California’s largest reservoir surges 30 feet after recent storms

Lake Shasta, California’s largest reservoir, has risen more than 100 feet in the past two weeks as a series of winter storms hit the state, according to state data.

Heavy holiday runoff and Lake Shasta rising just 10 feet between Friday and Monday pushed water levels in the sprawling Northern California reservoir to about 80% of capacity; this is well above the level typically held this early in the rainy season. And the second round is still coming, albeit slower.

While winter is still young and California’s water picture won’t be clear for months, the recent replenishment of Lake Shasta and other major reservoirs is welcome news for the state’s cities and farms, which depend on the water that fills these giant storage facilities between fall and spring.

“Overall, reservoirs are performing above average, which is a good thing,” state climatologist Michael Anderson of the California Department of Water Resources said in a report to the State Water Resources Control Board on Tuesday.

Before the holidays, water managers were nervous after the state’s peak rainy season, which runs from December to March, got off to a mostly dry start. But an extremely wet situation that began just before Christmas brought more than a foot of rain and more than a few feet of snow to some parts of California in a two-week period.

“There were over 100 hours of atmospheric river conditions in the state around the Christmas holiday,” Anderson said.

As a result, water storage at Shasta Lake increased to 132% of historical average as of Monday. Storage at Lake Oroville, the state’s second-largest reservoir, increased to 135% of average. Storage at Trinity Lake, the state’s third-largest reservoir, reached 137% of average.

Meanwhile, San Francisco’s primary storage facility, the Hetch Hetchy Reservoir in Yosemite, was holding 130% of the water it normally held on this date.

Many reservoirs release water to provide adequate space for persistent rainfall and ongoing runoff. The waters of Lake Shasta were approximately 35 feet below the edge of the reservoir.

“We are on the side where inflows are declining with these latest systems,” said Levi Johnson, operations manager for the federal Bureau of Reclamation, which manages Shasta Lake. “This is going to be a dynamic operation in terms of what kind of releases we have.”

The storms seem to be largely over. The National Weather Service is predicting dry conditions for at least the next two weeks.

As California’s water situation remains strong, water managers will be watching to see how long until the next rain and snow arrives and whether that’s enough to maintain strong reservoir storage.

Another factor water managers are monitoring is snowfall in the northernmost part of the state. California’s total snowpack was 90% of average for that date, while in the northern Sierra and southern Cascades it was only 67%.

Snow is especially important in Northern California, where the state’s largest reservoirs are located, because it melts after the rainy season ends and provides a water source for the reservoirs.

“We had more rain than snow,” Anderson said.

This article was first published at: California’s largest reservoir rose 100 feet after recent storms.