Corte Madera, Calif., water district plans 13-mile pipeline to boost drought supply

(UI) — Marin Water is moving ahead with design and environmental review for a 13.2-mile underground pipeline and new pumping station aimed at improving drought resilience by redirecting excess winter flows from the Russian River into local reservoirs.

The Marin Water Board of Directors on Feb. 25 voted to advance the planning phase for what would be the district’s largest water supply infrastructure project in more than four decades.

The proposal calls for construction of a 36-inch-wide pipeline from the North Marin Aqueduct to Marin Water’s Nicasio Reservoir. The system would capture surplus winter runoff from the Russian River Watershed — an area 40 times larger than Marin’s own — and store it for later use during dry years.

During drought conditions, the pipeline could deliver up to 3,800 acre-feet of water annually. A potential second phase of the project could increase capacity to 8,100 acre-feet per year. The district last undertook a water project of this magnitude in 1982, when Kent Lake was expanded.

“This conveyance project is the most appropriate and logical next step for Marin Water to take in support of a comprehensive solutions package aimed at addressing the water supply needs of our customers,” said Board President Matt Samson. “The project’s implementation timeline will allow us to increase our water supply within a few years, buying time while we focus on additional projects that will ultimately provide sufficient water supplies to further protect us from severe drought. The project also offers the district flexibility when evaluating additional large-scale projects, contributing to the overall resilience of our water supply.”

Water collected through this pipeline would not come from Sonoma County’s stored supply but from seasonal “winter water” — rainfall-driven flows that typically flood the Russian River during wet months and eventually flow into the Pacific Ocean.

The board’s February decision marks a milestone in the district’s long-term Integrated Water Supply Roadmap, which was developed in response to the 2021 water shortage emergency. The plan outlines five core strategies, each with multiple projects aimed at strengthening the district’s water system against climate-driven variability.

In addition to the pipeline and pumping station, the district is pursuing other resiliency measures, including:

• Water efficiency programs, which have already reduced future annual water demand by 2,000 acre-feet.
• Reservoir expansion feasibility studies, including spillway modifications and possible Kent Lake enlargement.
• Exploration of recycled water and desalination, including funding options and technology tracking.
• Evaluation of additional water sources, such as groundwater banking.
• Continued monitoring of climate science to better understand long-term resource impacts.

Separately, Marin Water is also evaluating infrastructure upgrades such as raising the spillway at Nicasio Reservoir and other in-system improvements designed to increase available water storage.

The Winter Water Conveyance Project reflects an effort to use regional resources more efficiently and support long-term water security in the North Bay.

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