It’s Official: California Sierra Snowpack Ties All-Time Record


California water officials gathered at Echo Summit south of Lake Tahoe this morning for a high-profile snowpack reading, which confirmed what an army of snow-sensors scattered across the Sierra already show: the statewide snowpack is tied with 1952 as the biggest haul since official records began in 1950.

On Monday, the statewide snowpack reached an astonishing 237% of normal compared to historical data for this date. The record-tying snowpack is a stunning turnaround from a year ago, when the official April snowpack measure was one of the lowest readings ever, at just 35% of normal.

Technically Monday’s snowpack reading came two days after April 1 — the typical date against which snowpack readings are compared. On April 1, the statewide snowpack measure was at 233% of normal, which was a few percentage points shy of the 1952 record.

But here’s the thing about all these snowpack readings; California has way more stations collecting snowpack data now than it did in 1952. And the data they collect with modern technology is far more accurate.

Also, what’s considered ‘normal’ for an April 1 snowpack reading has changed over time. “Normal” April 1 snowpack in 1952 was calculated based on data from 1946 to 1995. But “normal” nowadays is calculated based on data from 1991 to 2020. The California Department of Water Resources, which compiles all the snowpack data, has used five different definitions of ‘normal’ since 1950, making it difficult to easily compare years. Why, you may ask, do they keep changing the definition of what’s considered normal come April 1? The shifting average is designed “to keep pace with climate change,” according to Sean de Guzman, manager of the California Department of Water Resources’ monthly snow surveys.

Regardless of how you measure it, though, this year’s massive bounty is great news for the drought, which has ended in most of the Golden State. Around a third of California’s water supply comes from melting snowpack.

But many experts are expressing growing concern that warm temperatures in the Sierra this spring could trigger cataclysmic flooding. They are particularly worried about snowmelt-fueled flooding in the Southern Sierra, where the snowpack was at a record-breaking 306% of normal on Monday.

“Once you get up above some level, you are mostly concerned with how fast it melts rather than how big is the snowpack,” said Jay Lund, professor of Civil and Environmental Engineering at UC Davis. “If we get a real warm spell that comes through and melts it all real fast, you’ll see much more flooding potential.”


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