Sierra Nevada snowpack ‘unusually normal’ and reservoirs are brimming as winter season winds down
As winter conditions wind down, the beginning of April is always the most important time for California’s water managers to take stock of how much snow has fallen in the Sierra Nevada.
This year, something unusual happened. After years of extreme drought and several very wet flood years, the Sierra snowpack, the source of one-third of the state’s water supply, is shockingly average this year: 104% of normal on Friday.
And more is on the way. The National Weather Service on Friday declared a winter storm warning for the Sierra, predicting 1 to 2 feet of new snow through Sunday. Chain controls went into effect on Interstate 80 Friday afternoon.
For a state where 11 of the past 17 years have been in severe drought, where massive, punishing storms last year brought the biggest snowpack since 1983 and waves of destruction along the coast, and storms in 2017 caused $100 million in flood damage to downtown San Jose and nearly collapsed Oroville Dam, an ordinary winter is a godsend, experts said Friday.
“It’s about as normal as you can get,” said Jeffrey Wood, a meteorologist with the National Weather Service in Sacramento. “It’s what we hoped for. In recent years we’ve had extremes. This year is definitely an outlier, but in a good way. Enjoy the normal.”
The last time California had a winter this close to the historical average was more than a decade ago, in 2010, when the Sierra snowpack on April 1 was at 104%. By comparison, last year on April 1 it was 232%. The year before, just 35%.
Two years of ample snow and rain have wiped away drought conditions. Most of California’s big reservoirs are brimming.
They were already full from last year’s bounty and have been topped with storms this year. The largest reservoirs in California on Friday were a combined 116% of their average capacity for the end of March, with the two largest, Shasta, near Redding, and Oroville, in Butte County, at 91% and 87% full.
The conditions mean that cities will not impose water restrictions this summer.
“This is a usefully boring year,” said Jay Lund, a professor of civil and environmental engineering at the University of California, Davis. “It will be useful if people use the lack of urgency to work on long-term preparations for both floods and droughts. That would be time well spent.”
The snowy February and March, along with healthy rain levels across the state, mean that California’s fire season this year could end up being another mild one.
“We might expect something similar to last year,” said Craig Clements, director of the San Jose State Fire Weather Lab. “Below normal in terms of acres burned. More snow. More moisture. Higher soil moisture. And higher fuel moisture levels. Things can change if we get a big heat wave in August. But for now all the rain and snow have helped a lot.”
Last year, following the wet winter, 324,917 acres burned statewide, according to Cal Fire, well below the state average for the previous five years of 1.7 million acres and more than 90% less than the horrific fire year of 2020 when 4.2 million acres burned statewide.
The shifting risk levels don’t mean that climate change isn’t happening, experts say. The Earth continues to warm, which makes droughts more severe. And that warming can cause winter storms to carry higher levels of moisture because more water evaporates from the ocean into them during hotter conditions.
But this year and last serve as a reminder that every year isn’t a wildfire Armageddon, Clements said.
“You are going to have some normal seasons,” he said. “You are going to have wet seasons.”
Few barometers of the state’s changing water fortunes are as dramatic as the weekly reports from the U.S. Drought Monitor, put out by the U.S. Department of Agriculture, the National Oceanic and Atmospheric Administration, and the University of Nebraska-Lincoln.
At the end of March 2022, 100% of California was in a drought, according to the monitor. Water shortages were prevalent around the state. A year later, just 28% of California was in a drought – mostly near the Oregon state line and in the southeastern corner of the state. This week? None of the state is in drought.
Early on it wasn’t clear what this winter would bring. On Jan. 1, the statewide Sierra snowpack was just 21% of normal. But steady storms through February, and particularly in the first week of March, brought the turnaround as the Sierra was blasted with 8 to 10 feet of new snow in blizzards that closed ski resorts and blocked I-80 and Highway 50.
Lund, the UC Davis professor, who described this winter as “unusually normal, said California still has significant water challenges, particularly in agriculture. State officials and farmers need to do a better job capturing water from storms and diverting it to recharge groundwater, he said.
In other areas, such as the Tulare Basin in the San Joaquin Valley, groundwater has been so heavily over pumped for decades that some acres will need to be taken out of production, he said.
Gov. Gavin Newsom has pushed hard for construction of the largest new reservoir in California in 50 years, Sites Reservoir, a $4.5 billion off-stream project proposed for Colusa County that would divert water from the Sacramento River in wet years for use in dry years. This month, the project received $205 million from the Biden administration and now has more than 90% of its funding. Whether it can break ground depends largely on if it can secure water rights later this year from the State Water Resources Control Board and overcome lawsuits from several environmental groups that say the water diversions could harm fish species in the Delta.
On Tuesday, state officials are expected to take a manual snow survey near Sierra-at-Tahoe ski resort. Friday’s statewide totals are expected to increase from this weekend’s storms.
“Winter is not over,” said Wood, the meteorologist. “It’s not abnormal to have an early spring system like this, and it’s definitely not the end of potential wet weather for the area. We will get some significant snowfall out of this one.”