Statewide snowpack in the Sierra Nevada — the source of nearly a third of California’s water supply — is at its highest level since 1995, fueling hope that the drought is near an end, but also raising concerns that a couple of warm spring storms could melt it too early and trigger large floods.
Since Toy Story packed theaters, Steve Young led the 49ers to their fifth Super Bowl win, and gas cost $1.28 a gallon, California’s most famous mountain range hasn’t had this much snow at the end of January.
“It’s absolutely massive,” said Kevin “Coop” Cooper, a ski resort consultant who lives near South Lake Tahoe. “I’ve spent so much time with my snow shovel that I gave it its name. My wife thought I was having an affair.”
Snow cover was 205% of its historical average for this time of year on Wednesday, the morning of the high-profile snow survey Feb. 1 that state officials planned to conduct with television cameras near Highway 50 at the Sierra-at-Tahoe ski area. The last time there was more snow 28 years ago, on February 1, 1995, it was 207% of normal.
According to an analysis of historical data by Bay Area News Group, the huge bounty is the fourth largest statewide since 1950, when consistent statewide records began. Only 1952 (267% of average) and 1969 (230%) and 1995 (208%) had larger amounts on February 1st.
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In some places, like Highland Meadow in Alpine County, snow cover is the greatest on record.
Around Lake Tahoe, stop signs and fire hydrants have been buried in snow. Ski resorts that struggled with drought, wildfires and COVID for three years see a successful year. Tuesday’s snow base at Palisades was 11 feet deep. At Kirkwood it was 12 feet. And at Mammoth Mountain, south of Yosemite National Park, it was almost 20 feet deep.
“We had to dig a lot,” Cooper said. “I’m looking at a neighbor’s house right now. He has to shovel on his roof. Gutters can fill up, freeze and fall off the house. Or if you have a flat roof, it can collapse under the weight of the snow.”
The winter windfall came in a series of nine atmospheric river storms that began around Christmas and lasted three weeks. Since then, temperatures in the mountains have been cool and preserve much of it.
Snow is vital to California’s water supply. Many winters, storms blanket the Sierra, a 400-mile rocky expanse hailed by naturalist John Muir as “The Range of Light” that includes the highest peak in the lower 48 states, Mount Whitney, along with the magnificent granite walls of Yosemite Valley and the lofty shores of Lake Tahoe.
It melts in late spring and early summer. Billions of gallons spill over more than a dozen Sierra rivers like the Merced, Tuolumne, American, and Feather. The water is collected in large reservoirs. It also recharges underground aquifers, providing food and habitat for fish and wildlife.
But in dry years, when there are fewer storms, there is far less water available for cities, farms and the environment.
The January storms caused severe flooding in the Sacramento, Santa Cruz, Merced and Santa Barbara areas, killing at least 22 people and causing power outages, mudslides and other damage.
The water also began to fill reservoirs across the state. The largest, 35-mile Shasta near Redding was 56% full Tuesday, or 87% of its historical average for the date. The second largest, Oroville, in Butte County, was 65% full, or 112% of its historical average.
Many large reservoirs are sure to rise higher as the snow melts in the coming months.
“The storms could switch off,” said Jay Lund, a professor of civil and environmental engineering at UC Davis. “This is the worst case. But even in the worst case we still have a good snow cover. Most of it is in the bank and will appear as streamflow.”
State water authorities are excited about the start of this winter. They also carefully eye all the snow.
“The snowpack is great,” said David Rizzardo, chief engineer with the State Department of Water Resources. “But it also offers a very unique challenge.”
Simply put, the drought will end if rain and snow continue to fill reservoirs. But if California gets big, warm, soggy storms parking over the Sierra, much of the snowpack could suddenly melt and wreak havoc.
That’s what happened in 1997. Several warm Pineapple Express storms drenched the Sierra around New Year’s Day. Yosemite Valley experienced its worst flooding in a century. Entire campsites washed away. Half of Yosemite Lodge was destroyed. On the other side of the Central Valley, large reservoirs filled to the brim and released water uncontrollably. Levees collapsed, causing major flooding in Marysville, Yuba City, and other communities. When it was over, 48 of California’s 58 counties were designated disaster areas, and damage totaled $1.8 billion.
Hoping to reduce the likelihood of a similar event, dam operators have increased water discharge from some reservoirs, such as Folsom northeast of Sacramento and Millerton near Fresno, in recent weeks to make more room.
It’s a delicate balancing act. Farms, cities and politicians want to save as much water as possible. The public sometimes forgets that the dams were built not only to store water but also to reduce flooding, experts say.
“You want to be able to reduce currents downstream to allow time for evacuations or levee repairs,” Lund said. “You really don’t want to lose control when you run out of storage. We don’t want to kill anyone downriver. That is the bottom line.”
If the rest of spring goes well, moderate storms interspersed with dry spells will roll in, allowing the reservoirs to gradually fill up further just as summer begins and the risk of flooding ends.
“In a perfect year,” Lund said, “you refill the reservoirs right at the end of May.”