Glory be! Lake Berryessa rises to rim of Glory Hole spillway

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Late last October, Lake Berryessa’s water level fell to its lowest point in years. No one expected that, in less than four months, enough rain could fall to bring the lake high enough to get anywhere near the top of the Glory Hole spillway.

And then it did.

Soaking storms in December and January began steadily filling the lake, which hit its low point on Oct. 23 of last year at 855,434 acre-feet, with an elevation of 398.59 feet — 41.41 feet below the spillway, said Roland Sanford, general manager of the Solano County Water Agency. The agency which controls the movement of water from the lake to Putah Creek.

Sanford said even water experts weren’t expecting such a dramatic increase in the lake level with the Glory Hole standing high and dry atop a finger of rock near Monticello Dam.

By last weekend, the Glory Hole was all but hidden, with only the 72-foot-diameter rim visible. Crowds flocked to the Monticello Dam, hoping to catch a glimpse of the lake finally spilling over.

By Sunday, the lake had risen to less than a foot below the rim, and viewers cheered when wakes from passing wakeboard boats spilled some water into the swirling funnel. But the lake still hasn’t spilled on its own.

As of Tuesday, Peter Kilkus, publisher of the Lake Berryessa News, reported that the lake was stable at 439.4 feet, a mere 7.2 inches below the Glory Hole. That puts the lake at 99.9 percent capacity.

Kilkus also noted that the dam had been releasing 700 cubic feet of water per second for the three days prior, up from 45 CFS daily for the previous month, which is why the lake level stopped rising.

At this time last year, Kilkus said the lake level was 401.2 feet — 38.2 feet lower than it was Tuesday. The level rose 35.7 feet since Jan. 1, with a total rainfall of 34 inches recorded there and 7.3 inches added since Feb. 1.

“With this week’s predicted rainfall, the Glory Hole may spill naturally by Saturday,” Kilkus said, adding, “No wakeboard boats to help this time.”

The last time the lake spilled was in 2006, Sanford said.

The visible section of the Glory Hole is 20 feet tall. However, the complete structure is 244 feet from top to bottom, where the spillway empties into Putah Creek. The Glory Hole gets its name from its tube shape, similar to a morning glory flower.

The highest that Lake Berryessa has ever risen above the Glory Hole is 6.70 feet, Sanford said, with a lake elevation of 446.70, recorded on March 2, 1983. At that time, the lake held 1,733,451 acre-feet in storage. The lake is considered “full” at 1.6 million acre-feet, but can rise above that level.

However, it is unlikely that water would ever go over the top of the Monticello Dam, because the dam was designed to let water flow around it and out onto the road rather than go over the top.

According to Sanford, the lake level would have to rise to 455 feet, which would be 15 feet over the Glory Hole rim. Sanford noted that “the Bureau of Reclamation would like to believe that (this scenario) is practically impossible.”

Attention has been focused this week on the Oroville Dam and the damage to its main and emergency spillways, but Sanford said the Monticello and Oroville dams are completely different.

Oroville is an earthen dam, while the 300-foot-tall Monticello Dam is made of concrete set into the rocky hillsides. Sanford said the Monticello Dam was “designed for that (a crisis like Oroville’s) not to happen.”

The Solano Irrigation District’s dam tender told The Winters Express in the early 1990s that the only way the Monticello Dam could fail and put Winters underwater would be a complete failure all at once along the lines of the entire structure.

If that ever were to occur, Winters would be under 40 feet of water in about 15 minutes, with floodwaters reaching all the way to Davis.

A few dam facts

Monticello Dam is located in Napa County, and was constructed from 1953 to 1957. It gets its name from the town of Monticello, which was emptied as part of the process to create Lake Berryessa.

Monticello residents relocated to many areas, including Winters. The remains of the flooded town are sometimes visible when the lake is at very low levels.

The Monticello Dam power plant was completed in 1983, and is managed by the Solano Irrigation District. It supplies power to the Bay Area. Solano Irrigation District supplies the official lake level information to the Express each week.

Water is diverted from the dam approximately six miles downstream of Monticello Dam at the Putah Diversion Dam, providing irrigation to farms along the 33-mile Putah South Canal, which ends at the Terminal Reservoir, which supplies water to the city of Vallejo.

During the construction phase, Lake Berryessa did rise high enough to spill over the top of the dam when it was at about half its finished height, causing damage and delays.

The Glory Hole itself is roped off and when water is spilling in, it is extremely dangerous due to suction, like that of a massive bathtub drain. Swimming is prohibited beyond the ropes.

A Davis resident died in 1997 when she swam toward the Glory Hole and was sucked down the spillway.

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