Marin Water Pursuing Largest Water Supply Measure in 40 Years by Marin Water Mar 10, 2025 Member Submitted News CORTE MADERA– The Marin Water Board of Directors has directed District staff to proceed with design and environmental review for a new conveyance pipeline and pumping plant that will bolster water supply reliability in times of drought by diverting excess winter water from Sonoma County’s Russian River to a local Marin Water reservoir. At 1,485 square miles, the Russian River Watershed is 40 times larger than the watershed feeding Marin Water’s seven local reservoirs, capturing tremendous amounts of water during winter rainfall events, often swelling and frequently flooding. Records show that even during drought years there are plentiful “winter water” supplies in the Russian River between October and May resulting from winter rainfall, even after accounting for the in-stream water required to support aquatic life. This winter water source is not reliant on Sonoma County’s stored supply but instead capitalizes on rainfall and excess river flows, which currently stream out to the Pacific Ocean. If ultimately constructed, the project would provide the infrastructure needed to capture and move excess water to be stored in Marin Water’s reservoirs for later use, adding to the resilience of the North Bay’s overall water supply during droughts. The project proposes a pumping plant and a 36-inch-wide pipeline running 13.2 miles from the North Marin Aqueduct to Marin Water’s Nicasio Reservoir. During dry years, the new infrastructure could replenish the District’s local water supply with as much as 3,800 acre-feet of stored water. Potential future phases of this project could increase replenishment of stored water to up to 8,100 acre-feet. The project would mark the District’s largest water supply resiliency project in 40 years. “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 Matt Samson, Marin Water Board President. “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.” The Board’s Tuesday action marks a significant milestone within the District’s Integrated Water Supply Roadmap efforts and was coupled with a directive to continue work on the following other water supply resiliency measures outlined in the Roadmap: • Partnering with customers through robust and innovative water efficiency programs, which have already helped reduce future annual water needs by 2,000 acre-feet. • Investigating the feasibility of expanding local reservoirs, with a focus on modifications to existing spillways and possible expansion of Kent Lake. • Monitoring desalination technological advances and cost. Pursuing opportunities for grant funding or public-private partnership funding for recycled water projects. • Identifying and evaluating other potential water supply opportunities, such as groundwater banking, as they arise. • Developing deeper understanding of the current state of science on climate change, including the rate of change and potential effects on water resources. The Board’s action, which could set the stage for the largest water supply project since Kent Lake was expanded in 1982, comes amid other ongoing water supply resiliency efforts, including design and environmental review work to raise the spillway at the Nicasio Reservoir and implementation of other in-system improvements that will generate additional increases in the District’s available water supply. The planned conveyance pipeline and new pumping station, as well as the additional measures being pursued, are the result of efforts started amid the recovery from the District’s 2021 water shortage emergency. Those efforts included the launch of a strategic water supply assessment, which guided the development of an integrated Water Supply Roadmap. The Roadmap is organized into five broad strategies, each with a range of projects, that – when integrated – are designed to address the District’s water supply needs to ensure a more resilient system. Learn more about the Winter Water Conveyance Project and the rest of the Water Supply Roadmap work the District is implementing to secure a resilient water supply for its customers now, and in the future, by visiting marinwater.org/WaterSupplyRoadmap.
