Isabella Dam safety project done just in time for record snowpack

April 4, 2023
by Lois Henry
Congressman Kevin McCarthy at a ceremony marking completion of the Isabella Dam safety project in April 2023. Lois Henry / SJV Water
Lois Henry

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Speaker after speaker on Tuesday noted the years long construction project to increase safety on Isabella Dam was completed this past October – just in time.

Robert Gomez, Chairman of the Tubatulabal tribe, gives an invocation at the start of Tuesday’s dedication ceremony of the Isabella Dam repair project. Lois Henry / SJV Water.

With a snowpack at 422% of normal, the  reservoir is expected to hit its full capacity of 568,000 acre feet, and then some. Water content in Kern River watershed is estimated at 1.8 million acre feet, which means even at full capacity, Isabella Lake will have to empty and refill several times.

Water is expected to be released from both the dam’s river valves and its spillway, possibly reaching 9,000 cubic feet per second through June and July, according to Kern River Watermaster Mark Mulkay.

Maximum capacity in the lake had been kept to 360,000 acre feet since 2006 when a study revealed the dam was vulnerable to overtopping, seepage and seismic damage.

The Army Corps of Engineers, which owns and operates the dam, began construction in 2018. A final piece of the project, replacing a Forest Service visitor center, will be completed this time next year.

The Corps made improvements to the main and auxiliary dams and, perhaps the most noticeable, built a massive accordion shaped “labyrinth weir” to prevent overtopping.

“I’ve gone through four administrations, but we got it done,” said House Speaker Kevin McCarthy at Tuesday’s ribbon cutting for the nearly $300 million project. “No more studies, no more waiting. And if we all came back here in a month, we’d be underwater.”

He referenced the fact that the ceremony was held at a boat launch where water is already creeping up.

The “labyrinth” weir is probably the most noticeable piece of the Isabella Dam safety project. Lois Henry / SJV Water

SJV Water is an independent, nonprofit news site dedicated to covering water in the San Joaquin Valley. Get inside access to SJV Water by becoming a member.


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