Environment & Science

Here's what that last storm did for California's water supply

On March 5, 2018 a team of scientists take the third snow survey of the season at Phillips Station in El Dorado County, 90 miles east of Sacramento.
On March 5, 2018 a team of scientists take the third snow survey of the season at Phillips Station in El Dorado County, 90 miles east of Sacramento.
Kelly M. Grow/California Department of Water Resources

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It's been an usually dry winter, and last weekend's atmospheric river was welcome for the snow and rain it brought. But what did it mean for California's water supply?

In truth? Not much.

As of last week, this winter was on track to be one of the warmest and driest on record. So, no one would blame you if you breathed a sigh of relief when that freezing cold storm came through and dumped rain and snow on our parched state. But look at the numbers and you'll see that California's far from recovered.

Before the storm last week, the Sierra Nevada – where Southern California gets a third of its water – had only received 22 percent of their annual average amount of precipitation. The storm raised that number to 39 percent, still far below normal.

"As of right now it's not yet a March miracle," said UCLA climate scientist Daniel Swain. "We doubled it, but that's still not nearly enough. We'd need to get multiple more storms like this to get even close to average in terms of the snowpack this year."

Even though seven feet of snow fell in some areas, burying cars and extending the ski season, what fell was dry and fluffy. The storm didn't carry much water, but it did come down from the Gulf of Alaska, so it was cold. The small amount of precipitation that fell, froze quickly in the mountains. If you melted the snow, you'd find that only about four inches of water actually dropped.

Due to this year's dry winter, the amount of water that localities are being allocated by the state, is low.

The Metropolitan Water District of Southern California, for instance, has requested nearly two million acre feet of water from the state. But since this year's been so dry, the agency is on track to receive only 20 percent of that request, or four hundred thousand acre feet.

"We're barely holding on to a 20 percent statewide project allocation right now," said Demetri Polyzos, an engineer with the MWD.

There's an indication, he said, that our allocation could drop down to 10 percent unless additional storms roll through.

Drought conditions still plague much of the state, including Southern California, where Ventura, Santa Barbara and Los Angeles Counties still suffer from severe drought conditions. So far, Los Angeles has only received about 25 percent of its normal amount of rainfall.

Though, Californian's don't have to worry about their taps running dry, as last year's storms filled our reservoirs to nearly pre-drought levels.

Starting Wednesday, a storm is expected to start moving through Northern California. However, according to  Courtney Obergfell – meteorologist with the National Weather Service in Sacramento – it's only expected to bring about six inches of snow.

California have a true picture of how much water will be available when this rainy season wraps up at the end of March.