It’s the time of year, when a massive 100-foot rubber dam emerges from the bottom of the Russian River near Forestville. That’s to ensure the 600,000 residents of Sonoma and Marin counties who rely on the river for drinking water have a stable supply during summer, when demand for water increases but river levels are lower.
Monday marked the start of the three-day process of raising the dam, which was first raised in the 1970s. Throughout the year, six caissons — or wells — dig 100-180 feet beneath the riverbed to draw up water, which is filtered by gravel along the bottom of the waterway.
“The primary source of our water is the Russian River,” said David Royall, assistant general manager for operations and maintenance for Sonoma Water. “We have to maintain a fixed elevation inside of our caissons. Once it gets to 15 feet, that’s when we make the call.”
Seasonal dams like the Russian River’s tend to be a less invasive alternative for local wildlife than their permanent counterparts. A “fish ladder” over the dam helps local species, including Coho and Chinook salmon, continue their migration to and from spawning sites on the river.
Most of the year, residents of the area consume 20-40 million gallons of water a day. At the height of summer, consumption can reach up to 60 million gallons a day. California’s 2020-2023 drought brought conservation efforts that have significantly impacted water use.
“The demand isn’t as high,” said Royall.
In the 1990s, he said, daily consumption was typically at 90 million gallons. But conservation efforts like trip irrigation, efficient water fixtures and people getting rid of lawns have helped halve that number.