‘We got unlucky.’ Why melting Sierra snow won’t save California from extreme drought

California’s drought conditions have gone from bad to worse in scarcely a month.

In the weeks following April 1, the traditional end of the rainy season, warm temperatures have burned off most of the Sierra Nevada snowpack and left the state’s water network gasping. Instead of delivering a generous volume of melted snow into California’s rivers and reservoirs, the snowpack has largely evaporated into the air or trickled into the ground.

“We got unlucky. A lot of it didn’t make it into the reservoirs,” said Jeffrey Mount, a geologist and water expert at the Public Policy Institute of California.

The miserly output from the Sierra Nevada helps explain why the U.S. Drought Monitor, a weekly hydrological analysis by the federal government, shows 93% of California in either “severe,” “extreme” or “exceptional” drought. A month ago, only about two-thirds of the state was facing those conditions.

The rapidly worsening drought has led to even sharper cutbacks in allocations to those who depend on California’s elaborate complex of dams, reservoirs and canals for their water.

Many farmers in the Sacramento Valley had been counting on getting a 5% allocation this year from the federal government’s Central Valley Project. On Wednesday, the Bureau of Reclamation put that meager shipment on hold, explaining that the melting snow wasn’t contributing much to the reservoirs.

The announcement was particularly bad news for Sacramento Valley rice farmers, who produce 97% of the state’s rice crop. Although many Valley farmers have special contractual rights that will give them enhanced deliveries from the Central Valley Project, every grower is facing a minimum 25% reduction, said Jim Morris, spokesman for the California Rice Commission.

Morris said farmers expect to plant 400,000 acres of rice this spring, leaving about 100,000 acres fallowed because of the water shortages.

That will depress the Valley’s rural economies, where unemployment rates range between 7.3% and 15.4%. It will also hurt the Pacific Flyway, the migration route for millions of geese and other waterfowl that depend on rice fields for nourishment.

“There’s a lot of impact beyond the amount of rice grown,” Morris said.

The increasing severity of the state’s water condition could ramp up the pressure on Gov. Gavin Newsom to declare a statewide drought emergency. So far the governor has resisted issuing such an order. Instead he has issued a regional emergency covering Sonoma and Mendocino counties, reflecting dire conditions on the Russian River.

California’s vanishing Sierra snowpack

Conditions were already bad when the rainy season ended in early April, capping a second straight dry winter. Sierra snow levels were just 59% of average.

The Sierra Nevada snowpack can provide up to 60% of the state’s water and is particularly important in summer and fall, when there’s no rainfall.

In a normal year, the snowpack “hopefully runs off in a predictable manner” and replenishes the state’s reservoirs as hot weather sets in, Mount said.

This year, though, a combination of factors has meant very little runoff has reached the reservoirs. Among other things, “the soils are so dry this year that the water’s not making it into the rivers,” Mount said.

And there’s very little snow left in reserve. While the spring hasn’t been scorching hot, it’s been warm enough that much of the snowpack is gone, with a fair amount of it evaporating, Mount said.

Scientists are struck by “how little of the snowmelt is turning into runoff,” Mount said. “It’s going back into the atmosphere.”

As of Friday, the snowpack was just 10% of average for early May, according to measurements taken by the state Department of Water Resources.

The reservoirs are suffering as a result. Folsom and Oroville lakes are holding about half as much water as they should for this time of year. Shasta Lake, the largest reservoir in California, is at 57% of average.

Which means it’s shaping up as a rough summer.

“It’s a pretty challenging year,” said Morris of the Rice Commission.

This story was originally published May 8, 2021 at 5:00 AM with the headline "‘We got unlucky.’ Why melting Sierra snow won’t save California from extreme drought."