Oroville Dam, the nation’s tallest dam, is releasing water to make room for more in the midst of a still rainy season.
This move is necessary to maintain a safety margin for the massive expected inflows, and is the second time since the dam was rebuilt that its spillway has been used.
The last time this happened was six years ago, when nearly 200,000 people downstream were forced to evacuate their homes and properties due to the overtopping of the entire dam.
The spillway has been opened with minimal floodgate opening, releasing the excess water down the 3,000-foot-long, 180-foot-wide spillway.
In the coming weeks, more rain runoff and snowpack melt is expected, and if too much water comes down too fast, the spillway gate will be opened further to increase flow while still protecting downstream communities.
This requires a complex balance of managing in the new climate reality to keep supplies adequate over multi-year periods, given the extreme swings between both drought and wet conditions.
Despite the risks, the dam provides opportunities for using the lake while it’s full beyond recreation, and serves cities, farms, and 27 million Californians.