Rains raise Northern California reservoir lake levels including at Berryessa

Rain and rising reservoir levels are routine this time of year, but the impact from recent storms is clear, state and local water agencies agree.

A powerful series of atmospheric rivers has delivered a major boost to Northern California’s reservoirs, with several lakes rising rapidly over just a few days as heavy rain and runoff poured into watersheds across the region.

State water officials are watching closely, a massive jump at Lake Shasta, where water levels climbed 16 feet in six days, rising from just over 994 feet on Dec. 19 to 1,010 feet by Dec. 25, according to the California Department of Water Resources. The reservoir is now above the historical average for late December.

Shasta Lake is the state’s largest reservoir by capacity and plays a critical role in flood control, water supply, and hydropower.

Closer to home, local water officials are watching levels rise at Lake Berryessa, which has seen well over 5 inches of rain since storms began Dec. 19.

Lake Berryessa is not part of the state water reservoir system (it is a federal reservoir owned by the Bureau of Reclamation and managed as part of the Solano Project). But the rain doesn’t make those kinds of distinctions, so the local reservoir is seeing just as much of an impact from the recent storms.

Recent December rains in the Lake Berryessa watershed have caused the lake level to rise by more than a foot, reaching approximately 430.94 feet as of Friday morning. The lake reaches capacity at 440 feet.

The ground around the lake is saturated, and that means any future rains will bring plenty of runoff and continued rising lake levels.

How likely is that for the rest of the month and the coming New Year?

While December is bringing active storms, the National Weather Service (NWS) and NOAA’s outlooks for January suggest California’s precipitation chances are mixed, leaning toward drier conditions in Southern California, with near-normal conditions for much of the rest of the state. Weather officials say a weak La Niña favors drier patterns. Some models, though, hint at continued activity in Northern/Central California into early January before any potential shift.

For the most up-to-date information on Lake Berryessa, check the Solano County Water Agency’s monitoring page at scwamonitoring.com/LakeBerryessa/