On Sunday, officials ordered the evacuation of nearly 200,000 Northern California residents with assurances that “this is NOT a drill.” Their communities are at risk of being flooded by water from overflowing Lake Oroville, the state’s second largest reservoir.
After years of drought, California has recently been pummeled by rain and snow. That’s caused the lake’s water level to rise so much that water has flowed out not just via the main concrete spillway, but via the emergency earthen spillway, too. In early February, a gaping hole appeared in the main spillway, and it’s since grown. Authorities have determined that the second spillway is also at risk of failing.
The Sierra Club and two other environmental organizations warned about potential problems with the emergency spillway 12 years ago, but federal and state officials rejected concerns and said the spillway met guidelines, the Mercury News reports.
Situations like the one at Oroville Dam could crop up more often in coming years as climate change intensifies California’s cycles of drought and heavy precipitation. The state inspects its dams more than many others (although that’s not saying much), but extreme future storms can be expected to put enormous stress on the state’s essential water infrastructure.