THERE has been a 76 per cent drop in the population of a riverfly species below a sewage outlet near Windermere compared to above the pipe, new figures show. 

Campaign group Save Windermere released data conducted with Wild Fish on invertebrate species populations above and below sewage outlets in the Windermere catchment. 

The figures show an average 76 per cent reduction of pollution-sensitive river fly species on Cunsey Beck below Near Sawrey wastewater treatment works.

BBC Panorama recently made a documentary on a large fish kill that occurred near the Near Sawrey outlet pipe in June 2022 which the Environment Agency said was 'likely to be due to high levels of algae' but did not determine a single cause. 

The figures also revealed an average 75 per cent reduction in the species on Wilfin Beck below Far Sawrey works, and a 64 per cent reduction on the River Rothay below the storm overflow pipe for Ambleside treatment works. 

READ MORE: Environment Agency will not reopen Cunsey Beck investigation

The report states: "The number of invertebrates below United Utilities' assets on these rivers were found to be as low as two individuals compared with hundreds upstream of the works.

"The first year of Windermere results are very concerning and provide solid evidence for WildFish and Save Windermere to continue lobbying United Utilities and the Environment Agency to ensure urgent action is taken to stop sewage, treated and untreated, degrading the Windermere catchment." 

The data collection and analysis involved a citizen science project which was conducted during the spring and autumn of 2023 and was led by Dr Nick Everall and Dr Sam Green. 

The invertebrate samplings are used as a means to determine the overall ecological health of the area which would include larger fish and bird species, the group argues. 

A United Utilities spokesperson said: “Near Sawrey and Far Sawrey treatment plants are small sites servicing a combined population of 370 people, which is around 2 per cent of the Windermere catchment. Both plants and the one at Ambleside operate in line with their environmental permits.

"We have started work on a further £41 million investment programme at our sites around Windermere and are working with others to address all sources of lake pollution including private sewage systems, highways runoff and pollution from land.”