Water Efficiency Reduced Demand 

Estimated Water Supply = 2,000 acre-feet per year

Thanks to the success of ongoing water efficiency efforts since 2020, Districtwide potable water demand has remained below forecast, enabling an adjustment to the water supply goal from 8,500 to 6,500 acre-feet per year. This sustained effort, along with community support, has helped our customers achieve a water savings of 4,000 acre-feet per year, leading to a supply goal reduction of 2,000 acre-feet per year. Marin Water will strive to gain additional savings through implementation of the strategies in the District’s comprehensive and innovative Water Efficiency Master Plan. 

• Fact Sheet on Water Efficiency
• Water Efficiency Master Plan
• Water Efficiency Program and Resources

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Advanced Metering Infrastructure (AMI)

Advanced Metering infrastructure (AMI) is technology which allows customers to receive real-time data from their water meters, helping them to detect leaks or abnormal water usage and gain greater understanding of their household or business water use patterns. Marin Water is currently testing various types of this technology as it plans for a service area-wide rollout of AMI.  This system will provide a continuous link between the District and its customers via cellular networks or radio frequencies. Presently, more than 5,000 customers are already piloting AMI.  In 2025, product testing is planned to expand with a focus on fine-tuning the customer experience prior to the broader all-service area rollout. System-wide implementation of AMI is expected to be complete by 2030.

Water Loss Control 

Marin Water has a longstanding, proactive Leak Reduction Program, which uses a variety of techniques to identify and address in-system leaks to reduce water loss. A recent gap analysis helped the District to identify additional ways to potentially enhance the existing Leak Reduction program, which are being implemented or piloted as part of the District’s Water Supply Roadmap effort. 

• Acoustic Leak Detection Pilot: One of the District’s current and very successful Leak Reduction Program techniques involves the use of listening devices called leak noise amplifiers by District staff to manually survey water pipelines. The District annually inspects about 200 miles of pipeline, detecting leaks that would otherwise likely go unreported. Acoustic leak detection is the oldest and most reliable method of leak detection. But by leveraging newer advancements in technology, the District may be able to further enhance this effort and is implementing an Acoustic Leak Detection Pilot in select parts of the service area. The Pilot will test various types of technology to determine their effectiveness in improving the response rate of system leak detection and to determine if the new technology can help better address leaks. This pilot involves two neighborhoods – Santa Venetia and Spinnaker Point – and two types of acoustic leak detection systems. One system is fitted to fire hydrants for the purpose of detecting leaks in the District’s water pipelines that run between hydrants; the other is integrated with the customer meter assembly and serves the same function. Both systems are being deployed to both neighborhoods as part of the pilot program.   

Winter Water Conveyance (Atmospheric River Capture Project)

Estimated water yield: 3,800 acre-feet per year

Historical records show that, even during drought years, there are plentiful water supplies in the Russian River in Sonoma County between October and May resulting from winter rainfall – even after accounting for the in-stream water required to support aquatic life.

Right now, this excess Russian River winter water flows out into the Pacific Ocean. The Winter Water Conveyance Project could change that by providing the necessary infrastructure to divert some of this excess winter water, as needed, from the Russian River to our reservoirs to be stored for later use. This winter water source is not reliant on Sonoma County’s stored supply but instead capitalizes on rainfall and excess river flows.

Formally named the Atmospheric River Capture (ARC) Project, this project would construct a 36-inch wide pipeline running 13.2 miles from the North Marin Aqueduct (Russian River pipeline) to Marin Water’s Nicasio Reservoir. During dry years, this new infrastructure could replenish our local supply with as much as 3,800 acre-feet of stored water annually in its first phase, while a latter phase provides up to 8,100 acre-feet per year.

The process for design and environmental review for this project is now getting underway.

• Winter Water Conveyance Fact Sheet

Nicasio Spillway Modification

Estimated Increase in Water Storage Capacity = approximately 3,700 acre-feet per year 

Nicasio Reservoir was created by the construction of Seeger Dam, an earthen filled dam on Nicasio Creek in 1960. The reservoir's current storage capacity is 22,340 acre-feet. This project would install a 280-foot-long, 4.4-foot-high inflatable rubber gate spanning the width of the existing spillway crest of Seeger Dam to increase the capacity at Nicasio Reservoir by approximately 3,700 acre-feet. Modifying Nicasio Reservoir’s spillway is one of the near-term storage enlargement projects identified through development of the District's Water Supply Roadmap. 

The project is a relatively quick and cost-effective way to achieve additional water storage capacity as compared to other, longer-term water supply alternatives within the District’s Roadmap. The additional water supply yielded through this project would help increase the District's water supply resiliency during future droughts. 

• Nicasio Spillway Modification Project information webpage 

   

Other Spillway Modifications

The District continues to evaluate its other reservoir spillways to determine if there are potential opportunities to gain additional storage capacity through modifications to any of them.
 

Electrify Soulajule Pump Station

Estimated Water Supply = 420 acre-feet per year

Soulajule Reservoir is the northernmost of Marin Water's seven reservoirs, which combine provide about 75% of the District's water supply for more than 191,000 customers in central and southern Marin. Soulajule has a capacity of 10,572 acre-feet, or 13% of the local supply. 

Soulajule lacks an electrical grid connection, which makes pumping water difficult. Historically, the reservoir has only been used two times because portable diesel generators are needed to pump water from Soulajule to Nicasio Lake and onward into the system for treatment. 

This project would install direct electric power at Soulajule Reservoir to enable the regular use of the reservoir, increasing the reliability and resiliency of the District’s water supply. The electrification project would establish Soulajule as a hub that support the Districts ability to import and store additional winter water from the Russian River basin. Electrification of Soulajule enhances the distribution infrastructure by allowing the District to move water more efficiently between reservoirs.  

