It’s been a hydrological roller coaster ride this winter: Big storms followed by weeks of dry weather. But the water outlook across Northern California remains healthy for the summer, experts said Friday, with reservoirs brimming and summer water restrictions for Bay Area residents unlikely for the third year in a row.
The statewide Sierra Nevada snowpack, which provides nearly one-third of California’s water supply, was at 85% of its historical average Friday.
That’s up from 69% a month ago. And more storms are forecast for the next 10 days.
“We have gained over the month of February,” said Andy Reising, manager of the Snow Surveys and Water Supply Forecasting Unit at the state Department of Water Resources. “That’s good news. We had a bunch of good storms. They didn’t accumulate as much as we had hoped but nonetheless we’ll take what we can get.”
The Sierra Nevada acts as a giant frozen reservoir in winter, piling up snow over hundreds of miles, which then melts during spring and summer months, flowing down rivers and filling reservoirs with water for cities and farms. In winters when snow levels are below average, there is less runoff, which can lead to water shortages after several dry year in a row.
California has struggled with three severe droughts over the past generation: From 2007-2009, then 2012-2016, and most recently from 2020-2022.
But the past two winters have seen above-average rain and snow levels. If the Sierra snowpack grows to 100% or more of its historic average by April 1, it will mark the first time in 25 years with three average or above-average years in a row. The last consecutive trio of wet winters came in 1998, 1999 and 2000.
“So much of the past has been spent worrying about the drought,” said Andrew Schwartz, lead scientist at the UC Berkeley Central Sierra Snow Laboratory, near Donner Summit. “But now we are in a situation that comes across maybe once every 25 years or so. It’s something to be celebrated for sure.”
Water agencies in the Bay Area are similarly upbeat.
“Things look great,” said Matt Keller, a spokesman for the Santa Clara Valley Water District, which provides water to 2 million people in Santa Clara County.
“We know that drought years will be coming back and we have to be prepared for that,” he said. “But right now, reservoirs around the state are looking good and our groundwater supplies are looking good too.”
Keller noted that the San Jose district’s nine reservoirs on Friday were at 114% of their historical average, not counting Anderson Reservoir, near Morgan Hill, which is nearly empty for earthquake upgrades. Groundwater levels in Santa Clara County are at historically healthy levels after being recharged the past three winters.
“There are no talks of water restrictions this summer,” he said. “Our water supply looks healthy right now.”
Similarly, in the East Bay, the seven reservoirs owned by the East Bay Municipal Utility District were 81% full Friday.
Across the state, three years of productive winters have left nearly every major reservoir above its historic average. That’s despite the fact that during big storms in mid-February, reservoir operators increased releases of water significantly from some of the largest, like Shasta and Oroville, to create room to catch more runoff and reduce the risk of flooding downstream.
On Friday, Shasta Lake, the state’s largest reservoir, near Redding, was 78% full and rising. The second-largest — Oroville, in Butte County — was 84% full. San Luis Reservoir, east of Gilroy, was 82% full. To the south, Diamond Valley, a major off-stream reservoir in Riverside County that is key to water supplies in Los Angeles and surrounding cities, was 98% full.
Storms haven’t hit the state evenly. On Friday, the snowpack in the Northern Sierra was 104% of average, and in the Central Sierra it was 80%. But in the Southern Sierra, it was only 70%.
Rainfall totals this winter have been even more lopsided. The farther north that communities are located, the more rain they have received. Since Oct. 1, Santa Rosa rainfall totals have hit 147% of average. San Francisco is at 103%. San Jose is at 73%. But Los Angeles rainfall is at just 52% of normal.
As a result, Southern California counties from Santa Barbara to San Diego have been categorized in recent weeks s entering various levels of drought by the U.S. Drought Monitor, a weekly report put out by the federal government.
None of the nine Bay Area counties, however, or any part of California north of Modesto to the Oregon border is listed as currently experiencing drought conditions.
Several new storms are on the horizon. Light rain is forecast for early Sunday morning across the Bay Area, with up to 1 foot of new snow expected in the Sierra by Monday.
The National Weather Service issued a winter weather advisory from 10 pm Saturday to 1 pm Sunday, forecasting snow above 4,500 feet across the Sierra.
Computer models show more rain likely Wednesday, with the possibility of at least one atmospheric river storm on March 8 and 9 which has the potential to bring heavy snow. But it’s still early.
Schwartz said there is currently 6 feet of snow on the ground outside his mountain lab 12 miles northwest of Lake Tahoe.
“It’s looking like more of a persistent storm pattern might be opening up in about 10 days,” he said. “It could still change. But that’s fairly promising. If that happens the snow pack might hit 100% of average by April 1.”