Storms fill California’s dangerously low reservoirs

Catastrophic storms dumping unprecedented amounts of rain across California have at least temporarily eased a years-long drought that has worried hydrologists and environmental scientists concerned with the future of America’s bread basket.

The storms, which have cost at least 19 people their lives and more than $1 billion in damages since late December, have poured millions of gallons into reservoirs up and down the state, and — perhaps more crucially — hundreds of inches of snow throughout the Sierra Nevada mountain range.

More than 13.5 inches of rain have fallen on San Francisco since Dec. 26. Sacramento received 9.5 inches over the same span. Water stations in the Northern Sierra region received about 60% more rain than average in December. Those stations have already received more rain in the first 12 days of January than is typical for the entire month.

Shasta Lake, north of Redding and the largest reservoir in California, rose to 44% capacity as of Wednesday, according to the California Department of Water Resources, one third higher than its level on Christmas Day, the day before successive waves of atmospheric rivers began soaking the state.

The lake, which sits on the Sacramento River, stood at 72% of its historical average on Wednesday. On Christmas, Shasta Lake was only at 55% of its historical average.

Lake Oroville, the second-largest reservoir in the state, had risen from 30% full on Christmas Day to 49% capacity as of Wednesday, a two-thirds increase.

Six reservoirs in the Central Valley, home to the most fertile agricultural land in the nation, were higher on Wednesday than historic averages, a mammoth sea change after years of drought threatened farms and communities across the state.

On Wednesday, more than two feet of snow fell across the entirety of the Sierra Nevada range. Snowpack in the Central and Southern Sierras stood at more than twice historical levels, while the amount of snow that has fallen in the Northern Sierras is nearly at 200% of normal.

The southern and central regions have already received more snow than averaged by April 1, when snowpack is typically at its deepest levels of the year. Snow levels are higher than they have been at any time in the last 20 years.

California emergency officials are still scrambling to get aid to communities hit hardest by the storms. Rain is expected to continue to fall through Friday, before a brief break in the weather over the weekend.

“We’re not out of the woods. We expect these storms to continue at least through the middle of next week with a minimum of three more atmospheric rivers hitting our state,” Gov. Gavin Newsom (D) said as he visited Capitola, near Santa Cruz, to inspect storm damage. “California is soaked and even an inch more of rain can bring catastrophic impacts like flooding and mudslides.”

The storms, Newsom said, have claimed more lives than have wildfires over the last two years. 

The water filling reservoirs and the snow falling in the mountains are at least temporary lifelines for a state that has seen drought over most of the last two decades. But that drought is also making it more difficult for California’s parched soil to replenish underground aquifers. Drier soil is less able to absorb large amounts of rainwater.

“This is a prime example of the threat of extreme flooding during a prolonged drought as California experiences more swings between wet and dry periods brought on by our changing climate,” Department of Water Resources director Karla Nemeth said last week, even before the latest round of severe storms, floods and mudslides.

Scientists hope the snowpack, in particular, will be a longer-term benefit to the state as it melts over the summer months. 

But experts cautioned that the rapidly rising reservoirs and the deep powder in the mountains is no guarantee of what the rest of the year will bring.

“It’s always great to be above average this early in the season, but we must be resilient and remember what happened last year,” Sean de Guzman, who manages snow surveys and water supply forecasting for the Department of Water Resources, said in a statement, referring to a disastrously dry start to last year.