In a much-needed break after multiple years of severe droughts over the past two decades, California’s statewide Sierra Nevada snowpack, which provides nearly one-third of the state’s water supply, was at 96% of its historical average on Tuesday, up from 83% a month before.
The April 1 reading, considered the most important of the year by water managers because it comes at the end of the winter season, follows two previous bountiful years when the snowpack reached 111% of normal last year on April 1 and 237% in 2023.
Although Tuesday fell just short of a third year in a row above 100%, together the past three years represent most bountiful three-year period for the Sierra snowpack in 25 years. The last time there was this much snow three years in a row came in 1998, 1999 and 2000.
“Gosh, what a relief,” said Jay Lund, a professor of civil and environmental engineering at UC Davis. “We’re in good shape. This is one of the better years in recent decades. We’ve had quite a lot of good precipitation this winter, especially in Northern California. And we haven’t had any major flooding. It’s been a near-Goldilocks amount. Just right.”
California struggled with three severe droughts over the past generation: From 2007-2009, then 2012-2016, and most recently from 2020-2022. Brown lawns and water restrictions were the norm.
But the past three winters have shown how the state’s hydrology can vary widely.
That “weather whiplash” is being exacerbated by climate change, scientists say. Warming temperatures make droughts more severe and dry out soils and vegetation more intensely, increasing fire risk. But in wet years, when big atmospheric river storms come barreling off the Pacific, warmer conditions also can cause more water to evaporate into those storm systems, bringing more rain.
One big benefit of having multiple wet winters in a row is that the rain and snow, which melts in the spring and summer, fills California’s reservoirs.
Across the state, three years of productive winters have left nearly every major reservoir above its historic average. The biggest ones statewide averaged 117% of their capacity on Tuesday.
That’s despite the fact that during major storms in mid-February, reservoir operators increased releases of water significantly from some of the largest, such as Shasta and Oroville, to create room to catch more runoff and reduce the risk of flooding downstream.
All that water means most cities and suburbs across the state won’t have any water restrictions this summer, Lund noted.
“There will still be small communities in some rural areas with issues, but on the whole we probably should be more worried about complacency,” he said.
On Tuesday, Shasta Lake, the state’s largest reservoir, near Redding, was 89% full and rising. The second-largest — Oroville, in Butte County — was 88% full. San Luis Reservoir, east of Gilroy, was 89% 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 97% full.
Storms haven’t hit the state evenly. On Friday, the snowpack in the Northern Sierra was 118% of average, and in the Central Sierra it was 91%. But in the Southern Sierra, it was only 84%.
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 135% of average. San Francisco is at 96%, and San Jose is at 75%. But Los Angeles rainfall is at just 59% of normal.
As a result, Southern California counties from Santa Barbara to San Diego have been categorized in recent weeks as entering various levels of drought by the U.S. Drought Monitor, a weekly report put out by the federal government.
Lund noted that if half of California is going to be wet and the other half dry, it’s far more important to have a year like this one, when the north is wet. That’s because nearly all the major reservoirs are in the north.
Overall, California was in a drought for 11 years out of the 16 years between 2007 and 2022. Cities, counties, and state officials put in place major policies during those droughts that helped reduce the impact of future droughts.
They include voluntary programs to pay residents to replace their lawns with drought-tolerant landscaping; the construction of several new off-stream reservoirs such as Los Vaqueros in Contra Costa County and Diamond Valley in Riverside County; a landmark state law requiring more sustainable management of groundwater; tougher building standards requiring more water-efficient toilets, appliances, and industrial equipment; and a state law to encourage smaller, cash-strapped water districts to merge with larger ones.
“A year like this is a good time to prepare for the next drought,” Lund said. “We should be building projects, upgrading old facilities, and hiring new water engineers to replace the ones who retire. It’s like Benjamin Franklin said: ‘When the well’s dry, we know the worth of water.’”