Harmful bacteria 'highest in summer' in Windermere

Campaigners are demanding action to address "poor" water quality results

Water quality testing in Windermere has found harmful levels of illness-causing bacteria throughout the summer months at England's largest lake.

Analysis found high levels of Escherichia coli (E.coli) and Intestinal Enterococci (IE), indicating sewage pollution, at the time when the lake is busiest for swimming and watersports.

The Big Windermere Survey (BWS) saw 350 citizen scientists collect more than 1,000 samples over two and a half years at more than 100 locations - many of which had never been tested before.

Campaigners want "decisive action" to improve the lake. The Department for Environment, Food and Rural Affairs (Defra) has committed to getting water quality back to normal.

It said there was "a lot of damage to undo".

The Freshwater Biological Association (FBA), which co-ordinated the citizen science project with the University of Lancaster, said the elevated concentrations of E.coli and IE in summer were "particularly concerning as they indicate an increased risk of gastro-intestinal illness if water is ingested".

Simon Johnson, the FBA's executive director, said: "When you see a place you love so much, that is so important, when the water quality of that place is below what I think society expects and demands, then that's really concerning."

He said Windermere was one of the world's most famous lakes and if the issues could not be solved there, it did not bode well for the future of other equally important but less famous sites in the Lake District.

"Its scientific, ecological, cultural importance, whether you are an artist, a poet, wild swimmer, motorboat owner, it's just intertwined in the whole kind of social and ecological fabric of the Lake District," he added.

"If we can't get this right on Windermere, where are we going to do it?"

The findings show much of the lake's shoreline in the north-west, north-east and south-west areas in summer were only consistent with standards for "poor" bathing water quality.

But the data shows overall Windermere's levels of bacteria have a "good" water quality rating through spring, autumn and winter.

The lake is a popular hotspot for watersports and the Great North Swim

Tests for phosphorus - a pollutant that causes algal blooms and damage to aquatic wildlife and comes from sources such as wastewater and fertiliser run-off from agriculture - revealed levels of the chemical that exceed expected standards.

The FBA warned that rare and threatened species in the lake such as Arctic char would face a "steady and devastating decline" without action to clean up the water.

The report also reveals some of the 71 sample sites tested had consistently demonstrated high concentrations of both phosphorus and at least one of the bacteria.

These include Waterhead, Millerground, Bowness Bay, Belle Isle, Mitchell Wyke Bay, south-west shore sites and near the River Leven outflow on the lake, and river locations on the Rothay, Stock Ghyll, Black Beck, Mill Beck, and Wilfin Beck.

Windermere, part of the Lake District National Park Unesco World Heritage Site, is home to more than 14,000 people, and its scenery, rare species and cultural heritage attract seven million visitors a year, generating £750m for the local economy.

But it has been the focus of concerns over pollution, from sources including wastewater from United Utilities and private sewage treatment and rural and urban land use, with the government pledging to "clean up Windermere" from the high levels of pollutants it faces.

The volunteer testing, which took place from June 2022 to November 2024 across 10 sessions, aimed to address concerns about water quality and fill in gaps in traditional monitoring.

The Environment Agency monitors water quality through the summer months at four sites as part of its bathing water assessments, with all receiving "excellent" ratings in the last annual classification.

The FBA is calling for the pollution hotspots identified by the testing to be investigated, and for the Environment Agency to increase the number of bathing water sites and monitor them through the year.

A Defra spokesperson said: "This government shares the nation's fury at unacceptable levels of pollution pumped into this national treasure.

"We have committed to ending sewage pollution into Windermere entirely, boosted monitoring of sewage spills nationwide and are increasing enforcement to hold polluting companies to account.

"We know that there is a lot of damage to undo, but we are getting on with the work to ensure that the British people will be able to see genuine results."

Additional reporting by PA Media