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Northern California's dry January only put a minor dent in region's water supply

Despite lack of rain in January, Northern California water supply remains healthy
Despite lack of rain in January, Northern California water supply remains healthy 06:09

The incoming storms follow what has been an exceptionally dry January for the Bay Area, with the lack of rain having an impact on the region's water supply.

Healdsburg residents Tom and Molly Nicol visited Lake Sonoma to see where its water levels stood before they rise again with the rain from this weekend's atmospheric river.  

"Yeah, when the water is up to the bottom of those trees over there, you know it's full," laughed Tom. "And you can see that it's dropped a little bit from the last storm we got in December. So it's down a little, but it's full."

There is still room in the lake, with a good chunk of winter yet to come.

"That's the thing. You need more storms," explained Jeffrey Mount with the PPIC Water Policy Center. "We need somewhere in the order of five to seven big storms. That makes up the bulk of our precipitation. Just the difference of two storms can be the difference between an average year and a wet year."

Mount cautions that this winter's full story is yet to be written.

"We can tell what kind of year it's gonna be by the end of February," he said of California's water year. "That's it. And then we kinda know what it's gonna be like."

So where do things currently stand? After significant rains in November and December, the dry January has landed Northern California right back at an average winter. But looking at reservoirs like Lake Sonoma, the situation is better than average. 

For that, Californians can thank the current streak of wet winters, which could turn into something very out of the ordinary.

"Shasta and Oroville are well above their historical averages," Mount said of the state's largest reservoirs. "So we're about average, and our reservoirs are in really good shape right now. That's the one thing. Even in the dry parts of the state."

It is the continued payoff of the good year, and then an average year. Throw in another average year and -- as far as recent decades -- that's a pretty decent three-year stretch.

"Yeah, and in two ways," Mount explained. "One is we don't get back-to-back wet years. It just doesn't happen in the system. We usually have intervening dry years. 2017 was very wet. 2018 was dry, 2019 was wet. So yeah, '23 and '24 were really unusual. And if we come up with an average year on top of that, that is unprecedented in the 21st-century, is the best way to describe it. We haven't seen that."

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