Lake Berryessa’s Giant “Glory Hole” Finally Sees Some Action After 5-Year Dry Spell

They say if you stare into the abyss, the abyss stares back at you. Visitors to Napa County, California, can put that theory to the test because – good news! – Lake Berryessa’s glory hole is back in action.

That’s the Morning Glory Spillway, to be exact: a massive, swirling drain at Monticello Dam designed to prevent flooding when Lake Berryessa’s water levels exceed 134 meters (440 feet). When that happens, the overflow spills into the drain, creating a sloshing vortex that looks very cool when viewed from above.

So, why call it a glory hole?

“My guess is because there’s a big hole and so people have chosen to utilize other terms,” Melissa Vignau told ABC10, “but the official term is the Morning Glory Spillway.”

Vignau is a supervisor for the Solano Project, a federally funded program with the Bureau of Reclamation that supplies water for human use via Monticello Dam. Dams need emergency spillways to handle excess water, and in this case, the glory hole functions like an overflow drain in a kitchen sink, just on a massive scale.

According to the LA Times, the glory hole has only been used 25 times in its 70-year history. It had been sitting dry and unused for years, but at the start of 2025, a slew of atmospheric rivers brought a large amount of rainfall to the region.

At last, the glory hole was back in action.

As Lake Berryessa News reports, the hole first spilled on February 4 and saw the most action on – of all days – Valentine’s Day, when water levels rose to 135.02 meters (442.97 feet). We’ve enjoyed 46 glory hole days this year, and as of March 22, the levels had once again risen to 134.4 meters (441 feet) following a lot of rain in the last few days.

As you can see from the above drone footage, flow into the glory hole is rather peaceful, but it’s a very different story deep inside the glory hole. The water plummets 61 meters (200 feet) before rushing out into the Putah Creek below. Not a day you want to be caught up there without a paddle.

Lake Berryessa is nestled within the crack of a canyon, which is why it needed its own glory hole. Most dams use flat, open terrain to control overflow with wide spillways or controlled gates that guide excess water, but space is limited when you’re wedged in a canyon. Instead, engineers created a drain that could utilize a tunnel they’d already built for rerouting the Putah Creek during the dam’s construction.

Ingenious human engineering meets our species’ penchant for giving ridiculous names to serious things? Now that’s my kind of science story.

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