Windermere water quality FAQs

Updated: 15 December 2021

We are aware of recent concerns regarding water quality in Windermere. There are a number of factors to address here, and we’re continuing to work with partners, including the Environment Agency and United Utilities. The strategies set out in our Partnership Plan provide a context for this and the information below answers some of the recent questions.

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 aware of the lake water quality in Windermere and are working with partners, including the Environment Agency, United Utilities and local stakeholders, to develop local actions to address this. 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.

4. I’ve seen the 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.

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.

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.

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.

8. Does farming and agriculture run-off affect the water quality?

Monitoring by the Environment Agency hasn’t highlighted any significant hotspots from agricultural pollution. However, studies in the catchment show that agriculture does contribute to phosphate levels in Windermere impacting upon water quality. The Environment Agency offers advice and guidance on best farming practice, preventing pollution and is working with farmers to reduce the impact of their land management on water quality. The Farming for Water Rules require good farming practice to avoid water pollution and benefit farm businesses.

9. What can I do to help?

There are many things which residents and users around the lakes can do to reduce the persistence of algal blooms in lakes, including:

  • Checking the condition and regularly emptying septic tank systems
  • Regular checking and emptying of holding tanks on boats to prevent pollution
  • Using phosphate-free cleaning products
  • Reducing fertiliser on lawns, gardens and farmland that can ultimately end up in the lake – and pay attention to the forecast – don’t spread if it’s going to rain.
  • Support your local Rivers Trusts and wildlife groups.