Phoenix Lake Plan Aims To Reduce San Anselmo Flood Risk

SAN ANSELMO, CA — Marin County and Marin Water plan to lower Phoenix Lake's water level to help reduce flooding in San Anselmo and Ross ahead of winter storms.

Marin Water scheduled pumping to begin Monday, following equipment modifications planned for Oct. 19-23. Operations are expected to continue into mid-November, depending on weather conditions and water quality.

The effort would create more room for storm runoff before it reaches Ross Creek and Corte Madera Creek, potentially reducing downstream water levels, according to an Oct. 22 county news release.

During an October 2021 storm, lower lake levels helped capture runoff that otherwise would have flowed into downstream creeks. Officials hope the same approach will help limit flooding during early winter storms, although its effectiveness will depend on rainfall patterns and available reservoir capacity.

“For neighbors who have experienced flooding, another winter can bring real worry about their homes, businesses and families,” Marin County Supervisor Brian Colbert said in the release.

Marin Water will oversee pumping operations and monitor weather and water quality throughout the process. The agency will also determine how far to lower the reservoir and when to stop pumping, balancing flood-reduction efforts with its responsibility to maintain a reliable drinking water supply.

Although the additional storage could help reduce downstream flooding, officials cautioned that it would not eliminate the risk in San Anselmo or Ross. Residents and businesses should continue preparing for winter storms.