Image description: The Tower Bridge as seen from City Hall on the South Bank, with the Thames flowing beneath it. Photo by Call Me Fred on Unsplash

Environmental Charity Earthwatch Europe has just published the results from our Great UK Waterblitz, a biannual campaign calling on citizens to go out and test the quality of their local freshwater including rivers, streams and lakes.

Between 19-22 September 2025, 5,708 citizen scientists surveyed 3,430 freshwater sites; creating a citizen-led snapshot of water quality across the UK. Of the surveys, 2,856 were collected in England; 200 were collected in Scotland; 208 measurements were taken in Wales; and 166 datapoints were gathered in Northern Ireland.

Results in brief:

• 60% of datapoints across the UK show poor water quality, with unacceptable levels of nutrient pollution.
• England consistently has the worst water quality in the UK, as tracked over four WaterBlitz events.; this Autumn 66% of sites tested had unacceptable levels of nutrient pollution.
• The data suggests the Thames river basin district has the worst water quality in the UK, with 81% of measurements showing unacceptable levels of nutrient pollution; despite the Thames Tideway Tunnel becoming fully operational in February of this year
• 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 have the best water quality, with 100% of measurements indicating low levels of pollution
• In England, the county of Northumberland has the best water quality, with 94% of measurements indicating good ecological status
• Cambridgeshire has the worst water quality in the UK, with 91% of measurements indicating poor ecological status