DWR to test main spillway at Oroville Dam

Appeal-Democrat, Marysville, Calif.
·2 min read

Jan. 22—The California Department of Water Resources (DWR) said late last week that there would be "routine testing" conducted on Wednesday morning on Oroville Dam's main spillway gate hoist system.

According to officials, the testing will take place on Wednesday between 10:30 a.m. and noon.

"During testing, two main spillway gates will be lifted one foot, releasing approximately 800 cubic feet per second of water down the spillway chute," the DWR said. "The gates will remain open for approximately 15 minutes before being closed. Due to the minimal amount of water being released, water will appear to trickle from the chute. DWR will sound Oroville Dam's alarm prior to spillway releases and gate testing."

The DWR said Oroville Dam's eight main spillway radial gates also were inspected and tested in November 2023.

According to officials, recent storms have caused Lake Oroville's elevation to rise above the level of the spillway's main gates. As of Friday, Lake Oroville was measured at 825 feet elevation with a storage of approximately 2.49 million acre-feet, about 70% of its total capacity and 126% of the historical average.

"While the gates are closed, water may still be seen on the main spillway outlet as the seals on the eight radial gates are not designed to be watertight," the DWR said. "The seals do not play a role in the structural integrity of the gates, which continue to operate as intended. DWR periodically maintains and adjusts the seals during low-reservoir conditions to improve their sealing capability."

According to officials, as of Friday, Feather River flows remained at 650 cubic feet per second (cfs) through the city of Oroville with 1,100 cfs being released from the Thermalito Afterbay River Outlet for a total Feather River release of 1,750 cfs downstream. The DWR said it would continue to assess daily releases to the Feather River.

"Visitors to Oroville Dam may also notice minor amounts of water flowing from drains built into the emergency spillway, which is normal and expected with the emergency spillway design," the DWR said. "The dam and emergency spillway continue to operate as intended."