in the mountains dry out earlier, which could lead to increased wildfire risks in the coming months, Swain said.

“The last few years, we’ve seen snowpacks so good at high elevations in California that there really hasn’t been a fire season” in high-elevation forests, Swain said. “So I think that we may see more fire activity as a result this summer compared to the last couple of years in the mountains.”