Back-to-back atmospheric rivers have dumped buckets of rain across Northern California, filling its rivers to the brim and beyond. The Russian River spilled over its banks in Sonoma County, and in the far reaches of the state, Lake Shasta, a key marker of the state’s overall water levels, has nearly filled up.

And just east of Napa Valley, a rare not-fully-natural phenomenon was observed for the first time since 2019: Water began gushing, furiously, through a spillway in Lake Berryessa.

The eye-catching event has happened only three other times in the past 20 years, and it has drawn curiosity seekers to the man-made reservoir, 70 miles northeast of San Francisco.

“People were taking pictures and videos and just standing in awe,” said Peter Kilkus, the editor of the Lake Berryessa News, who was there Wednesday morning with about two dozen other people.

The 72-foot-wide spillway, called a morning glory because its shape mimics the flower, is a unique funnel-shaped cement pipe that sits within the reservoir. (Locals call it the glory hole.)

The mechanism is a type of drainage system with water pouring down the pipe and into Putah Creek on the other side of Monticello Dam. The spillway is among a few with that shape in the country; there’s also a smaller one at Whiskeytown National Recreation Area near Shasta, Calif., and it spilled over this week, too.