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Phoenix-Bon Tempe Connection  

Estimated Water Supply = 260 acre-feet per year 

Phoenix Lake is one of Marin Water's smallest reservoirs, at 411 acre-feet, however it is estimated that its inflows average 3,665 acre-feet per year. Phoenix Lake water is pumped uphill to Bon Tempe Water Treatment Plant infrequently because of logistical difficulties with temporary connections. 

This project would establish a permanent connection between Phoenix Lake and Bon Tempe reservoir to capture some of the excess inflows to Phoenix Lake that are currently being lost. This project has a secondary benefit of reducing flood danger to the communities of Ross and San Anselmo by creating storage space in the Phoenix Lake basin for floodwaters.

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Forecasting and Stream Release Automation   

This initiative aims to improve forecasting capabilities and stream release automation to better manage releases. Marin Water staff have installed streamflow measurement equipment near Shafter Bridge. Similar work is planned at Walker Creek in the third quarter of 2025 to further improve the accuracy of streamflow releases.

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Kent Lake Storage Enlargement

Estimated water yield: 5,000 acre-feet per year

Marin Water has examined storage expansion projects at Kent Lake and at Soulajule Reservoir. Both projects would yield an additional 5,000 acre-feet per year, but based on environmental and private property factors, the District is focusing its ongoing work on storage expansion at Kent Lake, the District’s largest reservoir. 

Located within a highly productive watershed, Kent Lake fills consistently with rainfall most years. Building on this proven reliability, the Kent Lake expansion project proposes to raise the existing dam at Kent Lake to increase the capacity of the reservoir by 20,000 acre-feet, making the new total capacity about 53,000 acre-feet. Rainfall would fill this additional available storage, which would serve as an emergency drought reserve. 

The District will continue to investigate the feasibility of expanding this reservoir. 

• Kent Lake Storage Enlargement Fact Sheet

Desalination 

Estimated Water Supply = 10,000 acre-feet per year

A treatment plant would be constructed along the Bayshore in San Rafael to purify bay water for use within the District’s system, delivering up to 10,000 acre-feet of water in a drought year, or about 25% of potable demand including environmental releases. The project would require significant storage and pumping to assist with integrating the treated water into Marin Water’s system to allow the plant to deliver up to its maximum rate of 10 million gallons per day. The desalination process would produce brine as a byproduct of the treatment process; that brine would be added to the existing Central Marin Sewer Agency outfall, thereby reducing the need to build a dedicated outfall. 

The District will continue to monitor desalination technological advances and cost. 

• Desalination Plant Fact Sheet

Recycled Water 

Estimated Water Supply = 81-285 acre-feet per year

A variety of potential routes for expanding recycled water use in Marin County have been reviewed, including a project involving the Sewage Agency of Southern Marin, which would yield 81 acre-feet per year, to expanded recycled water pipeline along Peacock Gap to generate an additional 285 acre-feet per year. 

The District continues to pursue outside funding opportunities for smaller recycled water projects that make sense for our service area. 

	Conveyance	Desalination Plant	Kent Lake Expansion	Soulajule Expansion
Reliability & Sustainability1	Good	Best	Good	Good
Flexibility & Resiliency2	Best	Poor	Best	Best
Schedule & Implementation3	Best	Poor	Poor	Poor
Water Quality4	Best	Good	Best	Best
Environment5	Best	Poor	Good	Good
Social Stewardship6	Best	Good	Best	Poor
Economic & Financial7	Best	Poor	Good	Good
Click thumbnails to view fact sheet detailing the benefits and challenges for each considered project.

¹ Reliability & Sustainability: Contributes to dry year supply and substantially improves reliability of the system, improving system response to disaster
² Flexibility & Resiliency: Operational flexibility and operational complexity; improves resiliency of system; integrates and maximizes regional systems
³ Schedule & Implementation: Timeframe for implementation, considering regulatory complexity and constructability; does not preclude future projects
⁴ Water Quality: Meets current and future drinking water quality standards; the water is of the same quality as existing water supplied by District
⁵ Environment: Continues to meet the District’s commitment to environmental stewardship; extent of environmental impacts during and post construction
⁶ Social Stewardship: Extent of disruption to existing land uses
⁷ Economic & Financial: Project lifecycle costs relative to water supply yield; extent to which project uses existing infrastructure

Creation of the Roadmap was guided by the Strategic Water Supply Assessment which was developed by Jacobs Engineering with support from Marin Water's project team. The final report and background on that process are below.

Strategic Water Supply Assessment Final Draft Report (May 2023)

This report was prepared by Jacobs Engineering, with review by Marin Water staff.

• Strategic Water Supply Assessment Final Draft Report (May 2023)
  • Appendix A: Previous Investigations and Reports
  • Appendix B: System Model Description
  • Appendix C: Water Management Alternatives

Goals of the Assessment

The District has initiated a strategic assessment of various water management alternatives that could support community water needs in times of future shortages. The effort is intended to:

1. Build on extensive previous water supply planning efforts and incorporate new options
2. Evaluate current risk to District’s water delivery reliability under recent and future extended drought scenarios
3. Determine a timeline for developing alternative water management options to maintain resiliency

Projects included in Assessment

• Water Transfers with Conveyance through Bay Interties
• Sonoma-Marin Partnerships
• Local Supply Enhancements
• Desalination
• Recycled Water
• Water Conservation

Related Documents

• Board Approval of Assessment (Item 9)
• Scope of Work
• Kick-off letter to community from 2022 Board President Larry Russell (Feb. 16, 2022)
• Review Jacobs Engineering Supply Alternatives Summary, presented Sept. 13, 2022