More than 50bn litres of effluent from sewage treatment plants in the Lake District have flowed into Windermere and the rivers and smaller lakes which surround it since 2017, new figures have revealed.
Flow monitor data released by United Utilities show the levels of treated sewage from six wastewater treatment works into the catchment of England’s biggest freshwater lake. Environmental campaigners say the discharges have fuelled growth of potentially toxic algae which can kill fish and other algae.
The data disclosed to the Oxfordshire campaign group Windrush Against Sewage Pollution reveals just one plant, Windermere wastewater treatment works, has discharged up to 30m litres of treated effluent a day into the lake, equivalent to 12 Olympic-sized swimming pools.
Matt Staniek, founder of the campaign group Save Windermere, said: “It’s absolutely abhorrent that Windermere is being used as a dumping ground for wastewater and sewage. Sewage, both treated and untreated, is the primary driver of the algae growth threatening Windermere’s fragile ecology.”
The Observer previously reported on the discharges into Windermere from illegal spills at plants in the catchment. Sewage plants and pumping stations were revealed to have spilled on 501 days from 2018 to 2023, including a pumping station estimated to have pumped 140m litres of waste into Windermere.
A project, Only Rainwater into Windermere, will publish a study next year with the ambition of protecting the ecology of the lake. The project will study infrastructure schemes at Lake Annecy in France and Lake Washington in the US, which were both transformed with sewage diversion schemes.
The cost of any scheme may run into billions of pounds. A feasibility study by United Utilities in February last year examined the option of piping sewage and wastewater more than 40 miles to Grange-over-Sands on the north side of Morecambe Bay in Cumbria, with an estimated cost of £3.5bn to £6.4bn.
Edward Twiddy, independent convenor of Only Rainwater into Windermere, said the project was a unique opportunity to improve one of the one of the most important destination sites in the UK, but no decision had been made on financing.
He said the study would aim to show the economic benefits of protecting Windermere. He said: “I hope it will demonstrate that this will be good value for money not just for the ecology and economy of Windermere but for the economy of the north-west and the economy of the UK.”
United Utilities is investing £200m by 2030 to upgrade wastewater treatment works at Windermere and reduce the spills from all storm overflows. It says it has already invested tens of millions of pounds over the psst two decades upgrading wastewater treatment plants, with the amount of phosphorus entering the lake from its assets halving since 2015. The Environment Agency says phosphorus and nitrate levels in the lake have been declining, but higher temperatures can lead to more algae blooms.
A spokesperson for United Utilities said: “Over the next five years, we’re delivering the largest investment in wastewater infrastructure for a century in Windermere, something that campaigners and customers alike have told us they want to see.
“We’re excited to be part of the coalition and funding a study that will explore how to protect the lake for generations to come from the challenges that climate change and population growth will bring.”
Photograph by Christopher Furlong/Getty Images