The state of Britain's rivers: Slurry, silage and sewage

I AM leaning over a small river in the beautiful village of St Agnes in Cornwall, UK, watching clear water babble through a grate and into a concrete conduit under the road. The grate is there to catch debris that might otherwise clog the waterway and prevent fish from swimming freely, says Josie Purcell at the Westcountry Rivers Trust, an environmental charity. It is clearly doing its job. There are a few sticks, some vegetation – and a crisp packet.

Downstream is the Peterville pumping station. This is supposed to help clean the water before it flows into the magnificent Trevaunance cove, a magnet for beach-goers, swimmers and surfers. The station also deals with sewage from the village. But sometimes it gets overwhelmed by heavy rain and lets untreated water gush onto the beach and into the sea. Last October, activist group Surfers Against Sewage issued a sewage warning for the cove after a section of the sea turned brown. Nonsense, said local water and sewerage company South West Water. It was just mud washed from the fields after heavy rain. Nonetheless, according to official figures, the Peterville station was responsible for 32 overspills of varying volume into the cove in 2021, totalling more than 166 hours.

These problems are a microcosm of those afflicting rivers and streams across the UK: rubbish, pollution, sewage, agricultural runoff, barriers to the movement of fish, other forms of river engineering and an ineffective waste-water system. “There are major problems facing our rivers, and they are extensive,” says Stephen Addy at CREW, Scotland’s Centre of Expertise for Waters at the James Hutton Institute in Aberdeen.

The destruction of the UK’s rivers has a long and undistinguished history. “Human impact on the landscape in the UK is widespread and it goes back thousands of years,” says Addy. But, by some measures, the situation has reached a low-water mark. There is no doubt that the effluent excesses of the recent past have been cleaned up, but the sheer scale and reach of anthropogenic change is unprecedented. In 2016, Addy co-authored a report for the International Union for Conservation of Nature on the state of rivers in the UK and Ireland. It concluded that “truly natural [river] environments that have escaped both direct and indirect human alteration no longer exist”.

The impact of agricultural waste

That stark statement is backed by assessments of the ecological health of the UK’s rivers carried out under the European Union’s Water Framework Directive (WFD). The assessment takes many factors into consideration, including the presence or absence of certain species; levels of pollutants, such as heavy metals, pesticides and nutrients; and the general condition of the habitat, such as water levels and barriers to fish migration. It then ranks rivers on a five-point scale of ecological health: high, good, moderate, poor and bad. If a river fails any one of the tests at any sampling site, the whole river is barred from achieving “good” status. In other words, most of a river can be in good shape, but be let down by one bad stretch.

The latest iteration, in 2021, found that only 2.6 per cent of the UK’s 7481 rivers and canals are in high ecological health, all of them in Scotland. Slightly more – 2.7 per cent – are bad. Just 30 per cent are good. Of the four nations that make up the UK, England’s rivers are in the worst health, with only 16 per cent good and 22 per cent poor or bad. The stream in St Agnes is too small to be included, but almost all the rivers along the north coast of Cornwall aren’t in good health.

The biggest rogue in this gallery of failure is agricultural waste, which runs off fields into streams and rivers. “Agriculture is a big problem. Sixty per cent of the failures to achieve good status are due to agricultural sources,” says Tessa Wardley at the Rivers Trust, a charity based in Callington, Cornwall. Some of this is an unavoidable consequence of farming, but much isn’t. Poorly constructed, badly maintained and under-capacity tanks for slurry (a mixture of manure and water) and silage (a kind of fermented grass used as feed for livestock) are a significant source of what is known as nutrient pollution, according to the Environment Agency (EA), a governmental body responsible for England’s ecological health. This can cause one of the main problems associated with farm runoff – eutrophication. It occurs when the over-enrichment of water with nutrients from fertiliser, slurry and manure leads to excessive growth of algae. These growths block out light for other organisms and produce lots of carbon dioxide, which acidifies the water. When the algae die and decay, oxygen levels plummet, creating dead zones. The blooms sometimes include cyanobacteria, also known as blue-green algae, which are toxic and can poison wildlife and taint drinking water. “They’re dangerous,” says Addy. Runoff can also silt up rivers and destroy fish-spawning areas.

Next on the list of shame is sewage, which afflicts more than half of the rivers that don’t attain good ecological health in the UK. Most of it plops into rivers when storm drains are overwhelmed by heavy rain. Much of the UK has an archaic mixed waste-water system where rainwater, sewage and other waste water – from baths and washing machines, for example – are combined and sent to treatment plants as one big sloppy mess. When it rains a lot, as it tends to in the UK, treatment plants can become overwhelmed, risking backflow of filthy water into homes and businesses. To prevent this from happening, water companies are permitted to release the untreated water straight into rivers. It is supposed to be an emergency measure, but according to the Rivers Trust, EA data shows that it happened more than 400,000 times in 2020 in England alone. EA data also revealed that England’s untreated waste-water pipes were open for a combined total of 2.6 million hours, or almost 300 years, in 2021. And that is just the outlets that are monitored.

Cesspits and septic tanks also contribute to sewage in rivers. Around 1.25 million rural homes in England aren’t connected to sewers and manage their own human waste. Some old cesspits and septic tanks are faulty and leach their content into rivers; a few older ones discharge straight into watercourses, though this has been illegal since 2000. This isn’t a nationally significant source of pollution, says the EA, but is a major contributor to sewage hotspots in some areas.

Pollution from “forever chemicals”

Chemical pollution is yet another major issue. According to data gathered by the EA, not a single one of England’s rivers ranks as high or even good on this score. The vast majority are contaminated with a class of industrial chemicals called uPBTs (ubiquitous, persistent, bioaccumulative, toxic substances). These are legacy industrial chemicals that leach out of landfill.

