Water gushes down spillway of America's tallest dam for 1st time in 2 years
Water is flowing down the spillway of the nation's tallest dam for the first time since it crumbled during severe flooding in 2017 and threatened to flood California communities. The billion-dollar renovation of Oroville Dam is considered the biggest and fasted project in state history.
For the first time in two years, water is flowing down the main spillway of the Oroville Dam, the tallest in the nation.
The California Department of Water Resources (DWR) opened the flood-control spillway at the Oroville Dam in Butte County, California, on Wednesday, April 3. The newly constructed main spillway has not been used since it crumbled in early 2017 following frequent heavy soaking storms that winter, threatening to flood California communities, including Oroville.
“The decision to use the main spillway was the result of following the normal operations plan to help provide flood protection to downstream communities.” Joel Ledesma, an official at the DWR, said in a media briefing on Tuesday.
Officials released 3,300 cubic feet per second (cfs) on Tuesday at 11 a.m. PDT, which sent a thin sheet of water down the newly repaired main spillway. The flowing water poured into the river below, forming small waves and crashing into concrete barriers.
Around 4 p.m. PDT on Tuesday, DWR increased the flow down the main spillway to reach about 8,300 cfs. Total releases to the Feather River will remain at approximately 20,000 cfs, the CA-DWR said in a tweet.
DWR staff monitored the release of the water, some from atop the Lake Oroville flood control gates.
It's been an unusually wet winter in California, and more storms will strike the region in the coming months. Snowpack also remains high throughout the state. On Tuesday, a snow survey at Phillips Station found snowpack at 200% of average, and statewide snowpack is 162% of average. It was the fourth survey conducted this year.
State officials said they need the spillway to control the rising water in the lake behind the dam. Lake Oroville is one of the state's key reservoirs.
“We are releasing water to make room for that snowpack and inflows for rainfall on the horizon,” Molly White, an official at the DWR, said in the media release.
In early 2017, the dam's half-century-old spillway broke apart as it carried heavy flows from storms. A hole the size of a football field and 40 feet deep developed due to erosion. In February 2017, nearly 200,000 Oroville residents were evacuated amid flood fears.
“Protecting communities from flooding is a vital part of the Department’s mission,” CA-DWR Director Karla Nemeth said in the press release. “Today, we inaugurate the reconstructed spillway to serve that essential purpose and to prepare us for the future.”
Excess water release has damaged the spillway at the Oroville Reservoir Dam this winter. This photo was taken on Feb. 7, 2017. (Kelly M. Grow/California Department of Water Resources)
The renovation is considered the biggest and fastest construction project in state history. It required enough concrete to fill more than 370 Olympic-sized swimming pools.
“We’re confident that this spillway has been redesigned using today’s best modern technologies and engineering to accommodate for what led to February 2017,” Mellon said.
The state spent more than $1 billion on repairs, reinforcing the concrete with 12.4 million pounds of reinforcing steel and approximately 7,000 anchors.
“We expect it to work and we’re ready,” Ledesma said.
Work on the emergency spillway is expected to be finished later this year.
The DWR may increase flows to the Feather River again later this week to between 40,000 and 60,000 cfs to prepare for forecast inflows. Officials also anticipate potential further releases to manage snowmelt and lake elevations later this spring, according to the press release.
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