Scientists have published the results of the biggest ever citizen science survey examining the water quality of Windermere – England’s largest natural lake.

Data from water samples gathered as part of the ‘Love Your Lake: Big Windermere Survey’, led by scientists from Lancaster University and the Freshwater Biological Association, represent the start of what is planned to be a long-term monitoring programme. This will build a detailed and geographically widespread picture of water quality in one of the Lake District’s most important catchments.

The independently analysed survey data will be freely available to all from today, Wednesday 28^th September, including the Love Windermere Partnership which aims to develop evidence-based, long term plans to improve the water quality of Windermere.

Dr Ben Surridge, Senior Lecturer at Lancaster University and a lead investigator for the survey, said: “High-profile concerns have been raised about the condition of Windermere, in particular because of cyanobacterial blooms and bacterial pollution. The Big Windermere Survey is a large-scale citizen science project, bringing together people from across the community and giving them an opportunity to actively participate in finding out more about the lake that they care so much about.

“The survey is the most spatially-intensive snapshot of Windermere’s water quality to date. Compared to the small number of locations included in regular monitoring work on Windermere, this provides an unparalleled picture of the water quality within the lake and its catchment.

“Thanks to fantastic support from our volunteers, data from this first survey now provide the basis to build a scientifically robust dataset across the catchment. As this dataset grows over time, it will be used to identify areas of concern within the catchment and provide the evidence required to address sources of water pollution.”

Dr Louise Lavictoire of the Freshwater Biological Association and another lead investigator said: “The survey is not intended to be an isolated event and our ambition is that this will be the first of an ongoing series of quarterly sampling events on Windermere and its catchment. These first results provide one data point in time and we should always use caution to draw conclusions from single data points. Repeated surveys will extend these first results and create a scientifically robust picture of how water quality varies across the catchment.”

Scientists behind the Big Windermere Survey recruited a team of around 100 dedicated volunteers who collected water samples from 93 sites across the Leven catchment on 26^th June 2022. This catchment contains iconic Lake District bodies of water, including Windermere, Grasmere, Rydal Water, Blelham Tarn and Esthwaite Water, alongside a number of rivers and streams flowing into Windermere.

The samples gathered by the volunteers were analysed for a range of nutrients and for bacteria within research laboratories at Lancaster University and at externally-accredited laboratories.

Whilst the survey’s results provide the most intensive ever snapshot of water quality across the catchment, the scientists stress that care needs to be taken when comparing the results from one day of sampling to water quality standards. Long-term data are required to officially classify the status of water bodies against standards, in order to account for changes in water quality through time such as across seasons or with variable weather conditions. Future surveys will establish a longer-term picture of water quality in the catchment, providing a robust basis for classifying water bodies against standards.

However, water quality standards can be used to provide context for the results of the first survey. The scientists used inland bathing water standards from the European Union Bathing Water Directive to compare to levels of bacteria in the samples. Bacteria such as E. coli and intestinal enterococci are indicators of potential contamination of water by faecal material, either from humans or from animals. The results show that for bacteria on the day of the survey:

• 90% of all sites within the catchment met standards for ‘Good’ or ‘Excellent’ bathing water quality, meaning that these sites had low levels of E. coli and intestinal enterococci.
• For the 59 samples taken from Windermere shoreline sites, 92% met standards for ‘Excellent’ or ‘Good’ bathing water quality.
• There are four locations on Windermere that are officially designated as bathing waters under the Bathing Water Directive. Three of the four sites (Lakeside YMCA, Millerground Landing and Rayrigg Meadow) met standards for ‘Good’ or ‘Excellent’ bathing water quality.
• At the fourth designated site, Fellfoot, levels of E. coli were higher than the standard required for ‘Good’ bathing water quality. However, as a designated bathing water, levels of bacteria at Fellfoot are monitored regularly by the Environment Agency and the results are openly available to the public online. Based on these data, the quality of the bathing water at Fellfoot is generally excellent. Further, two additional samples from Fellfoot, collected immediately to the north of the designated bathing water sampling site, did not show elevated levels of E. coli on the day of the survey.

The scientists were also interested in the concentrations of key nutrients such as phosphorus. Alongside factors such as increasing water temperature, increases in the concentration of phosphorus can contribute to phenomena such as cyanobacterial blooms, also known as blue-green algal blooms. The samples were compared to nutrient standards from the European Union Water Framework Directive. The results show that for phosphorus on the day of the survey:

• Of the 67 samples taken from six lakes across the catchment, 52% met standards for at least ‘Good’ status, containing relatively low concentrations of phosphorus.
• For Windermere itself, 58% of the 59 samples taken from its shoreline met the standards for at least ‘Good’ status based on phosphorus concentrations.
• Hotspots of higher phosphorus concentration on Windermere’s shoreline were identified around Waterhead, Millerground, and east and west lake shores around Crow Holme and in the area between Storrs and Tower Wood.
• Of the river sites sampled in the survey, 24 out of 25 met the standards for ‘High’ or ‘Good’ phosphorus status.
• One river sample, taken from the River Brathay at Skelwith Bridge, contained a slightly elevated phosphorus concentration, which met the standards for ‘Moderate’ status under the Water Framework Directive.

Samples were also analysed for nitrate and for total ammonia, two forms of nitrogen which is another important nutrient in water. Nitrate concentrations were relatively low across all sample sites, significantly below the standard required for drinking water. Concentrations of total ammonia, which includes a form of nitrogen that is toxic for organisms such as fish, were also found to be low across the samples.

The study’s scientists say that potential pollutants such as phosphorus and bacteria can enter Windermere from multiple sources. These include final effluent from wastewater treatment works, sewer overflows, septic tanks, diffuse pollution from land and release from sediments at the lake bed. Results from this first survey already highlight priority areas within the catchment where further work can now be undertaken to identify and reduce significant sources of pollution.

Dr Surridge said: “The survey emphasises that it is a mistake to think about Windermere as a single body of water with the same water quality at all locations. The results show that water quality is not high in all areas of the lake, but equally there is no evidence in the survey of poor water quality across the whole of Windermere. Understanding where there are areas of poorer water quality in Windermere is absolutely essential, if we are to identify what is causing declines in water quality and address these issues successfully.”

The full dataset from the Big Windermere Survey is openly available to the public on Cartographer via the Freshwater Biological Association website (https://www.fba.org.uk/volunteer/the-big-windermere-survey). The results are displayed on an interactive map showing the locations where samples were taken. The Big Windermere Survey scientists have also produced summary maps showing key data and a briefing note to help understand the findings, available via the same website.

The project received generous funding from Lancaster University’s Vice-Chancellor’s Prize for Participatory Research (2021-2022) and from United Utilities. The survey is also supported by the UK Centre for Ecology and Hydrology, Lake District National Park Authority, South Cumbria Rivers Trust, Brathay Trust, National Trust and the Environment Agency.