Lake Berryessa's ‘Glory Hole’ sees a scenario that may 'never be duplicated'

Lake Berryessa's spillway, famously known as the “Glory Hole,” has been on the brink of activation for more than two weeks, hanging a few inches away from a full spill for what's likely the longest time on record. It's a scenario that has baffled many, including the engineer who monitors water levels in the California reservoir, two hours north of San Francisco.

"Since April 1, it's been within an inch of spilling," said Jay Cuetara, supervising water resources engineer for the Solano County Water Agency. "The lake may come up and get to be an inch away and then it will slowly back off because the rain stopped. It's just a crazy year."

Cuetara has been with the water agency, which manages the dam at Lake Berryessa, for 18 years. To his knowledge, this year marks the longest period of time the lake has ever been so close to the edge without officially spilling. "I can guarantee that it will never be duplicated," he said. "This is really a once-in-a-lifetime year."

Spillways allow for the controlled release of water from reservoirs, in many cases, reducing the risk of catastrophic floods. Lake Berryessa's spillway has an unusual design: When the surface of the reservoir tops 439.96 feet, water pours into the 72-foot-wide mouth of a massive pipe. The funnel-shaped tube carries water out below the lake's Monticello Dam and releases the water into Putah Creek, Cuetara said.

The Glory Hole only spills in years marked by especially wet winters. That certainly applies to this past season. Between Oct. 1 and today, total precipitation — which includes both rain and snowfall — has been above average, according to the California Department of Water Resources. In recent history, Lake Berryessa overtopped the spillway in 2019, 2017 and 2006, according to Cuetara.

When that happens, the Glory Hole becomes a popular attraction.

Even this year's activity has attracted lookie-loos. With the water level within a foot or less of the top of the pipe, wind and boat wake have been sending water "dribbling" into the spillway, he said.

"When I drive by every day people are flocking there to see it," said Crystal VanWart, the administrative manager at Pleasure Cove Marina on Lake Berryessa, told SFGATE on Thursday. "It's a really big thing."

Such activity has led a few social media accounts to incorrectly claim that the spillway is currently active, Cuetara said. On Monday, the U.S. Bureau of Reclamation shared a social media post that read, "She's full!" with a video showing what looks like water flowing into the spillway.

This year, the lake has been in the 439-foot range since mid-March. It reached its highest point at 439.95 feet on April 8 for one hour, spilling a little bit of water.

"The water has gotten so close to the edge of the spill that it's dribbling over, but it's not enough to physically be able to measure," Cuetara said. "So officially, it's not considered a spill."

The Bureau of Reclamation completed construction of the spillway and the Monticello Dam, which impounded Putah Creek to form Lake Berryessa, in 1957. Holding up to 1.6 million acre-feet when it's full, the lake supplies water to households, businesses and farmers in Solano County, while the dam power plant creates hydroelectric power. Water also gets released to support fish habitat in Putah Creek, Cuetara said. The lake is a popular spot for recreation and boating but undoubtedly its most famous feature is its spillway, originally named the Morning Glory but later nicknamed the Glory Hole.

"It's been called the Glory Hole since 1960," Cuetara said.

As for whether the lake's big attraction could still put on a show this year, Cuetara said it's unlikely.

"Each day that it goes without a big storm in the forecast, there becomes less and less of a chance because the ground dries out," he said. In addition, warming temperatures mean more evaporation, and water management officials will soon begin releasing water from the reservoir to farms in the region for the growing season.

Still, there's some chance. "I would say if we got one pretty good storm that really hit the watershed, it would probably be enough to push us over the edge," Cuetara said.