Officials Have A New Plan To Tackle Winter Flooding In Marin County

MARIN COUNTY, CA — Marin Water plans to lower Phoenix Lake beginning this to create extra capacity for storm runoff, a joint effort with Marin County officials aimed at reducing flood risk in San Anselmo and Ross during early winter storms.

Pumping was expected to begin Monday, after equipment modifications scheduled for Oct. 19-23. Operations could continue into mid-November, depending on weather conditions and water quality, Marin Water and the county announced.

The effort builds on a 2021 storm, when the lake’s lower water level provided room to capture runoff that otherwise would have flowed into Ross Creek and eventually Corte Madera Creek. Officials hope lowering the reservoir ahead of this winter could provide similar storage capacity, though the benefits will depend on the timing and intensity of storms and the lake’s water level when rain arrives.

“For neighbors who have experienced flooding, another winter can bring real worry about their homes, businesses and families,” said Brian Colbert, Marin County supervisor. “We appreciate Marin Water’s willingness to work with us on a practical opportunity that could help.”

Marin Water will retain control of reservoir operations, including how far to lower the lake and when to stop pumping. The agency must balance the effort with its responsibility to provide safe, reliable drinking water to more than 191,000 people and businesses throughout central and southern Marin County.

“Phoenix Lake offers an opportunity to explore how reservoir operations might provide an additional community benefit,” said Ranjiv Khush, Marin Water director. He said the agencies are drawing on lessons from 2021 while seeking to reduce downstream flows and flood risk.

Marin Water General Manager Shaun Horne said drinking water responsibilities will continue to guide operational decisions, while the effort could provide multiple benefits, including additional storage before winter storms.

The project is one part of broader winter preparations and will not eliminate the risk of flooding in San Anselmo or Ross. Officials urged residents and businesses to continue preparing their properties and emergency plans.

“Reducing flood risk takes sustained work and a willingness to look at every practical opportunity,” said Marin County Executive Derek Johnson, thanking Marin Water for its partnership.