Lake Berryessa's distinctive funnel-shaped spillway has roared to life for the first time since 2019, following intense atmospheric rivers that drenched Northern California this week.
The rare spectacle at the Napa County reservoir drew dozens of onlookers Wednesday morning to witness water cascading down the 72-foot-wide concrete structure, locally known as the "glory hole."
"People were taking pictures and videos and just standing in awe," said Peter Kilkus, editor of the Lake Berryessa News, who observed the phenomenon alongside other spectators.
The unique drainage system, technically called a morning glory spillway due to its flower-like shape, is one of only a few such structures in the United States. It functions similarly to a bathtub drain, preventing the reservoir from overflowing by channeling excess water through the funnel and into Putah Creek on the other side of Monticello Dam.
This activation marks only the fourth time the spillway has been engaged in the past two decades, with previous occurrences in 2019, 2017, and 2006. According to Jay Cuetara, supervising water resources engineer for the Solano County Water Agency, the combination of two consecutive wet winters and recent heavy rainfall finally pushed the reservoir to its spilling point.
The man-made Lake Berryessa, created in 1958 by the construction of Monticello Dam, serves as a critical water source for neighboring Solano County's residents, businesses, and agricultural operations.
For those interested in witnessing this remarkable engineering feature in action, officials expect the spillway to remain active through the weekend and potentially for several more weeks.
The reservoir's distinctive spillway design was necessitated by the narrow canyon geography, which couldn't accommodate a conventional dam spillway configuration. This unique solution has since become one of the lake's most recognizable features, drawing visitors from across the region whenever it activates.