But there is a flipside to this shocking statistic – if you exclude uPBTs, 93 per cent of England’s rivers are in good chemical health or higher. This way of assessing chemical health is allowed under the WFD so that the malign and persistent presence of uPBTs doesn’t mask progress on other types of pollution.

Nonetheless, chemical pollution remains an issue. The Rivers Trust has been looking at a broader range of chemicals than is assessed under the WFD, says Wardley, and is seeing concerning signs of other organic pollutants not on the list of uPBTs. “That’s a really big worry because they’re very, very persistent,” she says. “The full impact of them is slightly uncertain, but it’s definitely not good.” Microplastics, especially from washing machine water, are another growing concern, she says. So are pharmaceuticals, either flushed straight down the toilet or present in the urine of people who take them. Waste treatment plants sometimes can’t deal with these, so they circle back into drinking water. These are part of what is known as “diffuse sources” of pollution, which include those that leach into rivers due to rainfall or surface runoff. They are much harder to monitor and mitigate than “point sources”, such as factory effluent pipes. Other diffuse sources are microplastics from tyre wear, agricultural chemicals and pollution washing out of the atmosphere. “It’s the diffuse sources of pollution that are really, really hard to identify and control,” says Wardley.

Abandoned metal mines are another major but neglected source of pollution. St Agnes is overlooked by several old tin and copper mines, including the dramatic Wheal Coates clinging to the cliffside. According to the EA, even though they closed decades ago, they still leach metals that harm insects and fish. They are one of the top 10 causes of poor water quality in the UK, despite affecting a small percentage of its rivers, mainly in the north-east of England, Cumbria, Yorkshire and Cornwall.

Yet another major issue is fragmentation by dams, weirs, sluices and other obstacles that hinder sediment transport and stymie the movement of fish and other organisms. “Our use of rivers has nearly always involved fragmenting them,” says Carlos Garcia de Leaniz at Swansea University in Wales. “The defining characteristic of non-ephemeral, natural rivers is that they flow, and the most pervasive sign of human impacts on rivers is the break in connectivity caused by artificial barriers to free flow.” In 2020, he and his colleagues published the first full inventory of Europe’s river obstacles, including small ones that have previously been overlooked. They recorded more than 1.6 million, around twice as many as the old estimate. Sixty-eight per cent were structures less than 2 metres tall. The UK arm of the project sampled 68,719 kilometres of river and found 23,719 dams, weirs, sluices, culverts, fords, ramps and other obstacles. Scaled up to the entire country, this suggests that the UK has nearly 50,000 barriers, 99.6 per cent of which are small. Many of them are obsolete, says Jack Wootton at the University of Hull, UK. According to an EU project called Amber (Adaptive Management of Barriers in European Rivers), only 3 per cent of the UK’s rivers are free-flowing.

The engineering practices of canalisation and channelisation – where a river is corralled between artificial banks and straightened – also affect how natural they are, separating them from their floodplains, preventing them from meandering and making the water deeper than it would be. “Often, you go to a river and it’s been canalised, it’s dead straight and banks are steep so there’s quite a drop into the river,” says Michael Acreman at the UK Centre for Ecology & Hydrology in Wallingford. “It’s probably being excavated out to prevent the flooding of the land alongside the river.” Natural floodplains, meanwhile, are increasingly used for housing and other developments, which prevents them from doing what they are supposed to do: store excess water and return it slowly to a river.

Reasons to be hopeful about rivers

Waterways are also an important repository of what little biodiversity the UK still has. Despite covering just 3 per cent of the land, river environments are home to 10 per cent of the country’s species. Only four of them are globally endangered – European eels, white-clawed crayfish, Spengler’s freshwater mussel and the Derbyshire feather moss – but many more are locally endangered, including water voles, white-tailed eagles, marsh warblers, Bewick’s swans and curlews. Biodiversity has an inherent value and also plays a huge part in people’s enjoyment of rivers and the health benefits that brings, says Jane Hill at the University of York, UK.

Perspective is, of course, required. Despite being in a bad way, some of the UK’s rivers have been worse. “If you look at the historical data, it can look as though our rivers have been improving, and in some cases they have,” says Wardley. “By some measures, they were even more dire than they are now.”

“Back in the 50s, I remember people saying ‘you don’t want to go near the Thames, let alone swim in it’, because it had effluent coming in from factories. But there’s been amazing strides to improve our rivers,” says Acreman. Sadly, progress has stalled. In 2021, James Bevan, chief executive of the EA, told the House of Commons Environmental Audit Committee, part of the UK parliament, that water quality was flatlining “because the two main polluters, the water and farming sectors, are not yet, in my opinion, doing enough to protect and enhance the environment”.

There are, however, some reasons for hope. There are more than 3000 completed, ongoing or proposed river restoration projects across the UK and tentative signs that wildlife is bouncing back. A few weeks ago, Purcell tells me, an unusual fish was spotted in the stream in St Agnes. It was a European eel on its way back to the Sargasso Sea, the first one seen there in a long while. Eels are a good indicator of the overall health of waterways and, like the rivers themselves, they aren’t finished yet.

Where the river meets the sea

"These form a major component of the British natural environment and are of major significance for wetland biodiversity conservation and for the many ecosystem services they provide to people," says Nick Davidson at Charles Sturt University in Albury, Australia.

Sadly, estuaries aren't in good shape. Even though 68 of the UK's have been recognised as internationally important wetland areas, they have long been under pressure from agriculture, ports, industry and urban development. At least 85 per cent of them are affected by humans and more than a quarter of their area has been lost. But the rate of development has slowed and estuaries are now widely recognised as habitats worth preserving, says Davidson.