Across the Bay Area and California, the past two weeks of soaking storms have brought mudslides, floods and power outages. They’ve also brought something not seen in years: Billions of gallons of water rushing into reservoirs, renewing hopes that the state’s relentless drought may come to an end this spring.
Six atmospheric rivers storms since the end of December have dumped half a year’s worth of rain on San Francisco, Oakland, Sacramento and other Northern California cities in two weeks. The ferocious weather has saturated soils, while also smothering the Sierra Nevada in snow, leaving the statewide snowpack Wednesday at a breathtaking 226% of its historical average and setting up reservoirs to receive more water when it melts later this spring.
“There’s no getting around it. This is great for reservoir storage,” said Jeffrey Mount, a professor emeritus at UC Davis and senior fellow at the Public Policy Institute of California’s water center. “It will clearly help the drought. We are likely to have full reservoirs this spring because there’s such a huge snowpack.”
Since Dec. 1, California’s 154 largest reservoirs have gone from 67% of their historical average capacity to 84% now, adding roughly 4.7 million acre feet of water in six weeks — or enough for the annual consumption of 23 million people.
The state’s largest reservoir, Shasta, near Redding, which is 35 miles long, has risen 37 feet since Dec. 1. The second largest, Oroville, in Butte County, has risen 95 feet, barely a year after state officials shut off the hydroelectric turbines in its dam for the first time in its 50-year history due to extremely low water levels.
“We’re all ecstatic,” said Lesley Nickelson, owner of Oroville Cycle, a store that sells boating and motorcycle equipment a few miles from Oroville Dam. “The marina has been way down at the bottom of a dirt hill for the past few years. People haven’t been going out on the lake. Now the boat ramps are underwater again. People are going back.”
The turnaround in some areas is stunning. On Monday, Lake Cachuma, the largest reservoir in Santa Barbara County, was 37% full. By Wednesday, following a pounding atmospheric river storm, it was 80% full.
Some reservoirs, like Folsom northeast of Sacramento, or Millerton, near Fresno, have risen so fast that their operators are releasing water to free up space and reduce flood risk for homes and businesses downstream.
“When there is storm after storm, we’re trying to make sure we are ready and prepared,” said Kristin White, Central Valley Operations director for the U.S. Bureau of Reclamation, which operates Folsom and Millerton.
To be sure, many of California’s biggest reservoirs are steadily rising but are still a long way from being full. On Wednesday, Shasta was 42% full, up from 31% on Dec. 1, but still only 70% of its historic average for that date. Oroville was 47% full Wednesday, up from 27% on Dec. 1, and now is 88% of its historical average.
Last year, a very wet December gave way to the driest January, February and March in a century, drawing the state back into drought after raising people’s hopes.
“We are certainly tracking better than last year,” said Molly White, operations manager of the State Water Project. “So far so good. This winter is on a good trajectory. We’ll see what happens in the next few months.”
State and federal officials caution that unseasonably hot weather in the coming months could melt much of the snowpack, or strong high pressure ridges could block new storms.
“Last year the spigot turned off,” White said. “It does rain in droughts. We need to be patient to see how the winter unfolds.”
This week, many smaller local reservoirs had already filled completely.
In Marin County, all seven reservoirs operated by the Marin Municipal Water District were 100% full for the first time in four years. Similarly Loch Lomond Reservoir near Ben Lomond in the Santa Cruz Mountains, which provides water for nearly 100,000 people in Santa Cruz, began spilling Sunday.
The seven reservoirs operated by the East Bay Municipal Utility District were 84% full Wednesday and rising. All three agencies said they do not expect to impose water restrictions or fines this summer.
“This is a relief. We have been waiting for these kind of storms for years now,” said Nelsy Rodriguez, a spokeswoman for East Bay MUD, which serve 1.4 million people in Alameda and Contra Costa counties. “It’s fantastic news after the last few years of non-stop bad news.”
In Silicon Valley, four of the 10 reservoirs operated by the Santa Clara Valley Water District are at or near 100% full — Almaden, Coyote, Chesbro and Uvas. But the district’s entire system is only 51% full because its largest reservoir, Anderson, near Morgan Hill, was ordered drained in 2020 by federal dam safety officials to complete a $1.2 billion earthquake safety project.
“We’re seeing a big boost to the reservoirs,” said Matt Keller, a district spokesman. “But the fact that Anderson is down is a real issue obviously for our local water supply. We are relying a lot on groundwater and imported water.”
As the climate continues to warm, scientists say more severe dry periods, followed by intense wet years, are becoming the norm. Eight of the past 11 years in California have been drought years. A study last year from Columbia University found that the last 22 years were the driest 22-year period in the American West in 2,000 years.
California must do a better job of capturing water in wet years to reduce the impacts of dry years on cities, farms, fish and wildlife, experts say.
“We have shifted into a pattern where we have to be much more careful about our use of water,” Mound said. “We need to do more sock away water in the wet years.”
The state should build more stormwater capture projects, as Los Angeles is doing, fund more projects to flood fields and orchards to recharge groundwater, and construct more off-stream reservoirs, Mount said.
Tim Quinn, a former water fellow at Stanford University who also ran the Metropolitan Water District of Southern California, agreed.
“We need to build it into our minds that we live in a state that is in a continual state of drought, punctuated by occasional very wet periods,” Quinn said. “How do we take advantage of the wet years?”
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