Sierra Nevada snowpack begins 2020 in good shape

Big storms around Thanksgiving boosted totals to 90% of historic average

After a dry start to California’s winter rainy season, a series of big storms that began around Thanksgiving delivered enough snow for the Sierra Nevada to begin 2020 in relatively good shape.

As of Thursday, the statewide Sierra Nevada snowpack — a major source of California’s water supply — stood at 90% of its historical average.

That’s the highest total in early January in four years, when it came in at 101% on Jan. 2, 2016.

“It’s a good start,” said Chris Orrock, a spokesman for the state Department of Water Resources. “It’s better than it was last year. But it’s still early. We’re cautiously optimistic.”

Last year on Jan. 2, the statewide snowpack was just 69% of normal.

Officials from the state Department of Water Resources conducted their first Sierra Nevada snowpack survey of the season, with the media in tow, at Phillips Station along Highway 50 near Sierra-atTahoe ski resort in El Dorado County.

At that location, the snow was 33 inches deep. Its water content was 97% of the historical average for early January. Readings at that site dating back to 1941.

How much snow falls every winter is critical to California’s water picture. The snow, which forms a vast “frozen reservoir” over California’s 400-mile long Sierra mountain range, provides nearly one-third of the state’s water supply for cities and farms as it slowly melts in the spring and summer months. The melt sends billions of gallons of clean, fresh water flowing down dozens of rivers and streams into reservoirs.

It also is key to the state’s ski industry, which suffered significantly during the 2012-16 drought. That historic dry period caused residential water cutbacks from the Bay Area to San Diego, farm losses across the Central Valley as wells and reservoir levels dropped, and increased wildfire risk for five years.

That drought was broken by the drenching winter of 2016-17. But ever since then, water officials have nervously monitored weather patterns, hopeful that drought conditions don’t re-emerge any time soon.

They also have been wary of climate change, which is expected to slowly shrink the Sierra snowpack in the coming decades as temperatures continue to warm. With massive wildfires and heat waves crippling Australia this week, the issue has gained new visibility.

On Thursday, California officials noted that due to the timing of some major early-season storms, December snow levels in the Sierra finished as the best since 2010. In the years with average to above-average winters since then, the bulk of the snow came later in the winter season, including last year.

“This is the first of our big three months — December, January and February — when we expect half of our annual precipitation,” said Michael Anderson, California’s state climatologist. “The first one has done well. Two to go.”

They cautioned, however, that the totals on Thursday statewide represent just 44% of the historical Sierra snowpack average for April 1, which is typically the end of the winter snow season. And for the next two weeks, a high pressure ridge appears to be building off the West Coast, which could mean dry conditions through the first half of January.

Meanwhile, rainfall totals in parts of the state are mediocre. In the Bay Area, for example, San Francisco has received 6.3 inches of rain, or 71% of its historic average for this date. San Jose is at 62% and Oakland is at 54%. Southern California is faring better, with rainfall in Los Angeles at 168% of normal for early January and San Diego at 212%.

“We still need to see how the rest of the rainy season plays out,” Orrock said. “We might not get another storm the rest of year. There’s no way to know.”

Overall for now, however, despite the weak Bay Area rainfall, California is beginning 2020 with a fairly strong water outlook.

Most of the state’s largest reservoirs are currently near, or above, historical averages for this time of year. That’s due in large part to last year’s wet winter, when the Sierra Nevada snowpack hit 161% of its historic average on April 1.

Shasta Lake, the state’s largest reservoir, near Redding, is currently 73% full, or 117% of normal. Lake Oroville, in Butte County, is currently 59% full, or 96% of normal. New Melones Lake, in the Sierra Foothills of Calaveras and Tuolumne counties, is 83% full, or 143% of its historic average. And San Luis Reservoir, near Los Banos, is 63% full, or 96% of its historical average.

California’s historic drought of 2012-16 may be over. But it’s legacy lives on.