Freshwater data for positive change
Our natural freshwater habitats in the UK are suffering and we need urgent action.
The Great UK WaterBlitz is a biannual campaign calling on everyone to go outside and test the quality of their local freshwater bodies, including all rivers, streams, lakes, ponds, canals and wetlands. This vital data helps to build a clearer picture of water quality across the UK. The Great UK WaterBlitz is part of our ongoing FreshWater Watch citizen science monitoring project.
Great UK WaterBlitz Report
During 19-22 September 2025, nearly 6,000 citizen scientists uploaded 3,430 datapoints from freshwater bodies across the UK.
We found that:
- Overall, 60% of datapoints across the UK showed poor water quality, with unacceptably high levels of nutrient pollution
- The Thames river basin district had the worst water quality in the UK, with 81% of measurements showing unacceptably high levels of nutrient pollution
- The counties of Tyrone in Northern Ireland, Mid Glamorgan in Wales, and the four counties of Argyll and Bute, Ayrshire and Arran, City of Aberdeen and Dunbartonshire in Scotland had the best water quality, with 100% of measurements indicating low levels of nutrient pollution
- In England, the county of Northumberland had the best water quality, with 94% of measurements indicating good ecological status
- Cambridgeshire had the worst water quality in the UK, with 91% of measurements indicating poor ecological status
You can explore the results further in the Great UK WaterBlitz Autumn 2025 report:
Be the first to know about Great UK WaterBlitz events in 2026!
We will be running the next data collection event between 24-27 April. If you would like to find out more about this event and how you can take part, please express your interest below. We will then let you know as soon as registrations open.
About FreshWater Watch
FreshWater Watch is the largest citizen science water quality project in the UK. FreshWater Watch trains individuals and communities to use our simple water monitoring toolkit to detect nutrient pollution. It is not always possible to determine water quality at first glance. The FreshWater Watch toolkit helps to uncover the secrets hidden underneath the surface, making the invisible, visible. With this robust data we can create real change.
Thank you to our funders and supporters!
Funders
- CaSTCo
- Chapman Charitable Trust
- Esme Mitchell Trust
- Royal Society of Chemistry
Supporters
Support the Great UK WaterBlitz
It costs £6 for each water testing kit used in the Great UK WaterBlitz and we rely on voluntary donations to support our work. Every donation means that we can test more waterbodies in more locations across the UK. Please donate to make the Great UK WaterBlitz as big as possible – the more data, the louder the call for change.
£6 can cover the cost of your water testing kit
£12 can pay for your kit and pays it forward for someone else
£24 can help us boost our campaign and makes you a freshwater hero
FAQs
Who can take part in the Great UK WaterBlitz?
Anyone who wants to help fight for better freshwater quality can take part in the Great UK WaterBlitz. You must be available to go outside and spend 20 minutes over the weekend of the 24-27 April testing a freshwater river, stream, lake, pond, canal or wetland.
Do I need to use an app?
No, the app is optional. You can upload results through an online form if you have a strong internet connection outside from a mobile device. Alternatively, you can print a paper datasheet to record handwritten results and upload them later from home.
How long will the testing take?
You will be outside for about 20 minutes in total.
What will I be measuring?
You will be measuring two key nutrients, nitrate and phosphate, and also the pH of your chosen waterbody. Alongside the tests, you will be recording some simple visual observations, such as land use and any presence of algae.
Why are nitrate and phosphate levels important?
Nitrates and phosphates occur naturally in the environment and are essential for plant growth. Healthy freshwater ecosystems usually have small amounts of these two nutrients. However, human activity on land can cause unnaturally high levels of nutrients to enter waterbodies.
These nutrients are commonly present in domestic and industrial waste and sewage, as well as in the fertilisers that wash off farmland.
High levels of nutrients trigger a process called eutrophication, in which excessive plant and algal growth leads to high levels of bacteria. These bacteria then decrease oxygen levels in the water, harming aquatic plants and animals.
Where can I test?
You can test any freshwater body (rivers, streams, lakes, ponds, canals and wetlands), anywhere in the UK. Freshwater that is downstream of a sewage treatment works or an outfall pipe is more likely to have higher nutrient levels than freshwater that is upstream.
Before you do your test, make sure it’s safe to do so – we advise staying several metres away from potential pollution sources for your own health and safety – and that you have permission to be on the land (if it is private property).
Do I have to live near a river to take part?
No, but you do need to be able to visit a freshwater body (river, stream, lake, pond, canal or wetland) to use your test kit between 24-27 April.
Do I need to have done water quality testing before?
No, the testing kits are easy to use and you don’t need any prior experience to take part in the Great UK WaterBlitz.
Where will my results appear?
After uploading your results through the app or online form, you will be able to view your datapoint on the Great UK WaterBlitz results map. Please allow up to an hour for any new datapoints to appear between 24-27 April.
Why is the data important?
Freshwater bodies are suffering from pollution from a number of sources – sewage, nutrients and chemicals. To change attitudes and policy towards rivers, streams, lakes, ponds, canals and wetlands, we need robust data on water quality.
Citizen science activities like the Great UK WaterBlitz and ongoing monitoring via the FreshWater Watch project are vital to provide a robust, data-driven picture of the health of our freshwater bodies.
How will you use the data?
The data you submit as part of the Great UK WaterBlitz will be analysed and compiled into a public report, which will be published in May. The analysis in this report will be used to create a snapshot of freshwater health across the UK.
We will use this data to challenge water companies on their action, provide the Environment Agency with information on waterbodies that they do not monitor, and to inform the Office for Environmental Protection on any activities that we suspect are illegal.
What individual actions can I take to improve the health of our freshwater bodies?
Ensure that you dispose of waste products appropriately. Never flush wet wipes down the loo, or pour fats, oils and grease down the sink. Try to use natural cleaning products, rather than harsh chemicals. Remember, if it goes down the sink, it ends up in your drink.
How can I partner with you on research projects?
Earthwatch Europe is an Independent Research Organisation and we welcome conversations with academic partners. If you’d like to partner with us on the Great UK WaterBlitz or other freshwater citizen science projects, please contact water@earthwatch.org.uk.