We know our rivers are polluted—the WI has been running the End Plastic Soup campaign to protect them from microplastic fibres and many groups have been campaigning about agricultural pollution and untreated sewage.
But there is another cause of pollution that doesn’t get mentioned so much: surface water run-off from roads, towns and cities. This contributes nearly a fifth of pollutants.
Surface water drains are intended to take clean rainwater, and in many cases end up in water courses with no treatment. But the rainwater picks up dust, microplastics from tyres and brake pads, detergents from washing cars, oils from the road and a whole range of other chemicals, damaging biodiversity and the health of rivers. When there are periods of heavy rainfall, the drainage systems can be overwhelmed, and we end up with flash flooding; water treatment companies have greater volumes of water going in than they can treat, as surface water combines with foul water – one of the causes of sewage overflows.
However, there are ways of capturing much of this water before it reaches the drainage system: adding sustainable urban drainage systems in urban areas and beside roads. Features such as rain gardens, swales, reed beds and green roofs collect water and slow the flow, allowing it time to soak into the ground, and the right planting cleans it.
As climate change drives more periods of heavy rain, this is important. Such schemes can make the streets look nicer, too, with attractive areas of greenery. This video explains it all in just over 3 minutes: https://youtu.be/LMq6FYiF1mo. Asking your local councils to bring in or support such schemes can make a big difference.
If you have a garden, as well as using water butts to collect water you can build your own rain garden to catch the excess—a surprising amount of water comes down from the roof after heavy rainfall and rain gardens can soak up 30% more water than a lawn.
These links show you how to make two different kinds: https://www.rhs.org.uk/garden-features/rain-gardens and https://permaculture.co.uk/videos/how-build-rain-garden.
Green roofs also slow down water flows, and can be added to sheds and garages if you want to leave the house roof clear for solar panels.
Even simple steps, such as avoiding paving over large areas of garden with impermeable surfaces, make a big difference to flood protection. If you have a driveway, areas of low-growing plants or even gravel will slow down rainwater run-off.
Some of the surface water contamination comes from misconnections—when washing machines, sinks and other domestic water outlets that should be connected to the sewer system have been connected to the surface water system by mistake. This happens surprisingly often, so it’s also a good idea to check where your pipes go.