It looks pristine but Lake Windermere, the crown jewel of England’s Lake District, is a dumping ground for sewage. Writer Will Stoddart heads to France’s Lake Annecy to find out how the town cleaned up its own waters—and why Windermere can’t do the same.
Few places in Britain look more welcoming and enticing than Windermere. England’s largest lake lies among the fells of the Lake District National Park, with picturesque, wooded slopes running down to the water.
Millions of people come every year to swim, sail and kayak, or simply to let their children splash around in the shallows. I’ve brought my own daughters here on family holidays. Looking at the lake, you assume the water is pristine. It isn’t.
Every year, thousands of visitors to the Lake District, in the northwest county of Cumbria, are lulled into a false sense of security by its spectacular natural scenery, assuming the lakes are clean, their wildlife healthy and the water safe to swim in. But last year, seven-year-old Rex Earley spent six weeks in hospital fighting a serious E. coli infection after a kayaking trip on Windermere—launching from the same beach that I’d played on with my children just six weeks before.
illions of liters of treated sewage, which can still contain E. coli, have entered the lake and the rivers that feed it—from treatment works run by United Utilities, the private company that supplies drinking water and treats sewage across northwest England. When storm overflows spill after heavy rain, untreated sewage goes directly in too.
Last year’s Big Windermere Survey, run jointly by the Freshwater Biological Association and Lancaster University, took more than 1,000 samples around Windermere over two-and-a-half years, and found high levels of E. coli and intestinal enterococci around the lake in summer—when most people go swimming.
The tests along much of Windermere’s shoreline found bacteria levels consistent with ‘Poor’ bathing water quality, raising the risk of illness for swimmers who swallow the water.
This summer, we headed for the real thing: A clear Alpine lake free from the sewage discharges that still plague Windermere. Our destination was Lake Annecy in the French Alps, considered one of Europe’s cleanest lakes.
Treated sewage also doesn’t get rid of phosphorus, which acts like fertilizer for algae. Matt Staniek, a 25-year-old zoologist who founded the Save Windermere campaign, tells me Windermere is naturally a low-nutrient lake, where blue-green algal blooms should be extremely rare.
But they now appear regularly. They release toxins and when thick blooms die and rot, they use up oxygen in the water, which changes the ecology of the lake and kill fish.
Staniek calls it “the People’s Lake”, but says he no longer trusts the water downstream of sewage infrastructure. “I won’t go swimming now anywhere below it,” he says. “It’s totally unacceptable that we’re seeing any form of sewage going into these watercourses. There should be no sewage going into Windermere fullstop. And what’s happened to this point, it’s always been about short-term mitigation.”
Windermere isn’t a one-off. Dr Ben Surridge, an environmental scientist at Lancaster University in the UK, says rivers and lakes across Britain face similar problems with sewage and storm overflows—releasing untreated sewage mixed with rainwater when sewers are overwhelmed during heavy rain. Even in 2025, an unusually dry year, storm overflows in England spilled raw sewage 291,492 times, for a total of about 1.87 million hours, according to the UK’s Environment Agency.
So this summer, fed up with worrying that swimming might make my daughters ill, and having to stop them enjoying the water, we headed for the real thing: A clear Alpine lake free from the sewage discharges that still plague Windermere. Our destination was Lake Annecy in the French Alps, considered one of Europe’s cleanest lakes.
Annecy and Windermere have plenty in common: Both are mountain lakes ringed by busy towns and villages. But unlike Windermere, Annecy has no sewage being released into it. At our hotel Les Trésoms, general manager Véronique Droux says Annecy’s reputation for exceptionally clean water is vital to its tourist industry. “It’s the image of the lake that attracts visitors and makes Annecy such a jewel,” she tells me. “Businesses throughout the area benefit from that image. You never tire of it, whatever the weather.”
She’s right. The girls swam and went canoeing, both of which resulted in children ending up in the water one way or another. At Windermere, we’d never do either. And for once, I didn’t worry about what they might swallow.
But Annecy once had a sewage problem too. In the 1950s, the growing towns around the lake were sending their sewage straight into it. Phosphorus levels rose, the water began to turn green with algae, oil slicks appeared on the surface and fishermen noticed prized species, including Arctic char and whitefish, disappearing. Toilet paper and other sewage debris could be seen floating on the surface and washing up along the shores, recalls Victor Frossard, an aquatic scientist at Université Savoie Mont Blanc. Experts warned that without action, the lake could be beyond saving within 20 years.
The alarm had first been raised in 1943 by Dr Paul-Louis Servettaz, a local doctor and keen diver who had seen the pollution firsthand. He and other concerned residents spent years drawing attention to the damage, holding public meetings and pressing local politicians to act. Just like in Windermere today.
