LAKE BERRYESSA (KPIX) — For the first time in nearly a decade, water from Lake Berryessa is flowing into a unique vertical spillway, a rare sight drawing tourists to see what’s known as the Glory Hole.

Berryessa, a reservoir about two hours north of San Francisco, is formed by the Monticello Dam and features an open bell-mouth spillway, 72 feet wide with a vertical drop more than 200 feet deep. When the lake fills up, excess water pours down the pipe and out the base of the dam.

It looks like a bathtub drain has opened up in the lake.

“I’m wondering how much deeper it’s gotta be before it turns into a whirlpool,” a man watching the strange sight remarked.

The crowd waiting to see the Glory Hole in action kept getting larger on Friday but the nearby Canyon Creek camping resort is moving people out because outflow from the spillway is flooding some of the lower campsites.

  1. It is one of a rare type of spillways for dams. It is called a ‘Syphun Spillway.