California’s mountain snowpack is rapidly shrinking after the driest start to the calendar year on record and a late-March heat wave. Melting could accelerate with another heat wave next week.
But those gains have been lost.
On Friday, the California Department of Water Resources conducted its monthly snow survey at Phillips Station in the Sierra Nevada.
Standing in a nearly snow-free meadow, Sean de Guzman, manager of the department’s Snow Surveys and Water Supply Forecasting, measured only 2.5 inches of snow depth — only 4 percent of average for the date at that location.
“With below average rain and snow statewide, California is now facing a third consecutive year of dry conditions and extending this ongoing drought,” he said. “This past January, February and March have been actually the driest period on record in the Sierra Nevada dating over 100 years.”
And that's a wrap on March, and unfortunately another below normal precip month. The aggregate of the @CA_DWR 8, 5, and 6 station indices will finish as the driest "Jan+Feb+Mar" on record (back to 1922, 101 yrs) by a huge margin. Here are the 10 driest. #CAwx #CAdrought #CAwater pic.twitter.com/kM7PCNb2Jm— NWS California-Nevada RFC (@NWSCNRFC) April 1, 2022
Statewide snowpack now sits at 38 percent of average, about a third of where it should be this time of year. California is poised to enter a third consecutive summer in drought, with serious implications for water supply and wildfire in the months ahead.
“The conditions we are seeing today speak to how severe our drought remains,” Department of Water Resources director Karla Nemeth said on Friday, calling on all Californians to conserve water in the face of a third dry year.
The deficits are particularly striking in Northern California, where the state’s largest reservoirs are located and where extreme drought has re-emerged and expanded in recent weeks, according to the U.S. Drought Monitor.
“Northern California in particular did not get enough precipitation this year,” said Helen Dahlke, an associate professor of hydrology at the University of California at Davis. “We are supposed to be the water tower for the state.”
According to California State climatologist Michael Anderson, average snow water equivalent — the amount of water held in snow — peaked statewide on March 8.
Snowpack has historically peaked on April 1 — a milestone date for water resources in California and other parts of the West — after which it begins to melt because of the higher sun angle and increased solar radiation in spring. Under normal conditions, that melting should continue through the spring and well into summer, filling the state’s man-made reservoirs and moistening soils and plants.
Slow and steady melting doesn’t appear to be in the cards this year.
“We’ve already seen pretty significant melt this year, and we expect that to continue,” said Anderson, who works at the California Department of Water Resources.
The snowpack took an especially hard hit during a recent heat wave, with the Northern Sierra losing more than a quarter of its snow water content March 19-26.
Forecast models show an intense heat wave could build over the western United States next week. In fact, the Climate Prediction Center has placed a bull’s eye over California, signaling a very good chance for much-above-normal temperatures in early to mid-April.
The early snowmelt could mean that there will be less water available for irrigation and for fish downstream of reservoirs during the heart of the summer dry season. The landscape will also dry out sooner, even at higher elevations, leading to a prolonged stretch of abnormally parched conditions.
Current wildfire outlooks predict an early start to the large fire season, which this year is expected to ramp up in May in some areas.
Last year, after a warm and dry spring, the state’s snowpack hit the “zero” mark by late May, with consequences that included depleted reservoirs, water shortages, the shutdown of the state’s largest hydroelectric plant and devastating forest fires during the summer of 2021.
This year, snow could be gone by late April or even earlier, depending on the weather.
It remains unclear how much meltwater ultimately will make it to reservoirs, many of which are less than half full, including Oroville and Shasta, the state’s largest. In 2021, the snowpack was built on historically dry soils, which quickly absorbed the melting snow. This year’s wet start to the year boosted soil moisture before the snowpack was built in December, making it more likely that runoff will flow into streams and reservoirs.
The California Department of Water resources noted in a report published last year that, because of climate change, it has become “increasingly difficult to rely on historical observations to predict water supply conditions” and that the department’s “runoff forecasts substantially over-estimated the runoff that occurred” in spring 2021.
Dahlke said that computer models have become less reliable at predicting how much water will flow into streams and reservoirs, for a number of possible reasons. The state’s overgrown forests are probably using more water, which models may not be capturing, for example. Water is also being lost to evaporation and sublimation as a result of higher temperatures.
“It’s not clear what fraction of the snowpack is just disappearing into the atmosphere,” she said.
A study published last fall projects that persistent low-to-no-snow conditions in the Sierra and in the Mountain West could become the norm if climate change continues unabated.
In the western United States, climate warming has already brought substantial declines in mountain snowpack, with peak snow water equivalent dropping by about 20 percent since the 1950s, according to one study. It has also shifted the timing of snowmelt to earlier in the spring.
“The days when we had snowmelt occurring through June — those days are over,” Dahlke said.
Diana Leonard is a science writer covering natural hazards. You can follow her on Twitter @HazardWriter.