Why Windermere Matters: England’s Largest Lake, the Heart of the Lake District, Sewage Pollution and the Campaign to Save It
Windermere is England's largest freshwater lake, often referred to as the ‘jewel in the crown’ of the Lake District National Park. It is the most southerly of the major lakes, and like many of the others, it is narrow, ribbon-shaped, and deep. Formed 13,000 years ago during the last ice age, Windermere spans 10.5 miles in length, one mile at its widest point, and reaches a depth of 64 metres at its deepest part.
Windermere holds significant national and international importance due to the rare and protected species it supports, such as the Atlantic salmon, Arctic charr and European river eel. It also has remarkable cultural significance, being part of a catchment that was home to iconic figures like Beatrix Potter, William Wordsworth and Heaton Cooper. Furthermore, Windermere serves as a thriving hub for the National Park's tourism industry, contributing approximately £750 million to the local economy annually.
In recent years, growing concerns have emerged about Windermere's water quality. The most notable and prominent of these voices is the Save Windermere campaign, which has been at the forefront of raising awareness about sewage pollution in the lake. The campaign is actively working to expose the failings of both regulators and the water company, United Utilities, regarding activities that threaten Windermere's ecological health.
The primary concern for Windermere's sustainability is its vulnerability to climate change, particularly evident in the extensive algal growth that can occur in the lake due to inadequate investment and lake management. Algal blooms can smother and even kill aquatic life and pose health risks to those engaging in recreational activities on the lake. Sewage discharges remain the primary source of nutrients fueling this algal growth. The severity of these blooms is further influenced by climatic conditions and nutrient input levels.
Between June 2022 and November 2024, the Big Windermere Survey, led by the Freshwater Biological Association, has undertaken water-quality monitoring in Windermere. Sampling at more than a hundred shoreline and inflow sites across all seasons revealed widespread bacterial contamination, with many popular swimming areas recording faecal indicator bacteria levels exceeding recognised bathing-water thresholds, especially in summer. Phosphorus concentrations were also elevated in several basins, underlining the scale of nutrient enrichment. These results show that the regulatory monitoring network, which covers only a handful of locations, significantly underestimates the extent of pollution.
Although phosphorus concentrations peaked in the 1990s, the lake is still showing concerning symptoms, with dissolved oxygen levels in the lake's deep waters continuing to decline and algal biomass persisting, with notable increases in the lake's north basin.
Recent research conducted by the campaign, in partnership with Map Impact and backed by the UK Space Agency, has demonstrated a direct correlation between visitor numbers and algal spikes in Windermere. They found that algal growth is also exacerbated during prolonged warm, dry weather periods. Interestingly, the study found no correlation between agricultural input and algal spikes, likely due to the specific type of farming and land use in the catchment area. However, further investigation into the contribution of United Utilities' infrastructure was hindered by the company’s lack of transparency.
While there is a clear relationship between human activity and algal growth, the campaign encourages everyone to visit Windermere to experience its incredible natural beauty and support local businesses. The issue lies with inadequate investment to accommodate the area's growing popularity and the lack of attention given to lake management, which for Windermere requires a unique approach, as seen at iconic and sensitive lakes elsewhere in the world.
Despite the challenges posed by algal blooms and sewage discharges, Windermere remains open for recreational use, with a low likelihood of health issues from water interaction. Visitors are advised to check sewage discharge maps to see when discharges last occurred and to familiarise themselves with the signs of blue-green algae in the water as these pose a direct risk to human health.
To combat this existential threat, Save Windermere is calling for an end to all sewage discharges into the lake’s catchment. Inspired by the success of Lake Annecy in France—where sewage was redirected to achieve a sewage-free lake—the campaign highlights this as a proven solution. Working alongside local communities, businesses, and environmental groups, the campaign continues to raise awareness and lobby policymakers to "Save Windermere."
The campaign advocates for a sustainable, long-term solution to restore the lake and ensure its protection for future generations and local business. Their efforts highlight the urgency of safeguarding Windermere as a vital natural and cultural resource.
