Dear Friends and Supporters,
Last month’s newsletter on the Atmospheric River Capture (ARC) Project generated a great set of questions from readers. This month, I want to address one of the thoughtful and important questions I received.
Q: How often will Marin Water actually need to turn on ARC?
A: Not often. And that’s exactly the point.
Let me explain why this is good news, not a problem with the project.
The Historical Record
Since 1984, when Marin Water achieved its current reservoir capacity following the expansion of Kent Lake, we’ve experienced only two drought periods severe enough to deplete our reservoirs to levels that would have warranted importing additional water:
- The late 1980s drought
- The 2020-2022 drought
That’s twice in roughly 40 years. In most years, our reservoirs capture enough rainfall to meet customer needs without supplemental supplies. ARC isn’t designed for everyday use: it’s designed for the rare dry periods when our local supply isn’t enough.
ARC as Water Supply Insurance
The best way to think about ARC is as insurance for our water supply.
You buy homeowner’s insurance hoping you never have to use it. You pay car insurance premiums year after year, often without filing a claim. But when disaster strikes, insurance is what stands between you and catastrophe.
ARC works the same way. It’s the infrastructure that protects us from the water emergency we came dangerously close to during 2020-2022, when our reservoirs dropped to critical levels and emergency water supply options were limited, expensive, and uncertain.
Like good insurance, ARC offers peace of mind. We hope we won’t need it often. But when the next severe drought comes (and it will!) ARC ensures we have a reliable source of water to draw on.
Why ARC Is the Right Insurance Product for Marin
Not all water supply solutions are created equal, and the right choice depends on the problem you’re trying to solve.
Areas with chronic water shortages, where demand routinely exceeds local supply year after year, must consider solutions like:
- Desalination plants that convert seawater to drinking water
- Large-scale wastewater recycling that purifies treated wastewater for reuse
- Major long-distance water imports with continuous operations
These technologies are powerful, but they share a common characteristic: high operating costs, year in and year out. They require constant energy inputs, intensive treatment processes, and continuous staffing, whether you need the full output or not. For regions like Southern California or parts of the Central Valley that face ongoing supply deficits, these costs are justified because the infrastructure is used constantly.
Marin’s situation is different. We face intermittent shortages during severe droughts, not chronic supply deficits. We don’t need a solution that costs millions of dollars to operate every year; we need a solution that’s ready when drought strikes but doesn’t burden ratepayers in normal years.
The Cost-Effectiveness Case
This is where ARC’s design really shines:
During normal and wet years (the majority of years): ARC sits idle. Operating costs are minimal – essentially just maintenance of the pipeline infrastructure. Customers don’t pay to run a system they don’t need.
During drought years: ARC activates, drawing surplus winter water from the Russian River into our reservoirs. We pay operating costs only when we’re actually using the water – exactly when the value of that water is highest.
Compare this to a desalination plant, which would require ongoing energy and operational expenses every single year regardless of whether we’re in drought, with much higher costs to build and maintain. For a region that needs water supply backup only intermittently, ARC delivers better value per dollar invested.
Matching the Solution to the Problem
Good water planning means choosing the right tool for the job. A region with chronic shortages needs continuous-use infrastructure. A region like Marin, with strong conservation programs, reliable local supplies in most years, and occasional severe droughts, needs cost-effective insurance against the worst-case scenarios.
That’s ARC.
But It’s not the only water supply solution we’ll ever need: we will continue to expand our water supply portfolio, and we’ll continue investing in conservation to reduce demand. But as a next step for protecting Marin from intermittent severe droughts, ARC is the right answer.
The Bottom Line
When someone asks “how often will we use ARC?”—the answer is “hopefully not often, but always when we need it.” That’s what makes it a smart, cost-effective insurance investment for Marin’s water future.
I’ll continue answering reader questions in future newsletters. If you have questions about ARC or any other aspect of Marin Water’s operations, please send them my way.
Thank you for engaging with these important issues. Your thoughtful questions make our work better.
Sincerely,
Ranjiv
Director, Marin Municipal Water District
Candidate for Re-election, November 2026