Marin Water is planning a pipeline and pumping station to divert excess winter rainfall into its reservoirs from the Russian River watershed that now flows into the Pacific Ocean.

The project would send water from Sonoma County's Russian River through a 36-inch pipeline, 13.2 miles from the North Marin Aqueduct to Marin Water's Nicasio Reservoir, the water board said Friday in a press release.

Plans for the pipeline and pumping station are a reaction to the district's 2021 water shortage emergency and would be the largest water supply resiliency project in 40 years, the district said.

"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," the district said. An acre-foot is a volume of water that would cover one acre to a depth of one foot.

The district's reservoirs are capable of holding 79,566 acre-feet of water, according to the district's website.

The Marin Water Board of Directors on Tuesday directed district staff to proceed with design and environmental review for the project.

The Russian River watershed often swells and floods from winter rainfall that streams out to the Pacific Ocean, the board said. At 1,485 square miles, it is about 40 times larger than the watershed feeding Marin Water's seven local reservoirs.

"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," Marin Water President Matt Samson said in the press release.

"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 supplies to further protect us from severe drought," he said.