SLO County wins another battle in the war over Lopez Lake water

July 3, 2026

Lopez Lake

By KAREN VELIE

San Luis Obispo County successfully stopped another attempt to increase the amount of of water it releases from the Lopez Lake Dam each year with a goal of protecting threatened steelhead trout through an emergency order.

The county argues the increased water flow would reduce the water supply to thousands of people and also harm two endangered species. Lopez Lake not only provides water for Arroyo Grande, Grover Beach, Pismo Beach, Oceano and Avila Beach, it is also used to fight wild fires.

In Dec. 2024, a U.S. district judge sided with four environmental groups with a goal of protecting steelhead trout, a threatened species. She ordered San Luis Obispo County to increase the amount of water it releases from the Lopez Lake Dam each year.

The county appealed the ruling, arguing possible impacts on the California red-legged frog and tidewater goby—both endangered species. In late 2025, the 9th Circuit Court of Appeals vacated the 2024 ruling.

The four environmental groups fired back with a motion for a preliminary injunction seeking :

• Release water from Lopez Reservoir at rates the county argued would be unsustainable.
• Revise the county’s habitat conservation plan and construct several capital projects outside the habitat conservation plan review and approval process.
• Place implementation under court oversight through a special master and expert panel.

On June 29, the judge rejected the motion which was based on an the environmental group’s argument that releasing more water would not harm the California red-legged frog and tidewater goby, and might even benefit the two endangered species.

In its response, the county questioned the legitimacy of the group’s expert witness while noting the increased water flow could displace the endangered species’ eggs and juvenile stealhead trout are known to eat the eggs.

“The court recognized that extraordinary injunction requests like these require extraordinary proof, which the plaintiffs did not provide,” said SLO County Counsel Jon Ansolabehere. “The plaintiffs were asking the court to order sweeping operational changes before the case is even decided, without sufficient evidence that those changes would not harm other federally protected species.”

Meanwhile, the case is still proceeding through the court system, with the cost of the more than $4.5 million lawsuit to be covered through water rate increases.

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