After completing a study this summer of potential new water supplies for the greater Novato area, the North Marin Water District is exploring two options to boost the storage and production of potable water at its Stafford Lake Reservoir.
The year-long study began in July 2021 after the district and the 61,000 residents of the Novato region it serves felt the pressure of two years of extremely dry conditions. The 2020-2021 rainy season was the driest on record for the district, with just 8 inches of rain falling on Lake Stafford, its only local reservoir. The lake normally sees about 27 inches of rain on average.
Additionally, the Sonoma County Water Agency, which provides 75-80% of the district’s annual supply through water imports from the Russian River, had reduced imports by 20% that summer because it faced shortages in its two reservoirs, Lake Mendocino and Lake Sonoma. The utility has since reinstated the 20% import cut this summer in response to low water supplies.
Stafford Lake is the district’s only emergency supply and is typically used during the summer when water usage can double. The lake can hold approximately 4,300 acre-feet of water and accounts for approximately 25% of Novato’s water supply.
The district also has the ability to pump water from the Russian River into the reservoir during the most plentiful winter months to hold it in reserve until needed. Anticipating a dry 2020-2021 winter, the district spent $400,000 to replenish the reservoir that winter. The gamble paid off – the lake would otherwise have dried up later that year.
Tony Williams, general manager of the North Marin Water District, said while the primary goal is to bolster Sonoma County’s supply, the Stafford Lake supply acts as a buffer in case more severe cuts are put in place. work.
“Local sourcing comes into play, especially in those situations where we have to scale back,” Williams said. “To provide some resiliency and redundancy, our Stafford supply helps us through these times. This is the main objective. It’s not 100% resilience. We can’t duplicate what we get from Sonoma Water, but it provides a bit of a buffer.
The study recommends that the district expand its local supply by up to 2,000 acre-feet to meet the water demands of projected population growth in the Novato area. According to the study, water demand is expected to increase by 2,300 acre-feet in Novato, or about 26%, over the next 25 years.
The district is investigating options to install an adjustable sluice gate on the Stafford Lake spillway that would allow the reservoir to hold an additional 726 acre-feet of water, an increase of approximately 17%. Additionally, the district is set to launch a pilot test at its Stafford treatment plant to test if there are ways to produce more drinking water and reduce waste when treating supplies from Stafford Lake. . The study estimates that this could produce 20 to 70 additional acre-feet of water per year.
Williams said the district has already earmarked $50,000 to conduct a thorough analysis of all regulatory approvals and environmental impact analyzes that may be required for the lock project.
Although the project does not involve the dredging of sediment from the lake bottom or the raising of the dam, Williams said it will likely require changes to his water rights, which would require a potentially lengthy review by the council. state waters.
“It actually looks like a very simple project, but it’s really complicated from a permitting and engineering perspective,” Williams said.
The valve would cost about $90 per acre-foot of additional storage, according to the study. By comparison, dredging Stafford Lake to add about 550 acre-feet of storage would cost $2,600 per acre-foot. According to the study, upgrades to the treatment plant would cost between $70 and $240 per acre-foot.
District board member Mike Joly said he supports these projects to provide at least some short-term relief as the district considers more regional water supply projects.
“I think for the value and for the immediacy, yes,” Joly said of his endorsement. “We need to be seen as improving our water supply for our customers. It is important.”
The cost of the valve is estimated to be around $1.5 million, which Williams says could be covered by part of a $20 million loan the district received for facility upgrades, including the $11 million upgrade to its administration building and laboratory.
The study also identified other longer-term options that may require support from other water providers, including the Marin Municipal Water District and the Sonoma County Water Agency.
These options included capturing runoff from Bowman and Leveroni Canyons. The study evaluated various options, ranging from pumping water into Lake Stafford to constructing a new dam across the canyons.
According to the study, pumping water to Stafford would yield approximately 93 to 788 acre-feet of water per year at costs ranging from $330 to $960 per acre-foot, depending on the option. The Canyons Dam would provide approximately 175 acre-feet and 753 acre-feet of water per year, respectively, at a cost of $1,700 and $800 per acre-foot, respectively.
According to the study, other options, such as a local desalination plant, were deemed unfeasible due to the high costs and regulatory approvals that would be required for a small water district. However, Joly said there may be opportunities to partner with other Bay Area water agencies to build a regional desalination plant.
“There’s an incredible irony that we could have a water problem, being next to the largest body of water on the planet,” Joly said. “It’s just something that immediately grabs your attention. But there’s a lot of work to be done for desalination.
The Marin Municipal Water District is also evaluating regional projects such as desalination as part of its own ongoing study of new water supplies.
“We partner with Marin Water as much as possible and are interested in partnering on a future project if it makes sense for something like desalination,” Williams said. “We wouldn’t do it on our own.”
For more information on the water supply study, visit nmwd.com/save-water/new-water-supplies/.