Look at California’s Record Snow Pack ~ NYT

Photographs and Video by Erin Schaff

April 4, 2023

Up and down the high slopes of the Sierra Nevada, the barrage of heavy storms that deluged California this winter also left behind a giant frozen reservoir, one whose thawing will shape the next phase of what has already been a remarkably wet year for the drought-weary state.

Snow, huge imposing walls of it, has blanketed the Sierra’s majestic peaks and mountainsides, in quantities that parts of the area have never previously recorded.

It has fallen in totals that defy easy imagining: 654 inches at Mount Rose near Lake Tahoe, 702 inches at Mammoth Mountain. When converted into an equivalent depth of water, it is nearly double the historical average for this point in the year across the Sierra’s northern reaches, where the runoff feeds several major reservoirs. In the southern Sierra, it is around triple the average.

Statewide, this season’s snowpack is on course to be either the largest or the second largest since modern records began in 1950, Sean de Guzman, the manager of the California Department of Water Resources’ Snow Surveys and Water Supply Forecasting Unit, said on Monday.

The sheer immensity of the snowpack has sparked delight among skiers and a more complex brew of emotions among farmers and water managers, who are ready to embrace the watery bounty but are also girding for the possibility of more catastrophic flooding this spring.

The recent storms have led Gov. Gavin Newsom to lift some drought restrictions, but parts of California are still struggling to meet their water needs, particularly rural communities in the Central Valley that rely on groundwater wells. As the snow melts in the coming months, the valley might have to deal simultaneously with “very, very significant flooding” and with drought-related water supply challenges, said Karla Nemeth, director of the Department of Water Resources.

Figuring out how much snow piles up in the Sierra each winter is critical. For a long time, officials and forecasters did this primarily by sticking long metal tubes into the snow and weighing the icy core caught inside. Today, these low-tech measurements still serve as an important baseline, but sensors mounted on low-flying airplanes provide a much more comprehensive picture.

On Friday, a twin turboprop from the National Oceanic and Atmospheric Administration flew a five-hour course over the Sierra, using specialized instruments to gauge the amount of water in the deep white carpets below. Within minutes of being collected, the data was sent out for use in forecasts of river levels and flood hazards.

A woman wearing aviator sunglasses and a headset looks out the window of an in-flight airplane. The view shows snow-covered mountains. — Carrie Olheiser, a snow hydrologist on the NOAA snow-survey mission.

A photo taken from an airplane shows a cluster of trees at the base of an incline blanketed in snow. — The flight uses specialized instruments to collect data on the snowpack, which is then sent out within minutes for use in forecasts of river levels and flood hazards.

A close-up shot shows someone writing in a notebook that is illuminated by light from an airplane window. — Ms. Olheiser logged her observations in a notebook.

“There hasn’t been a lot of snow to talk about in the Sierra for the last few years,” said Carrie Olheiser, a snow hydrologist with the research organization RTI International who supports NOAA’s snow-survey missions. The comparison with this year’s levels, she said, is “night and day.”

For NOAA’s pilots, who must traverse craggy backcountry terrain while hugging the ground at 500 feet, a snow survey like Friday’s involves a good amount of adventurous flying. As they wound through the narrow valleys, the plane’s navigation system emitted a noisy flow of alerts offering to help them land — or avoid crashing into the mountain ahead.

The big question for California now is how quickly all this snow will melt and rush into, and possibly overwhelm, the state’s rivers and reservoirs — something that is becoming trickier to predict as the planet warms.

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