An unusual — and hypnotic — event is taking place at a lake in Northern California.
The Morning Glory spillway — dubbed by locals as the “Glory Hole spillway” — at Lake Berryessa in Napa, Calif., is active for the first time since 2019, Jennifer Onufer of the Bureau of Reclamation, which manages water resources in the Western U.S., said in an email .
This means that what looks like vortex 72 ft. in diameter has appeared on the surface of the water — one that Onufer noted may be visible for about another three weeks “depending on the weather.”
While the phenomenon may seem eerie to some onlookers, it is actually a sign that the water-release mechanism of the nearby Monticello Dam is working effectively.
Morning Glory spillway at Lake Berryessa on March 14, 2025.
JOSH EDELSON/AFP via Getty
When water rises above a certain level the dam must release the excess volume through what’s known as a “spillway” in order to prevent structural damage. While most dams rely on spillways shaped like chutes or shafts to drain the overage, the dam at Lake Berryessa uses a funnel-like spillway due to lack of space, per local news outlet The Press Democrat.
Morning Glory spillway in Napa, Calif. on March 14, 2025.
The result? The appearance of a massive and mesmerizing circular hole.
Brontë Wittpenn/San Francisco Chronicle via Getty
Once the water drops down the opening, it travels down a massive drain and is released into the outflow pipe into Putah Creek, per the Press Democrat.
While speaking to CBS News, local historian and scientist Peter Kilkus calls the design of the Glory Hole spillway “very rare,” adding, “There are only two in California, and there are a couple others in Europe.”
“Some people say, ‘Oh, that’s really beautiful.’ Some people say, ‘That’s frightening,’ ” he added.
When water levels are low, the spillway juts out over the dam’s water line, but is activated when the water level exceeds about 440 feet above sea level, per The Los Angeles Times.
While speaking to The Times, Chris Lee, the general manager for the Solano County Water Agency, noted that the Glory Hole spillway was initially activated on Feb. 4. KTVU 2 later reported that water levels peaked on Feb. 14 at 443 ft.
The increased water levels are due to the recent wet winter in Northern California, per the outlet.
While the spillway will remain active for another several weeks, the Bureau of Reclamation is currently warning motorists that there will likely be increased traffic and congestion along State Route 128 due to current public interest in the site. They also ask that any visitors viewing the spillway by boat be mindful of “our new invasive mussel prevention protocol,” per their email PEOPLE.
