Several hours later the situation appeared less dire, as the damaged spillway remained standing.
The state water resources department said crews using helicopters would drop rocks to fill a huge gouge, and authorities were releasing water to lower the lake’s level after weeks of heavy rains in the drought-plagued state.
By 10 p.m., state and local officials said the immediate danger had passed with water no longer flowing over the eroded spillway. But they cautioned that the situation remained unpredictable.
“Once you have damage to a structure like that it is catastrophic,” acting Water Resources director Bill Croyle told reporters. But he stressed “the integrity of the dam is not impacted” by the damaged spillway.
Asked about the evacuation order, Croyle said:
“It was a tough call to make.” He added: “It was the right call to make.”
Officials said they feared the damaged spillway could unleash a 30-foot wall of water on Oroville, north of the state capital Sacramento.
They said evacuation orders remained in place for some 188,000 people in Oroville, Yuba County, Butte County, Marysville and nearby communities and would be re-evaluated at dawn.
The Yuba County Office of Emergency Services urged evacuees to travel only to the east, south or west. “DO NOT TRAVEL NORTH TOWARD OROVILLE,” the department warned on Twitte