How California Reservoir Water Levels Changed After Atmospheric Rivers

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One reservoir in northern California rose by 5 feet after two atmospheric rivers supplemented the water levels.

An atmospheric river began across much of the Pacific Northwest, including Oregon and Northern California, on Friday. An atmospheric river is 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. Last year, more than a dozen atmospheric rivers battered California, largely eliminating the state’s drought but posing problems such as flooding and mudslides.

The ongoing storm is anticipated to last through the first part of this week, and Lake Shasta in Shasta County has already benefitted from the onslaught of rain.

The Pit River Bridge stretches over a drying section of Lake Shasta in Lakehead, California on October 16, 2022. Lake Shasta has risen 5 feet after an atmospheric river brought rain to the area over the weekend.
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On Friday morning, Lake Shasta’s water levels were at 1,015 feet. They had risen 5 feet to 1,020 feet by Monday morning.

National Weather Service (NWS) meteorologist Kate Forrest told Newsweek that up to 8.5 inches of rain has fallen in Shasta County since the storm began on Friday. The region is currently experiencing the second of two atmospheric rivers, the first of which passed through the area on Friday and Saturday. The second precipitation-laden storm began on Sunday.

“Precipitation should start to wind down later today with a few lingering shows continuing into Tuesday,” Forrest said.

Lake Shasta, which had concerningly low levels in 2022, has started to rise since the start of the year after falling slightly at the end of last year. The atmospheric rivers last winter aided in the lake’s recovery, in which levels rose by 135 feet from January to May 2023.

In June, before-and-after satellite images revealed the lake’s drastic recovery when water levels reached nearly 100 percent capacity after being in a dire state since 2019 because of a prolonged drought.

The weekend increase to the lake’s water levels contributed 1 percent to the lake’s total capacity, bringing Lake Shasta to 71 percent capacity, according to a report by the California Department of Water Resources. Although further improvement is still needed before the lake reaches full pool, its levels are still 113 percent of the historical average.

More rain is on the way, and the NWS issued a flood watch for Shasta County early Monday morning. The forecast warned that isolated thunderstorms with heavy rain would occur Monday afternoon. The flood watch will remain in place through late Monday night.

A weaker storm system will arrive Wednesday, but Forrest said dry weather will return by the end of the week. She added that the atmospheric rivers were not abnormal weather patterns for the region.