Abridged
Pollution is not always easy to spot but there are visible indicators that can reveal whether rivers are in a good ecological state writes the UK’s Graham Lawton in the February 25th 2023 issue of “New Scientist.” Here are some extracts.
Looks can be deceiving when it comes to the state of UK rivers. I recently spent sometime by the Far River run south west England., which looks beautiful and pristine, but is far from it.
Yet it has been dubbed the most polluted river in England.
Last year the “Independent” newspaper analysed Environmental Agency data on sewage spills in England and found the Fal is the most fouled river in the country. That seems shocking but such events are an inbuilt feature of the wastewater treatment system in the area. They happen after heavy rain. This is a combined system that mixes sewage and household drainage water with rainwater and sends it all to treatment plants.
“It’s archaic,” says Tessa Wardley at the Rivers Trust, a conservative charity based in Cornwall.
One way then is to gauge the likely health of your local river is to find out whether your sewage system is combined with rainwater runoff.
To get a better idea of the state of a river in the UK, you can check its ecological and chemical status according to assessments by the Environmental Agency in England and its counterparts in Scotland, Wales and Northern Ireland.
On ecological health there are five categories ranging from high to bad. Figures released by the Joint Nature Conservation Committee, which advises the UK government, show that none of England, Wales and Northern Ireland’s rivers is in the highest category and only 8 percent of Scotland’s rivers reach this standard.
On chemical pollution, rivers are either classed as good or failing, based on allowable concentrations of 52 priority substances. According to these assessments, every single one if England’s rivers its failing.
“It’s really becoming apparent that, actually, the chemical state of rivers is really, really poor,” says Tessa Wardley of the Rivers Trust.
The list of pollutants is long, pesticides and fertilisers, ‘forever chemicals’ such as per-and poly fluoroalkyl substances, factory effluent, micro plastics, microfibres, medications, that have been flushed down the toilet, paint thinners, and cooking oil chucked down the drain, detergents, car wax and so on.
Without a chemical testing kit, however there aren’t many obvious signs off these pollutants. But there are visual clues.
Although for water quality, it is difficult to judge by simply looking at the water itself.
“Rivers are often quite murky and people think I wouldn’t jump in there but very often that’s just sediment,” says Tessa Wardley. “They collect colour from their geology, so they’re not necessarily polluted, but really you can only tell if you start looking at the plants and animals.”
Smaller species are a good starting point. In terms of water quality there could be issues such as a very high algae cover or even in extreme cases, blue green algae which is dangerous.
Tessa Wardley says a total giveaway is the presence of so-called sewage fungus, a gross looking filamentous bacteria that thrive in nutrient polluted water.
Larger flora and fauna are good indicators of river health.
The presence of fish is a positive sign. They rely on a good supply of macro-invertebrates in the river and they’re an indicator of good water quality.
The presence of fish is a positive sign. They rely on a good supply of aquatic invertebrates which need a healthy habitat.