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Lopez Lake expected to overflow for the first time in 25 years

Posted at 10:45 PM, Mar 15, 2023

Reservoirs continue to fill up across the Central Coast, which is great news for our local water supply.

Lopez Lake is expected to overflow in a matter of days. That would send water over the spillway for the first time in 25 years.

After approaching record-low levels, Lopez Lake is now almost completely full.

“I live five or six miles away so, I come out here once in a while. It’s incredible, I love it,” said Arroyo Grande Resident John Adkins, who drove out to see the lake at its highest level in years.

He has been keeping a close eye on lake levels and is waiting for water to flow over the spillway any day now.

“I think it’s at 516.8 or something like that and 522 is the overflow into the spillway,” explained Adkins.

Lopez Lake has risen just above 516 feet in elevation and is now just six feet from overflowing.

“It’s kind of crazy to go from one of the lowest elevations that we’ve had down around 10,000-acre feet during the drought--and now, we’re almost at 100%,” said David Spiegel, who is an engineer for SLO County Public Works.

Water management officials say that the spillway will almost certainly be put to use for the first time since 1998.

“We’re projecting that it will likely spill probably in the next seven to 10 days—maybe 14 days depending on how much runoff we get,” said Spiegel.

The Lopez Lake spillway undergoes maintenance every year.

The giant concrete slabs that line the interior have been re-sealed to make sure that water doesn’t begin to erode the spillway, which prompted mass evacuations beneath Lake Oroville in 2017.

“That’s not a concern for us, but just a precautionary measure,” explained Spiegel.

Water flowing over the spillway could also lead to more flooding downstream.

“You would get an uncontrolled release. Right now, you have all that flood storage,” said Spiegel. “So, we would definitely be monitoring A.G. and Oceano, especially the levee.”

Lopez Lake was 89.2 percent full as of Wednesday evening, and plenty of runoff is still flowing downstream.