A terrifying hole in a lake in Napa County in California looks like a portal to another world at first glance. Crowds are mesmerized by its bottomless pit style effect as water spirals down in the middle of the lake. This hole is known commonly as the 'Glory Hole from Hell' found in a fenced-off area in Lake Berryessa.

Officially called the "Morning Glory Spillway," the hole is a unique spillway for the lake and Monticello Dam. Rising water levels in the dam that reach above 440 feet create the 75ft-wide swirling vortex in which the water starts to spill down the hole and into Putah Creek.

 75ft 'Glory Hole from Hell' Opens Up Again in A Lake Creating Bathtub Drain Effect: How Does It Work?
(Photo : Wikimedia Commons/Jeremy Brooks)
Glory Hole, Lake Berryessa

Works Like A Drain in A Bathtub

The glory hole has been spotted on the lake's surface several times before in 2019, 2017, and 2006, according to Daily Star. Engineers built the hole in the 1950s to control the flow of water in the lake.

The strange vortex attracted many onlookers who were puzzled by the effect. Some even likened it to water swirling around the bathtub drain after pulling the plug. This drain-like feature is on the southeast side of the dam and reports say that it is capable of swallowing around 1,3000 cubic meters of water per second when the reservoir is overcapacity.

As ABC10 explains, it works like the drain at the side of a sink or a bathtub and happens when water gets too high to prevent overflow. Jim Daniels, District Engineer for Solano Irrigation District, told the local news outlet that the hole is curved to have the least resistance for the water to go down without much turbulence efficiently.

Although it is tranquil on top, Daniels added that it is not that placid down inside the Glory Hole itself. The water drops about 200 feet into a narrowing pipe in which the diameter of the bottom is only 28 feet. Then it takes a 90-degree turn and flows to the other side of Monticello Dam where it spills to Putah Creek and eventually flows into the Yolo Bypass.

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Why Build A Hole Than A Typical Spillway?

Many asked why the lake's spillway was built that way. The simple answer is that there is not enough space to make a big channel and overflow berm,

Engineers at that time thought that the best way to get the water to the other side of the Monticello dam was to dig down and tunnel through the rocks to divert water flow into Putah Creek. That tunnel today serves as the spillway for the glory hole.

Authorities Warn Swimmers in Lake Berryessa of Multiple Drownings

In 2021, ABC10 reported that two people drowned in Lake Berryessa, causing the sheriff's office to release a warning on swimmers. Sgt. Jon Thompson with the Napa County Sheriff' Office said that the water may look safe, but danger lurks below.

"You could be swimming in six feet of water, then all of a sudden its 90 feet and you are still trying to make it to the island," ABC10 quoted Thompson.

The lake is known for its steep underwater drop-offs, but last year's drought caused an inch-a-day drop in water, making beach drop-offs unpredictable.

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Check out more news and information on Dams in Science Times.