Swimming in UK Rivers: Spotting pollution and staying safe

This is a guest blog written by Matthew Woodard, Marketing & Campaigns Officer at The Rivers Trust.

Before you go, know the different types of pollution

Sewage is the pollutant we hear about the most and a major concern is the release of untreated waste from storm overflows during heavy rainfall. These overflows, designed to prevent drainage systems from flooding, can discharge raw sewage directly into rivers. Even our treated sewage is a problem, as the treatment processes don’t always eliminate harmful bacteria, chemicals, or microplastics, contributing to ongoing pollution.

Chemical pollution can take many forms, be tricky to spot, and originates from a plethora of sources, including industrial waste, agricultural and road runoff, and even the ordinary household products that go down our drains. Many of the chemicals in our rivers are not only harmful to wildlife but are remarkably persistent, with PFAS, commonly known as ‘forever chemicals’, taking over 1,000 years to break down.

Nutrient pollution often comes from agricultural activities, when fertilisers high in nitrates and phosphates are washed into our waterways. This can fuel algal blooms, which create large areas of low oxygen, significantly impacting aquatic wildlife and encouraging the growth of bacteria.

Plastic is an ever-present issue in UK rivers, with discarded bottles, packaging, wipes and microplastics making their way into the water. Large plastic waste poses an immediate hazard to wildlife, while microplastics, broken down from larger debris, are ingested by fish and enter the food chain, affecting entire ecosystems.

At the riverbank, know how to spot the signs

• Murky or foamy water: Unusual discolouration, cloudiness, or surface scum can all indicate the presence of pollution.
• Unpleasant odours: A strong sewage small suggests a recent or ongoing wastewater discharge.
• Algal blooms: These are easy to spot, look for large patches of green on the surface.
• Visible litter: Obvious signs of plastic waste or other rubbish often signal poor water quality.
• Recent heavy rainfall: Storm overflows release sewage during and soon after heavy rainfall, additionally rain can wash pollutants from the land into rivers.
• Pollution alerts: Check updates on The Rivers Trust sewage map for discharging sewage in your area.

Tips for swimming safely

Keeping an eye out for any of the above signs is a great first step to ensuring your safety while enjoying time in our rivers. As you spend more time in and around the water, you will become attuned to changes and adept at spotting the clues that point to poor water quality. Rivers that have designated bathing status can be a good place to start, as they are regularly tested for pollutants. Ultimately, trust your senses—if the water smells bad, looks dirty, feels oily, or seems different than usual, it’s best to stay out. If you are uncertain, swim with your head above water and make sure to shower when you get home.

Use our River Safety Routine before you swim.

Take action and help improve our rivers

Alongside taking refreshing wild swimming dips to reconnect with nature, helping to improve river health is another great way to engage with and protect our waterways. The Rivers Trust envisions wild, healthy, natural rivers valued by all, and there are many ways you can help make this vision a reality:

• Litter pick: Whether you’re walking or swimming, take a few moments to pick up any rubbish you see. Keeping a small bag with your swim kit makes it easy to collect litter on the go.
• Join your local Rivers Trust: Local Trusts across the UK and Ireland work to improve rivers in their areas. They offer opportunities to get involved in activities like river cleanups, tree planting, water monitoring, and wildlife surveys. Find your nearest Trust on our map (Member Trusts | The Rivers Trust).
• Take part in the Big River Watch: A large-scale citizen science initiative, the Big River Watch takes place twice a year, once in Spring and again in Autumn. Simply download the free app, spend five minutes observing your local river, and complete the in-app survey. You’ll record what you see, from wildlife to pollution, helping to build a picture of river health across the UK and Ireland. The next Big River Watch runs from April 25th to May 1st—why not combine it with a wild swim? The app even includes a handy pollution ID guide. Learn how to get involved at The Big River Watch | The Rivers Trust
• Share and support campaigns: Follow The Rivers Trust (@theriverstrust on all platforms) and your local Trust on social media and sign up for our newsletter to stay informed on campaigns and petitions to support. Your voice matters—help advocate for stronger protections and accountability for polluters.

In spite of the headlines, continuing to enjoy our rivers and the fantastic activity of wild swimming is essential. Not only for the myriad mental and physical benefits it provides but also because of the connection to our rivers that it fosters. Wild swimming has a brilliant way of creating a community of people passionate about protecting and improving our precious waterways – something that our rivers really need.