A Beginners Guide to Gathering Data and Testing the Waters
You don't need to be a scientist to test your local river. Across the country, ordinary people are gathering the evidence that is holding water companies to account. This guide will help you get started.
Why does it matter?
- Water companies are allowed to monitor and report on themselves. Citizen testing is the independent check they cannot control.
- Your data can be used as evidence, shared with your MP, shared with the Environmental Agency, water company and used for media outreach.
- Local stories change minds faster than national statistics.
1. Before you go, a few minutes of preparation makes your testing far more useful. Check these things first:
Find out what is upstream
• Which water company operates the sewage works near you — and what is their discharge record?
• Check Sewage Map. The water company data goes into the Sewage Map. Sewage Map shows you trends and history.
• Is there already a local river group? Join them - don't reinvent the wheel
Stay safe!
• Always wear gloves. Wash your hands thoroughly afterwards.
• Don't go alone to remote stretches.
• Never touch water near an outflow pipe.
• Cover any cuts or broken skin.
• After heavy rain, overflow risk is highest - wait 48 hours if you plan to get in the water yourself.
• If the river is in spate/ very high do not sample – it can be dangerous.
2. What to Look For - Even Without a Kit!
Your eyes and nose are your first instruments and observation is powerful. Before you do anything else, record what you observe:
• Foam or froth on the surface - a common sign of sewage
• Unusual colour - grey, brown, green or milky water
• Smell - sewage, chemicals or anything unusual
• Dead or distressed fish - report immediately
• Sewage fungus - grey slime on rocks and the riverbed
• Algal blooms - green or blue-green covering on the surface
• Visible outflows - pipes discharging into the river
• Absence of wildlife - very few insects, birds or fish
• Oily film on water on water or boats
Photograph everything with time, date and location switched on in your camera settings.
3. What You Can Test For
Simple, affordable tests can reveal a great deal. You don't need a laboratory.
Phosphates and Nitrates - Fresh Water Watch
One of the most accessible ways to start testing is through Earthwatch's FreshWater Watch programme. By registering as an individual member at freshwaterwatch.org/pages/individuals, you get access to online training, a methodology guide, data tools and enough water testing kits to cover a year of monitoring which are all included in the membership cost.
The kits use small colour-change tubes to measure nitrate and phosphate levels. You add a small water sample, wait a few minutes, and compare the resulting colour against a chart. The darker the colour, the higher the level of pollution. Your results feed directly into an open-access national map in real-time, with instant feedback explaining what your findings mean.
Earthwatch also run the Great UK WaterBlitz twice a year. The next one is 24th – 27th April 2026, testing nitrate, phosphate and pH. Over 6,000 people took part in September 2025 and 60% of sites showed poor ecological health. In the Thames river basin 81% of measurements showed unacceptably high levels of nutrient pollution. Sign up at earthwatch.org.uk/greatukwaterblitz April is now full although space remains in September.
Important note: kits are only available to registered FreshWater Watch members and cannot be bought separately. Register first, then the kits are provided as part of your membership.
Dissolved oxygen
Low levels signal sewage pollution and kill fish. A healthy river has high dissolved oxygen. Basic handheld meters are available from around £15-£30. Hanna
pH
Indicates chemical pollution. Most healthy rivers sit between 6.5 and 8.5. Simple test strips or a basic meter will do. Hanna Amazon
Temperature
Warmer water holds less oxygen. Rising temperature is a sign of environmental stress. A basic thermometer is all you need.
E. coli and coliform bacteria
The key indicator of sewage contamination — this is what makes people ill. You will need a Water Rangers e-coli kit
Turbidity Sechi Tube
River Flow local to you
4. Recording Your Results
One result is interesting. A pattern over time is evidence. Always record the following:
- Date and time
- Exact location - GPS coordinates or a what3words address
- Recent weather and rainfall
- Water appearance, smell and any visible signs
- Your test results with units
- Photographs with location data switched on
Free tools to record and share:
- A shared Google Sheet with your group
- The Sewage Campaign Network shared google drive
- The Riverfly Partnership app
5. If You Find Something Wrong
Report it immediately - don't wait!
• Environment Agency pollution hotline: 0800 807060 - free, 24 hours, 7 days a week
• Keep the reference number they give you*
• Take additional photographs and samples if you can do so safely
• Note the exact time and location — this matters for any legal action
• Report to your water company via their website
• Contact your local river group and the Sewage campaign network
• Notify your MP, especially if you have repeat evidence of pollution
• Talk to your local press – often open to stories around sewage
Please note! - don't post unverified results on social media before you understand what they mean. Document everything privately first then share through the campaign network, who can help you interpret and amplify your findings.
6. Going Further
Once you have started, there is a whole world of citizen science to explore:
Bathing water status: Applying for official bathing water designation for your river forces the water company to monitor and publish data. It has transformed rivers like the Wharfe at Ilkley and the Ouse at York - your river could be next
Join the network: The Sewage Campaign Network connects river groups across the country. Your data is more powerful as part of a national picture
Further testing: Heavy metals, forever chemicals (PFAS) and pharmaceuticals need laboratory analysis - but you can collect and send samples.
You can consider working with the polluter – they may offer funding for testing. They often have a community fund
Writing to the water company with an Environmental Information Request (EIR). Could request data, a visit, history of permits and licences for the sewage works etc – helps you to build up a deeper knowledge of your river.
Riverfly monitoring: A standardised survey of the tiny invertebrates living in river sediment — one of the best long-term health indicators available. Free training through the Riverfly Partnership at riverflies.org
Useful Contacts and Resources
- Environment Agency pollution hotline: 0800 807060 (free, 24 hours)
- Surfers Against Sewage sewage map and Citizen Science Toolkit
- Top of the Poops live sewage data: top-of-the-poops.org
- Riverfly Partnership training: riverflies.org
- The Rivers Trust Sewage Map – has other industries as well as sewage and can find out about the specific permits
- Earthwatch testing kits
- Windrush Against Sewage
Some citizen science groups and action to inspire you
HoTWater, Henley
Windsor River Watch
Anglers Against Pollution Water Quality Monitoring Network
Ilkley River Group