California's Largest Reservoir Sees Water Levels Jump Ahead of Major Storm

A California reservoir has added 10 percent to its total capacity in two weeks after a slew of atmospheric rivers saturated the state, and more rain is on the way.

Various winter weather warnings were in place for California on Thursday morning as the first of two atmospheric rivers brought rain and wind to the state. A forecast map shared by the National Weather Service (NWS) showed that rain will fall across the entire state, with the highest amounts forecast for northern California. As of Thursday morning, Redding, near Lake Shasta, had received 1.19 inches of rain, although the heaviest part of the storm has passed, NWS meteorologist Chris Hintz told Newsweek. The area could pick up another half-inch throughout the day.

Atmospheric 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 creating severe problems such as flooding and mudslides.

Lake Shasta water levels have jumped significantly in the last two weeks. As of Thursday morning, the lake's water levels were at 1,033 feet, 18 feet higher than the levels were at in the middle of January. The rise in water levels equates to 10 percent of the lake's total capacity. Lake Shasta is California's biggest reservoir.

According to a chart by the California Department of Water Resources, Lake Shasta water levels are at 80 percent capacity, 122 percent of the historical average.

The second atmospheric river beginning on Sunday could bring an additional 2.5 inches of rain to the area, which could further supplement the lake's levels.

The lake experienced low water levels in 2022 after a years-long drought gripped California. An abnormally wet winter last year alleviated much of the drought and the lake has drastically recovered.

Despite the lake's recovery, officials haven't needed to open the dam's spillway since 2017.

Now, at just over 1,033 feet, Lake Shasta's water levels are 46 feet higher than this time last year. United States Bureau of Reclamation (USBR) spokesperson Mary Lee Garrison-Knecht told Newsweek that as of Tuesday, the USBR had increased releases "at Shasta and its regulating reservoir...for storage management."

Atmospheric rivers have contributed to California's drought recovery, but they can also pose risks with heavy flooding. Meteorologists are more concerned about the second atmospheric river that is forecast to hit over the weekend.

"The next one looks to be in more of an intensifying phase as it gets closer to the coast," NWS meteorologist Marc Chenard previously told Newsweek. "It is slower moving, so the duration will be longer."

There is uncertainty with the second storm's forecast, as it is still days away.

Although the brunt of the first storm is expected to hit the Pacific Northwest, the NWS forecast shows that 2 to 4 inches of rain could fall along the southern coast of California as well. Rainfall will begin in Santa Barbara, Los Angeles and San Diego on Thursday.

After the storm lashes the West Coast, it will move throughout inland states.