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California enjoying increasingly rare back-to-back wet winters

Winter rainfall is near average yet still uncommon
Winter rainfall is near average yet still uncommon 04:12

Northern California has seen a lot of rain in recent weeks, but this winter is also delivering something the state hasn't seen much of this century.

The winter of 2022-2023 brought that long parade of strong storms that took turns battering parts of Northern California. And it all added up. Northern California saw above average rainfall that was enough to end the drought and fill most of the state's reservoirs.

Oroville spillway
Oroville spillway KPIX

So how is this year looking? It's looking perfectly average. Despite all of the recent storms, the northern part of the state is currently right on track for average rainfall in Northern California. And believe it or not, average is increasingly unusual.

"Shasta and Oroville are well above their historical average. but they're not full," explained Jeffrey Mount with the PPIC Water Policy Center. "They can't be full. You have to leave some space to manage floods."

Mount is watching the reserves stack up across California. He says the winter of 2023-2024 is quickly becoming a remarkable one, if one takes the wide-angle view.

"Here I've just plotted precipitation back to 1950, and this is through 2022," he said, pointing to an array of years. "And one of the really striking things about the 21st century, post 2000, is the dry years. A lot of dry years."

The drought that stretched from 2012 to 2016 was considered the worst on record. That dry stretch ended with the wettest year on record in Northern California in 2017. And almost just as quickly, the state descended right back into more years of drought.

"The so-called average year like we're having now is becoming rarer and rarer. And this is a climate change signature," Mount said of the trend. "Our wet years are becoming wetter, and our dry years are becoming dryer. That's the signature that's really starting to show up."

And this average winter northern California is enjoying gets even more notable when considering how rare it is becoming to have a wet year, like last year, followed by anything other than a dry one.

"We're almost a quarter done with the 21st century, and we've only had two pairs of years where we've had wet back-to-back years," Mount explained. "This one, and back in 2004-2005."

So California, a state built on the whims of variable weather, is only seeing more of it, as extremes become the norm, and average becomes increasingly uncommon.

"But what's happening is that the variability seems to be increasing," Mount said. "The drys are getting dryer, Te wets wetter. That's our huge challenge into the future."

Southern California has had a really big year of rainfall, but most of the state's precipitation and storage is up north, even if 75% of the people who use that water live down south. 

Two strong water years back-to-back is great news for the entire state, and there's still some time left on the clock for this winter to deliver more rain.

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