Chart Shows Huge Change in California Reservoirs as Atmospheric Rivers Hit

In an aerial view, the Enterprise Bridge passes over a completely full Lake Oroville on June 15, 2023 in Oroville, California. Lake Oroville’s water levels jumped 10 feet in a week’s time after two atmospheric rivers hit the state last week.

Water levels at two California reservoirs leaped by 10 feet after a bout of atmospheric rivers brought a deluge of rain to the state, with another storm on the way.

Last week, two atmospheric rivers hit California. These rivers are defined as a “long, narrow region in the atmosphere—like rivers in the sky—that transport most of the water vapor outside of the tropics,” according to the National Oceanic and Atmospheric Administration. More than a dozen atmospheric rivers battered the state last year, largely eliminating drought but posing problems such as flooding and mudslides.

A chart by the California Department of Water Resources shows water levels at Lake Shasta and Lake Oroville rocketing up by 10 feet in a week’s time because of the rain’s impact. As of Friday, Lake Shasta water levels were at 1,028 feet, a 9 percent change in the lake’s total capacity since last Friday. Lake Oroville’s water levels were at 835 feet, a 4 percent change in the lake’s total capacity in the same time frame.

Another atmospheric river is on the way, and the National Weather Service (NWS) Climate Prediction Center expects there is at least a 70 percent chance for above-average precipitation along California’s coast from January 30 to February 3.

“An impactful atmospheric river event will likely move southward along the West Coast next week, bringing heavy rain and high winds to California and interior regions of the Southwest, along with heavy snow at higher elevations,” the NWS Climate Prediction Center said in a forecast report.

Idamis Del Valle-Shoemaker, a meteorologist at the NWS office in Sacramento, told Newsweek that the rain could begin as early as Tuesday, but the storm was still too far out to predict accurate rainfall totals.

Heavy precipitation could cause localized flooding and landslides, the NWS Climate Prediction Center report warned, “particularly in regions that have recently received heavy rains.”

Depending on its trajectory, the incoming moisture-laden storm could further supplement water levels at both lakes. Improving water levels at Lake Shasta and Lake Oroville is good news after both lakes experienced low water levels during a years-long drought that gripped California. An abnormally wet winter last year alleviated much of the drought and both lakes have drastically recovered, but they still have a way to go before they reach full pool.

A map published alongside the NWS Climate Prediction Center report showed that there is at least somewhat of an increased chance for above-average precipitation next week for the entire western half of the U.S.

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