How Two California Reservoir Water Levels Changed After Atmospheric River

California’s two biggest reservoirs have risen by several feet since Sunday after yet another atmospheric river lashed the state with rain.

California has faced a slew of atmospheric rivers this winter. Last year, more than a dozen of them helped alleviate the state’s severe drought situation and replenished many of the state’s reservoirs, but the storms also caused devastating floods and landslides.

Another moisture-laden storm arrived in the Golden State on Sunday and brought heavy rain to the northern half of the state first before working its way south on Monday. Since the storm’s arrival, Lake Shasta and Lake Oroville in Northern California have risen by nearly 4 feet and 3 feet, respectively.

Atmospheric rivers are 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.

Both reservoirs have significantly improved after reaching concerningly low levels in the summer of 2022. The lakes began to recover last winter thanks to the atmospheric rivers that brought torrential rain to the state. Images of their recovery have abounded on social media.

Water levels at both lakes have continued to improve this winter, and the California Department of Water Resources had to open the gates at Oroville Dam earlier this month to mitigate a downstream flood risk. Despite billions of gallons of water rushing downstream, the lake’s levels have continued to rise.

Lake Shasta is more than 50 feet higher than it was during this time last year, and Lake Oroville is 30 feet higher than its levels in late February of 2023.

The ongoing atmospheric river has added to the water levels at both lakes. National Weather Service (NWS) meteorologist Dakari Anderson told Newsweek that since Sunday morning, Shasta Dam has received 4.96 inches of rain and Oroville, California, has received 2.16 inches of rain.

As of Tuesday morning, a flood watch was in place for both Redding, California—home to Lake Shasta—and the city of Oroville because of continued rain from the storm.

“Excessive runoff may result in flooding of rivers, creeks, streams, and other low-lying and flood-prone locations,” an NWS advisory said. “Creeks and streams may rise out of their banks. Flooding may occur in poor drainage and urban areas. Low-water crossings may be flooded. Storm drains and ditches may become clogged with debris.”

Anderson told Newsweek that the flood watch will remain in place through Tuesday night. Rain will taper off by Wednesday morning.