In 1957, Annecy’s mayor, Charles Bosson, helped bring eight neighboring communities together. Their ambitious plan was to build a network of sewers around the lake, collecting sewage and carrying it away for treatment downstream. The scheme was a huge financial commitment. By 1972, its estimated cost had tripled to 60 million francs, with the French government paying 40 percent and the lakeside communities finding the rest.
Annecy itself agreed to pay almost a third of the clean-up costs, even though it wasn’t the main polluter. It wasn’t an easy decision. The city’s mayor, Charles Bosson, recalled that people preferred spending money on roads and other public facilities. But the city depended on the lake for drinking water, while its beauty was vital to tourism and the local economy.
“If the French can do it, why can’t we?”
- Matt Staniek, zoologist, Save Windermere campaign
With strong political backing, work quickly started. By 1964, the first treatment plant opened, with the full works completed by 1976. Rather than sewage going back into the lake, the new pipes intercepted it from homes and businesses and carried it away for treatment—the treated water was released downstream into the River Fier.
As sewage was diverted away from the lake, the floating waste disappeared. But cleaning up the water took longer. Frossard says it was another 10 to 20 years before phosphorus levels fell and the water became clear again. Pollution trapped in the lakebed persisted until the 2000s.
Lise Camus-Ginger, who manages two nature reserves on the lakeshore for the conservation organization CEN Haute-Savoie, says the sewer system “considerably cleaned up the lake” and played a real part in protecting its ecosystem.
France has done something similarly ambitious in Paris. Swimming in the Seine was banned for more than a century. But after heavy investment in sewers, treatment works and stormwater storage ahead of the 2024 Olympics, the river now has public bathing sites.
Nor is Annecy the only lake to have been cleaned up this way. In the 1960s, Seattle built more than 100 miles of interceptor sewers to divert wastewater away from badly polluted Lake Washington. Yet with successful examples in France and America, why has it taken so long for Windermere, one of Britain’s best-loved natural landmarks, to consider doing something similar?
The impact of inaction could have a huge economic impact too. A 2021 assessment by the Environment Agency and Cumbria Tourism, the region’s official tourism body, estimated that if Windermere’s water quality deteriorated, the local tourism economy could lose up to £122 million a year, putting up to 2,304 jobs at risk.
For the past five years, Save Windermere’s Staniek has been fighting to stop sewage entering the lake. At first, he says, United Utilities was reluctant even to release information about its sewage discharges. Getting answers was “like drawing blood from a stone”, he says. When he first proposed taking sewage out of the lake altogether, he was told it was impossible. But the example of Annecy was too powerful to ignore. “If the French can do it, why can’t we?” he tells me.
Eventually, United Utilities gave in after a nationwide campaign exposing Windermere’s pollution and produced a feasibility study in 2024.
It estimated that removing all wastewater discharges from Windermere could cost between GBP£3.5 billion (USD$4.3bn) and GBP£6.4 billion (USD$8.5bn). Preliminary plans included 42 miles (68 kilometers) of new main sewer, more than 200 miles (322 kilometers) of additional pipes to connect private septic tanks, all to be piped to a new treatment works near Grange-over-Sands, on the coast around 15 miles south of Windermere, then discharged into Morecambe Bay through a 3.7-mile (six-kilometer) pipe extending out to sea.
A new engineering study, due to be published on October 21 this year will provide a more detailed assessment. Even then, funding, planning permission and environmental approvals will be needed before construction can begin.
Staniek believes sewage discharges could be eliminated within seven years of work beginning. And the good news is United Utilities is now firmly behind the project, with its chief executive determined to make it happen, he says. “They want to deliver this.”
However, the biggest remaining hurdle is getting politicians and regulators to back the investment and push the plans forward, Staniek tells me. Without that commitment, he warns, the next stage could take another 25 years. He’s frustrated that it’s taken so long. “It shouldn’t take … a 25-year-old standing up and campaigning. It should have happened 30 years ago.”
It shouldn’t be that hard: “The French effectively went, ‘This is terrible. We should stop doing it.’ And so they stopped,” he says.
When Dr Paul-Louis Servettaz began campaigning to save Annecy in the 1940s, he faced years of scepticism. But he persisted: “We had to clean it up, or leave future generations a polluted lake.”
More than 80 years after his campaign began, Windermere faces a similar challenge. And Servettaz’s words still carry a warning: “Communities get the lakes they deserve.”
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Will Stoddart is a London-based health and science journalist. He writes regularly for the Daily Mail’s Good Health section and The Telegraph, and his work has also appeared in the Financial Times, The Times and The Guardian. He specializes in health, medicine and environmental stories.
