LAKE ISABELLA, Calif. (KERO) — According to the US Army Corps of Engineers, April 1 is the start of the 2023 runoff season, including the flow from Lake Isabella into the Kern River. The corps has limited the capacity of the lake since 2006 due to safety issues with Isabella Dam.
Repairs to the dam, which began in 2017, are essentially complete, and the Army Corps of Engineers have plans in the works to restore the lake to its original capacity. Jeremy Croft with the corps says they're hoping their fill plan will be approved so they can begin filling the lake throughout this spring and summer.
According to Croft, three categories of safety issues were identified following the USACE 2006 study of Isabella Dam: hydrologic over-topping, meaning when water comes over the top of the dam, seepage, which is when water comes under the dam and causes a wet spot or a puddle on the downstream side, and seismic risk because there is a fault line that runs under the auxiliary dam at Lake Isabella.
These issues prompted the corps to downgrade the dam's safety rating.
We have what we call Dam Safety Action Classifications, and they go from 1 to 5. If you have a DSAC 5, that is the safest dam, and then a DSAC 1 is the least safe,” explained Croft.
Croft says the Isabella Dam was identified as a DSAC 1, least safe, and when that happens, they have to implement risk reduction measures. One of those measures includes limiting the amount of water they can store in the lake, what they call “restricted pool.”
"Restricted pool is about 361,000 acre feet, and that is about a 200,000 acre foot difference from the normal operational capacity at Isabella, which is about 568,000 acre feet," said Croft.
“According to Croft, the deviation request allows USACE to proceed with the fill plan, which is a step in the process of testing, monitoring, and validating the safety features of the dam to ensure USACE has ultimately accomplished their mission.”
He adds that in order to raise the safety rating of the dam, the restricted pool needs to be lifted.
"It's going to happen eventually, but even if there's a delay in lifting that, temporarily or permanently, we are authorized to temporarily exceed the restricted pool if necessary for flood-management reasons. That is something that our existing policy allows us to do," said Croft. "We don't need the deviation requests or a fill plan to be approved in order to achieve that."
Kern River Watermaster Mark Mulkay says that with the significant rainfall the county has seen for the past few weeks, the Kern River past Lake Isabella has seen 3,600 cubic feet per second coming out of Isabella, and says their goal is to ramp those levels up.
Mulkay says this is going to be an opportunity to recharge the groundwater basins while providing plenty of water for the City of Bakersfield and for agriculture.
"They're going to go up," Mulkay says of the water levels. "We're working with the Corps of Engineers to make sure that the levels are set right and the approvals are reached. We'll probably, within the next week to 10 days, be up around 5,400 (cubic feet per second) coming out of the reservoir."
Mark Mulkay, Kern River Watermaster, on the Kern River
People are going to see it through the city and think, 'Oh boy, this looks so fun! We need to go out and play in it!'
There's trees in it, there's brush in it, there's all kinds of things underneath that water. People need to be very careful when they're around the river this year.
There's going to be more water than they've seen in a long time and they just really need to protect themselves.
