Body of News Release
Marin County, CA – Marin Water and the County of Marin are working together on an effort to lower Phoenix Lake ahead of the 2026 winter season, creating additional room to capture stormwater to help moderate downstream flows during early winter storms to help reduce creek levels and flood risks in San Anselmo and Ross.
Marin Water is preparing to begin pumping October 26, following pump modifications scheduled for October 19–23. Pumping is expected to continue into mid-November, with weather conditions and water quality guiding Marin Water’s decision about when to conclude operations.
The effort brings together the County’s work to reduce flood risk and Marin Water’s expertise in managing its reservoirs and drinking water system. Marin Water will retain responsibility for all reservoir operating decisions, consistent with its mission to supply, treat and deliver safe, reliable drinking water to more than 191,000 people and serve businesses throughout central and southern Marin County.
“For neighbors who have experienced flooding, another winter can bring real worry about their homes, businesses and families,” said Marin County Supervisor Brian Colbert. “We appreciate Marin Water’s willingness to work with us on a practical opportunity that could help.”
Past experience offers a reason to pursue the approach. During an October 2021 storm following the drought, Phoenix Lake’s lower water level provided room to capture runoff that otherwise would have flowed into Ross Creek and, ultimately, Corte Madera Creek. Lowering the reservoir before this winter could create similar storage capacity, although the benefit will depend on the timing, intensity and duration of storms and the lake’s water level when rain arrives.
“Phoenix Lake offers an opportunity to explore how reservoir operations might provide an additional community benefit,” said Marin Water Director Ranjiv Khush. “By working with the County and drawing on what we learned in 2021, we can take a thoughtful approach to potentially reducing downstream flows and flood risk while respecting the reservoir’s role in our water system.”
Marin County Supervisor Denis Rodoni added, “Partnerships give us the opportunity to look at familiar challenges in new ways. By bringing together Marin Water’s expertise in managing our drinking water supply and the County’s flood protection experience, we’re exploring a creative approach that could help our communities this winter. That willingness to work together and find practical solutions is what our residents expect and deserve.”
Marin Water staff will monitor weather and water quality throughout pumping operations. Decisions about how far to lower the lake and when to stop pumping will remain with Marin Water, based on operating conditions and drinking water responsibilities.
“Our responsibility is to provide safe, reliable drinking water, and that will always guide our operational decisions,” said Marin Water General Manager Shaun Horne. “At the same time, this season’s operations give us an opportunity to achieve multiple benefits maintaining our water supply, creating additional storage capacity ahead of winter storms, and helping reduce peak flows downstream during early-season storms.”
The Phoenix Lake effort is one potential contribution to broader winter preparedness. Additional storage may help capture runoff during some storms, but it cannot eliminate flooding in San Anselmo or Ross. Residents and businesses should 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. “We value Marin Water’s partnership and the expertise its staff brings to this effort. Working across agencies allows us to connect resources and find creative ways to better protect our communities.”