The Oroville Dam Emergency: What’s the Deal?

Water cascading down the Oroville Dam emergency spillway (photo by William Croyle).

By Tommy Hough

The Oroville Dam emergency in Butte County is making a lot of headlines, and for good reason. It’s a scary situation, and a collapse of the dam would have consequences for the entire state.

Here’s the deal: we’re having an unusually heavy winter with lots of rain, but in the foothills of the Sierra Nevada in Gold Country, it’s been an absolute deluge after five years of drought. While this means the state is going to have water for homes and crops this year, Lake Oroville, the massive man-made lake behind Oroville Dam that serves as the starting point for California’s State Water Project, is bursting at the seams.

At 770 feet, Oroville Dam is the highest dam in the U.S. (45 feet higher than Hoover Dam), and for the first time since it went on-line in 1968 operators began releasing water into the dam’s emergency spillway. That rush of wild-flowing water – which looked like Niagara Falls on TV – rapidly began to erode the dam’s earthen slope. While the emergency spillway was supposed to have been able to handle high flows from the dam, it had never been used before – and it carved dangerously deep gulleys into the structure that could undermine the dam.

As a result, at least 180,000 Californians from Gold Country counties like Butte, Sutter and Yuba downstream from the dam and the Feather River were evacuated, and hotels and shelters as far away as Sacramento became packed. The good news is the mandatory evacuation orders have since been lifted.

However scary this scenario is, some agree this may be a worthwhile exercise for the state, which may receive less-than-speedy, or capable, FEMA response over the next few years. The Golden State already a saw a slow response to an earlier gubernatorial request for a federal disaster declaration, though that has since come through.

But it’s not just a dam collapse that worries state leaders. Operated by the U.S. Bureau of Reclamation, the Central Valley Project enables large-scale farming in the state, irrigates more than three million acres of farms and provides drinking water for more than one million Californians. A system of 22 reservoirs were built from 1937 to 1960 to distribute the water, extending 400 miles from the Cascade Mountains near Redding to the Tehachapi Mountains near Bakersfield.

The good news is the rest of the state chipped in and came to the rescue of the Gold Country evacuees, including at least 16 volunteers from San Diego who went north to feed and care for their fellow Californians. But with more rain in the forecast this weekend and emergency work continuing, it remains to be seen what will become of the nation’s tallest dam this winter.

You can get more information about volunteering or helping out the Oroville area in this Sacramento Bee article.

The San Luis Reservoir in Merced County in drier days in May 2015. Note the low water level.