Monte Rio Beach was among the spots closed by the upstream Guerneville sewage spill in 2025. (Roger Coryell/Sonoma County Gazette)

When the Russian River flooded in early January, the wastewater treatment plant outside Guerneville flooded with it. Millions of gallons of untreated sewage spilled into the river over two days. Beaches closed. Warning signs went up. Residents and visitors were told to stay out of the water.

Sonoma Water, which operates the facility, warned that untreated wastewater “contains bacteria, viruses, and other pathogens that can cause illness,” and said contact poses particular risks for children, pets, older adults and people with weakened immune systems.

For people, the advice was clear. For the river, there was no choice.

When raw sewage enters a river, especially during a flood, the damage isn’t always obvious. There were no confirmed fish kills reported after the January spill. Officials monitored the river, but the water was high,

fast and muddy. If fish died, they would have been difficult to spot. That’s often the case during winter spills, when floodwaters dilute pollution and carry it downstream quickly.

But the absence of dead fish doesn’t mean the river escaped unscathed.

Raw sewage carries a heavy load of organic waste and nutrients. As bacteria break that material down, they consume oxygen in the water. In slower channels and backwaters, oxygen levels can drop enough to stress fish, especially juveniles. Salmon and steelhead — both present in the Russian River watershed — are particularly sensitive at early life stages. Eggs need clean, oxygenated gravel. Cloudy water and low oxygen can smother them or slow development.

Even adult fish often respond by leaving. Studies from other river systems show fish clearing out of spill zones for weeks after major sewage overflows. They don’t wait around to see if conditions improve.

When fish move, everything else follows.

River otters don’t stay where prey disappears. Birds that hunt fish and aquatic insects move on. Amphibians, which absorb water through their skin and lay eggs directly in the river, are even more vulnerable to contamination. Sewage also carries the modern extras — household chemicals and pharmaceuticals — that rivers were never designed to handle. Those compounds don’t always kill wildlife outright. Sometimes they interfere with reproduction, growth or immune systems in ways that show up later as fewer fish, fewer frogs and a river that feels quieter than it used to.

Sonoma Water said part of the discharge traveled about a quarter mile through forest before reaching the mainstem of the Russian River. That detail matters. The spill didn’t simply pass from pipe to river. It moved through habitat, touching soil, roots, insects and small animals before it ever reached open water.

The spill stopped at 6:50 a.m. Jan. 8, Sonoma Water said, once floodwaters dropped enough for operators to regain control. Water testing continued for days. Advisories were lifted after samples met state standards.

On paper, the emergency ended.

But river towns live with the aftereffects longer than that.

The lower Russian River is the backbone of a tourism-driven economy. Guerneville, Monte Rio and Jenner depend on summer weekends, on people swimming, floating, fishing and renting cabins near the water. Tourism isn’t a bonus here. It’s how the towns survive.

News that millions of gallons of untreated sewage spilled into the river doesn’t fade as fast as bacteria counts. People remember it. They talk about it. They look it up when they’re deciding where to bring their kids in July.

Local officials know this. That’s why reopening beaches as soon as testing allows is always urgent. But there’s a difference between water being technically safe and people feeling comfortable getting into it. A river only has to earn a bad reputation once.

Sonoma County Supervisor Lynda Hopkins, whose district includes Guerneville, tied the spill to long- standing design limits at the facility.

“In my opinion, this facility was built poorly in the first place and was never equipped to really handle the amount of rain that we can get,” Hopkins said in an interview with KQED.

She said the storms driving these failures are no longer rare events.

“We just simply do not have the capacity to handle these severe atmospheric storm events,” Hopkins said.

Fixing that problem won’t be cheap. Hopkins said local ratepayers can’t cover the cost of major upgrades on their own and that state and federal funding will be needed.

“We’re really going to be looking to state and federal funds to come up with a long-term solution,” she said.

People often ask why a treatment plant was built on a floodplain in the first place. The answer isn’t stupidity. It’s geography and history. That’s where the flat land was. That’s where gravity worked. That’s where it was affordable decades ago. At the time, planners assumed major floods were rare enough to accept the risk.

The river has changed that math.

The January spill didn’t produce dramatic images of dead fish lining the banks. What it produced instead was another reminder that the Russian River is being asked to absorb failures it wasn’t built for — and neither were the systems around it.

If Sonoma County wants a living river — one with salmon, otters, insects and people in inner tubes — sewage spills can’t be treated as isolated emergencies. They’re warnings. About infrastructure. About climate. And about how much damage a tourism economy can absorb before people quietly decide to go somewhere else.

When the river gets sick, it doesn’t always die.

Sometimes it just loses trust.