Love Windermere

1. Is there untreated sewage in Windermere?

Treated sewage waste (effluent) is discharged into rivers and streams that feed into the lake from United Utilities Waste Water Treatment Works in the main towns of Ambleside and Windermere, and a number of smaller treatment works (operated by United Utilities) around the wider catchment.

There is a permitted discharge of untreated but screened sewage for storm overflow into the lake at Glebe Road, Bowness-on-Windermere, and at Ambleside. These are regulated by the Environment Agency.

There are also private residential and commercial sites with their own treatment facilities. These range from basic septic tanks to ‘package plants’ that offer a higher quality of treatment. General binding rules establish how these discharges should be managed.

2. What is the National Park Authority doing to protect the lake?

We are part of the “Love Windermere” partnership - the biggest ever cooperation of sectors to tackle challenges in the lake. This evidence-led programme includes a range of actions from partners, which the National Park Authority is supporting, such as the Big Windermere Survey. The strategies set out in our 2020-2025 new Partnership Plan, the management plan for the Lake District, provide a context for this.

3. What are water companies doing to improve water quality in the lake?

United Utilities has worked to reduce phosphate concentrations in the final treated effluent from all of their sewage treatment works in the Windermere catchment, from 2mg per litre in 1990 to 0.25mg per litre in 2020. This reduction has come about from the most recent improvements at Ambleside Waste Water Treatment Works, Windermere Waste Water Treatment Works and at the Glebe Road pumping station. Between 2020 and 2025 United Utilities are investigating the impact on water quality of the storm sewage overflows from within the catchment to provide the evidence for future improvement schemes. Take a look at the United Utilities plans for Windermere.

Between 2020 and 2025 United Utilities is investigating the impact of the highest-spilling storm overflows throughout the North West region to provide the evidence for future improvement schemes. Read more about combined sewer overflows.

In April 2023, United Utilities announced a £19million investment in Windermere to help reduce storm water spills.

4. I’ve heard there is blue-green algae in the lake, is the water safe and clean enough to go in?

Algal blooms occur naturally in bodies of water, and some such as blue-green algae can be toxic to humans and lethal to animals. The algae area, or blooms, are usually in one part of the water and not all blooms are toxic. However, it's impossible to tell if the algae is the dangerous kind just by looking at it, so it's best not to enter the water if you suspect there is algae. Look out for local information next to the lake or check the Environment Agency’s map for reported algal blooms.

Read more about the current algal blooms (cyanobacteria) in this statement from the Freshwater Biological Association, UK Centre for Ecology and Hydrology and Lancaster University.

You can also use the Centre for Ecology and Hydrology’s ‘Bloomin Algae’ app to record and report any bloom you spot.

5. Can dogs go in the lake?

Yes, but be aware of localised occurrences of blue-green algae.

Read more in the answer above.

6. What’s the impact on fish and wildlife?

High nutrient concentrations (including phosphate in treated sewage effluent and from other sources such as applied fertilisers), can result in a process called eutrophication, leading to increased growth in naturally occurring algae. This can lower the concentration of dissolved oxygen available for fish, as well as smother spawning grounds and prevent light reaching aquatic plants changing the plant communities in the lake.

7. Are septic tanks causing problems?

There are approximately 1500 residential properties within the lake catchment that aren’t connected to the sewer network which use a septic tank or package treatment plant for sewage and waste water treatment. A number of larger sites, such as hotels, caravan parks and campsites, are also not connected to the sewer network. These sites have permits to discharge treated sewage effluent to watercourse or soakaway. The individual impact on water quality of each of the sites spread throughout the catchment is very low but the cumulative load can potentially be significant. In October 2022 the Environment Agency and Lake District Foundation launched a new campaign to support septic tank owners and help look after Windermere and the wider catchment. An information pack, Call of Nature, was sent to all properties in the catchment with help and advice. Find out more on the Call of Nature website.

Any new septic tank or non-mains drainage are subject to planning approval and the National Park Authority’s Local Plan. Applications for planning permission should be supported by a full assessment of the proposed use of septic tanks, to confirm that no adverse effects will arise from the installation. This assessment should focus on the likely effects on the environment, amenity and public health.