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Influx of Water Fills California's Largest Reservoir

Can Lake Shasta spill? Anything’s possible, but most likely preventive measures will intervene.

California officials prepared for a potential spill by raising the dam gates at Shasta, the state’s largest reservoir, which “continues to swell following heavy rainfall” statewide, according to a story published on January 24, 2024, by Newsweek.

A dam with open spillways, a reservoir, and a snow-capped mountain in the background.

“A deluge of rainfall in the western U.S. has seen Shasta Lake rise by nearly 10 feet in the last week,” the story stated.

Water levels started the upward climb on January 17. Then within the last week water levels reached 1,015.41 feet. As of January 22, water levels measured 1,024.19 feet.

The contrast between Lake Shasta’s abundance of water and Lake Mead’s scarcity is glaring. Lake Mead has been reported at little more than 30% of its capacity, far from the position to spill.

What makes such a significant difference between the two reservoirs? The Upper Sacramento River fills Shasta while the Colorado River serves as the water supply for Mead. Water in the Sacramento River is plentiful, but the Colorado River is hurting because consumption by users exceeded the volume of supplies.

Shasta had suffered from conditions of the historic drought, the same as Mead and other reservoirs throughout California, yet “recovered to a healthy capacity,” as stated in the Newsweek story. Sacramento River is the main river in Northern California and “its drainage basin received much of the rain,” which drenched the state recently, based on the Newsweek report. A total of 1.71 inches of rain doused Downtown Sacramento. Meanwhile neighboring El Dorado County received 1,87 inches of precipitation at the same time. Precipitation patterns play a significant role in the water levels of Lake Shasta, where roughly 90% of the supply comes from rain. “The recent spike in precipitation means that the lake is not far from being completely full,” the Newsweek report noted.

Shasta’s water level reached heights that it hasn’t seen in years. That reservoir formed in the early 1940s when dams were constructed for the river.

The Bureau of Reclamation hasn’t cited concerns about flooding yet.  Don Bader, an area manager for the agency, revealed that there was enough room for an additional 10 feet of water before they must focus on flood measures.

In 2022, the reservoir suffered the same dire fate as as other state reservoirs enduring the extremely severe drought. Recovery started in 2023, partly as the result of a wet winter. The weather helped replenish some other California lakes along with Shasta. Various needs are fulfilled by Shasta, such as irrigation use and hydropower generation. Though water in the lake is plentiful now, experts worry about how the remainder of 2024 will fare.

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