What Happened to Lake Oroville
Mar 8, 2017 at 10:00am
Emma O'Neill, John Blanchard and Kurtis Alexander, SF Chronicle
A wet winter brought to light problems at the nation’s tallest dam, which controls water delivered across California. As storms raged in early February, dam operators from the state Department of Water Resources released heavy flows down the Feather River, but a crisis began when a crater opened on the main spillway. Days later, water poured over an emergency spillway – essentially a hillside – that had never been used. The erosion of the hillside prompted the evacuation of nearly 200,000 people downstream.
Where is Lake Oroville?
Lake Oroville is located in the Sierra Nevada foothills about 75 miles north of Sacramento in Butte County. The reservoir is fed by mountain runoff from the forks of the Feather River and is the centerpiece of the California State Water Project, which supplies 29 urban and agricultural water agencies. The lake also provides flood control, generates hydroelectic power and helps control salinity in the Sacramento-San Joaquin River Delta.
In drier times
During the drought, Lake Oroville saw its level dip to historic lows. In this photo from Aug. 19, 2014, the reservoir was at 32 percent of capacity. When it is full, the reservoir can hold 3.5 million acre-feet of water. An acre-foot is the amount needed to cover an acre with a foot of water — enough to supply one or two households for a year.
Then came the rains
The unusually wet winter pushed lake levels up through January, and in early February a series of warm storms barreled through. By the end of February, the Oroville area had seen nearly 39 inches of rain, and the mountains that feed runoff to Lake Oroville were hit with similarly heavy snow.