California’s snowpack is supposed to reach its peak April 1, so today, state surveyors hold their final Sierra snow survey of the year.
But instead of peak snow, there’s almost none.
Snow across California’s Sierra Nevada measured just 18% of average Monday — among the smallest in decades. A month of record-shattering heat thawed the snow and sent runoff coursing into streams and rivers, leaving only minimal water in the mountains as the state heads into dry season.
The early melt is a symptom of global warming that scientists say is becoming more pronounced.
“This particular year is as clear an indication of the influence of climate change as anything we’ve seen,” said Peter Gleick, a leading water scientist and co-founder of the Pacific Institute. “Climate change is influencing California’s water system quickly and severely.”
This year the Sierra snowpack peaked on Feb. 25 at 73% of average.
The summerlike heat in March broke monthly records in many areas of the Western U.S., accelerating the melting of snow in the Rocky Mountains as well.
Precipitation in California has been about average since October, but more of that precipitation is falling as rain, less as snow.
The warmth and premature melt mean the state’s forests will dry out a month or more earlier than usual, Gleick said, which increases the risk of wildfires.
“It also means rivers and streams are going to dry out sooner, and that has bad implications for natural ecosystems and our fisheries,” he said.
Cities and farms should still have have ample water because major reservoirs in Northern California are nearly full. That’s because this winter brought decent rain and the three years prior years were wet, too.
“We were lucky this year in the sense that even though we have so little snow left, we had an average amount of rainfall,” Gleick said. “There are going to be years, inevitably, where we not only have almost no snow, but we don’t get the rain either.”
California traditionally had relied on the Sierra snowpack to hold about 30% of its water, on average.
“We’re losing that storage,” Gleick said. “If we can’t depend on reliable long-term snowpack and snowmelt later in the year, we’re going to have to do other things to make our water system more resilient.”
When Gleick wrote his dissertation at UC Berkeley in the 1980s, he examined a range of climate scenarios and analyzed how rising temperatures would likely change the timing of runoff in Northern California.
“Current trends precisely match scientific projections from decades ago,” he said. “More and more of our annual runoff is occurring in the winter months, and that’s because it’s more rain, less snow and faster snow melt.”
Adapting to these changes requires new thinking and new approaches, he said, including efforts to use water more efficiently, recycle more wastewater, capture more runoff to replenish groundwater, and change how reservoirs are operated.
Though California isn’t in a drought, dry conditions have spread in parts of the state. It’s now abnormally dry in about one-fourth of California, largely in the northeast, according to the U.S. Drought Monitor website.
At UC Berkeley’s Central Sierra Snow Laboratory, near Donner Pass, only patchy snow remains.
“This year is a perfect example of warm snow drought,” said Andrew Schwartz, the lab’s director. “We’ve seen a lot of rain that would have been snow if we had cooler temperatures.”
There have been worse years, Schwartz noted, including during a severe drought in 2015, when the sparse snow disappeared around the lab even earlier.
What stood out about this winter was the off-the-charts warmth. Daniel Swain, a climate scientist with UC Agriculture and Natural Resources, described it as one of the most “extreme heat events ever observed in the American Southwest.”
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