Is it clean…?


As a group of river swimmers, we are often greeted by passers-by, usually while we are in various stages of undress: ‘ You’re mad! The river’s cold and dirty!’


We love what we do and a lot of us would swim in anything for the love of water. So when the inevitable question is asked by a passer-by – ‘Is it clean?’ – it’s fair to wonder where that question is coming from. Protective of our beloved stretch, we may well feel they are asking if our pastime is a dirty one.


While love can be blind, and as much as we would like to swim in anything, we don’t.



We all have strategies to risk-assess the water every time we swim. Is it clean enough to swim in? Intuitively and experientially, swimmers know whether the water is clean. But intuition is born of knowledge, and no swimmer should enter the water in ignorance of what is out there. The river is as seasonal as the weather, and the symbiosis between the two is your best guide.


Swimming in a river after heavy downpours is when the run-off is at its worst; pollutants are high, with sewage outfalls, farmland run-off, and industrial pollution flowing in the current – sad facts of our river lives. Swimmers will sensibly avoid these times.


Not having the data, we have to rely on looking at the water to make a judgement on whether it’s clean enough to swim in. If it’s cloudy or scummy, or if it smells, it’s not. Some of the objects that float on water occur naturally – don’t jump to conclusions – but sometimes what’s floating on the water is not meant to be there and we don’t swim.


A precise tool is a sewage map from The Rivers Trust and their campaign, Rivers Fit To Swim In, which shows you sewage discharge points and to avoid swimming downstream of them www.theriverstrust.org/what-we-do/sewage-in-rivers


Conversely, at times of very low rainfall and low flow, pollutants become stagnant and concentrated and this can mean a higher pollution threat.


Things to watch out for when you’re swimming in the summer:

Blue-green algae

  • Photosynthesising bacteria that can multiply into blooms, releasing toxins that result in smelly and bad-tasting water.

  • This can occur in stagnant warm water (lakes) in summer.

  • For swimmers and marine life, this water is very toxic. If swallowed, there can be neurotoxins (affecting the nervous and respiratory systems), toxins that can irritate or inflame the skin, or hepatotoxins (affecting the liver) that can be fatal – but extremely rare!

  • If you come into contact with blue-green algae, then get out immediately and wash yourself and your kit with warm water and soap.


And what about Weil's disease?


This one is often brought out as a reason not to swim but talk to any swim group – how many of them have had Weil’s? Be prepared to fill the silence…


  • Weil’s is a serious form of a bacterial infection, leptospirosis.

  • The chances of getting Weil’s are less than 1 in 10 million and most cases are successfully treated with antibiotics.

  • The bacteria is harboured in the kidneys of a wide variety of animals – cattle, deer, pigs, sheep, horses, dogs and rodents. Pee from any of these animals, carried into water, could carry the bacteria.

  • Found in clean streams as well as urban docks, it is likely to be concentrated at the edge of water bodies where animal pee runs into the water and the water runs slower, so the bacteria is less dispersed.

  • The most common route of infection for Weil’s disease is through a cut or abrasion.

  • Apply waterproof plasters to cuts and abrasions before swimming.

  • Shower and handwash after a swim – particularly if you have any cuts or abrasions, which should be cleared of bacterial crud.

  • Remember to handwash again after handling wetsuits – particularly before eating.






There have been defining moments throughout history where water bodies have had their spotlight moment: the first Rivers Pollution Prevention Act 1876; the revision in 1951, which cited the ‘restoring of the wholesomeness of rivers’; the first EEC directives in 1973 to protect water resources. More recently, the spotlight on plastic in the oceans and the groundswell of reaction to plastic in our everyday lives. This time, the water companies have had their duty of care thrown into sharp focus, as has the Environment agency, in the recent exposé of the discharge of untreated sewage into our rivers.


The massive increase in housing developments, coupled with an underfunded infrastructure, has seen water companies struggling to meet increased demand and this has led to our rivers being compromised by high levels of sewage pollution.


Wild swimmers and all river-users are now looking to protect what they love. It has always been the case that pollution should be in the forefront of our minds and now there are organisations and individuals who make it their business to speak truth to power and insist that the legislation around keeping our rivers clean is not only adhered to, but also improved. The work of these organisations is starting to have a positive impact.





We can get more involved in supporting action to protect our rivers through organisations like The Rivers Trust and trusts in your area, like Thames Rivers Trust, Thames21, Windrush Against Sewage Pollution and Waterloggers.



Are our rivers clean enough to swim in? Yes but its not as clean as it should be and we can all have a role in changing that.


  • We can also reduce our own water consumption, to help stabilise water use.

  • By choosing to use eco-friendly cleaning products – especially dishwasher detergents we can not contribute to further phosphates ending up in rivers creating more algal blooms.

  • Cut out garden chemicals too, as they will be washed into groundwater and eventually into watercourses.

  • Understanding what can and what can’t be flushed down the loo is so basic but important: by flushing only poo, pee and toilet paper, we can help to keep sewers flowing and our rivers and beaches clear of sanitary litter.




Lock to Lock water testing

The Lock-to-Lock team have been testing the Thames water quality for the events since 2015 and all water tests have passed with a “high” cleanliness rating. Separately, friends of the team test water quality in their various swim locations to report it back to campaign groups.


Watch for future posts from the Fresh Water Habitats Trust and river updates.








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