What Lies Beneath? Citizen scientists reveal more than half of UK waterways show signs of poor water quality
More than half of the UK’s waterways tested during a nationwide citizen science event showed signs of poor water quality. That’s the headline finding from Earthwatch’s Spring 2026 Great UK WaterBlitz report, which saw thousands of volunteers head to rivers, streams, ponds and lakes across the country to investigate what lies beneath the surface.
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Armed with simple testing kits, families, schoolchildren, community groups and volunteers collected data from more than 2,300 locations, helping to create one of the largest snapshots of freshwater health ever gathered by citizen scientists in the UK. The results reveal some serious concerns about the state of the nation’s waterways, but also some encouraging success stories.
Why does this matter?
Healthy rivers, lakes and streams support wildlife, provide drinking water and create places for people to enjoy nature. Yet pollution from farming, sewage systems and urban runoff often combines to create complex challenges for waterways. Rivers that have already been affected by agricultural pollution are increasingly being pushed closer to their limits by ageing and inadequate wastewater treatment infrastructure.
Understanding the full scale of the problem has been difficult because monitoring data is often incomplete or missing. Citizen science helps address this challenge by collecting valuable information from thousands of locations that may otherwise go untested.
A huge effort across the UK
Together, our volunteers generated a powerful national snapshot of water quality over a single weekend. The findings highlight significant water quality challenges across the UK:
- 4,677 citizen scientists took part, including nearly 1,000 children.
- Volunteers surveyed 2,315 locations across the UK.
- Participants measured nitrate and phosphate concentrations as indicators of water quality.
- 57% of all measurements recorded nutrient concentrations at levels considered unacceptable, indicating poor water quality.
- pH levels were also recorded as part of ongoing work to better understand phosphate concentrations against UK site-specific thresholds.
- More than 6,000 Key Stage 2 pupils and their teachers joined a FreshWater Watch Live Lesson webinar delivered by the Earthwatch education team.
Wales leads the way
Wales achieved its best-ever Great WaterBlitz result. Only 18% of Welsh sites recorded ‘unacceptable’ water quality, making Wales the best-performing nation in the UK during the April 2026 event.
Several areas in Wales also achieved perfect scores, with every survey in the area showing ‘acceptable’ water quality. These included the county of Powys and West Glamorgan, as well as the Welsh Severn Uplands sub-basin within the cross-border Severn River Basin District.
England continues to face major challenges
England recorded the poorest water quality of any UK nation for the latest WaterBlitz, continuing a pattern seen in every Great UK WaterBlitz to date. In April 2026, 61% of English sites recorded unacceptable nutrient concentrations. The Anglian River Basin District had the worst result in the UK, with 78% of measurements showing unacceptable water quality. At county level, Bristol and Rutland recorded the poorest results, with every measurement indicating unacceptable water quality.
Areas showing excellent water quality
Some parts of the UK demonstrated that healthy waterways are possible. The Lune and Kent & Leven river basins in Northwest England recorded 100% acceptable water quality across all surveys. The Welsh Severn Uplands river basin achieved the same result.
What is the Great UK WaterBlitz?
FreshWater Watch is the UK’s largest citizen science water quality project. It was created to help uncover problems that cannot always be seen with the naked eye. A river may look clean and healthy on the surface, but harmful pollutants can still be present in the water. The Great UK WaterBlitz is a nationwide citizen science event run twice a year by Earthwatch Europe through its FreshWater Watch programme.
Using specially designed testing kits, volunteers are trained to measure nutrients such as nitrate and phosphate. These substances can indicate pollution from sources including sewage discharge, agricultural runoff and urban wastewater. Participants record their findings using a standardised method, creating robust scientific data that helps build a clearer picture of water quality across the country and helps to fill important gaps in our understanding of freshwater health.
What next? Turning data into action.
The nutrients measured during the WaterBlitz indicate water quality and can also signal the presence of other chemical and biological pollutants. Through FreshWater Watch, Earthwatch enables communities to collect reliable local data that complements official monitoring programmes and shows the areas that require action.
The Spring 2026 Great UK WaterBlitz demonstrates the power of citizen science to uncover environmental issues that might otherwise go unnoticed. By collecting thousands of measurements in just one weekend, volunteers have helped build a clearer picture of freshwater health across the UK. But the findings also show that data alone is not enough. Earthwatch Europe is calling on national and local authorities to work with communities, strengthen freshwater monitoring and tackle the sources of pollution affecting rivers and streams.
