Under the surface

Our Plastics Challenge is asking everyone who visits our waterways to pick up just one piece of litter to help clear them within a year. But while you’re busy binning what you find above the water, we’ve still got a job to do underneath…

Plastic underwater

Peter Watts

Posted on 15/07/2019

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The issue of plastic pollution on our inland waterways isn’t simply about the unattractive appearance it gives our canals and rivers – plastic can cause real damage to the ecology of the canals, often beneath the waterline where it cannot be seen. As with the planet’s oceans and seas, much of this comes from microplastics – tiny pieces of plastic less than 5mm long, which enter the water from a variety of sources. “The actual problem is very similar as it is for marine wildlife,” says Peter Birch, national environmental policy advisor with the Canal & River Trust. “A lot of animals will see small fragments of plastic and that will trigger a feeding reflex. We don’t have gory pictures of our animals with their stomachs full of plastic but we know that will be happening as we see it elsewhere.”

Research earlier this year at 10 UK sites revealed that microplastic pollution existed in all the lakes, rivers and reservoirs that were tested. More than 1,000 small of pieces of plastic per litre were found in the River Tame, near Manchester, while the Thames was found to have about 80 microplastic particles per litre. The Trust has found microplastics in the sediments of canals at levels ranging from low to among the highest found anywhere to date. Plastic and microplastics in the inland waterways could also be heading to the sea at one of the 20 locations where canals or rivers connect with tidal water or larger rivers. The Trust has calculated that over 1,562 items of plastic leave the waterways every day.


Watch our underwater footage to see the sorts of pollution typically found in our inland waterways.

Microplastic may also introduce toxins into the water and the food chain, with research by the National University of Singapore finding more than 400 types of bacteria on 275 pieces of microplastic. “There’s a risk of toxicity from plastic as well,” says Birch. “Plastic production involved additives and chemicals that allow plastic to do their job. The science is pretty unclear as to what happens when plastic breaks down in the environment, but plastic can take hundreds of years to fully degrade and break down and we are concerned about the effect this has on the ecosystem.”

The Canal & River Trust is looking at measures it can take to capture and contain some of the plastic on its waterways. There are a variety of solutions, such as the use of booms, which are placed at weirs to stop boats travelling over the weir but happen to be very good at collecting plastic. The Trust is also trialling the use of more specific pieces of kit such as air bubble barriers and the sea bin. The former creates a screen of bubbles by pumping air through a tube at the bottom of a waterway. Waste rises to the surface on the bubbles, which can be used along with the natural current to guide plastic into a place where rubbish can be collected. “We use them on the Lea and around Little Venice,” says Birch. “We are starting to think about other areas where we have large scale problems. A bubble barrier at the top of a lock near the sea would help prevent rubbish from going down the flight and into the ocean, and make it easier for us to collect.”

Sea bins can be used around yacht marinas. These are floating bins that sit just below the surface of the water and which draw in water as well as floating debris, plastics and microplastics. Again, these bins ensure that rubbish is contained in a single place, making them easier to empty. The bins themselves can be made from recyclable material and can capture 1.4 tonnes of debris per year if emptied regularly. Finally, one solution for rivers is the more straightforward horseshoe-shaped receptacles that can be placed at strategic locations and which use the natural current to help collect rubbish.

Read more about how we protect and care for our waterways.

Jerry Hoare