The Condition of Rivers in Britain: Contamination from Slurry, Silage, and Sewage

 Many of the UK's waterways are struggling, including those that appear to be in good condition. However, there are ongoing efforts to address these issues through restoration projects, and there is still much more that can be done.

Industrial wastewater flows into an estuary Robert Brook/Corbis/Getty Images

At the idyllic St Agnes village in Cornwall, UK, I observe a stream flowing through a grate, which traps debris to ensure the waterway remains unobstructed for fish to swim freely, explains Josie Purcell of the Westcountry Rivers Trust. However, downstream lies the Peterville pumping station, designed to purify the water before it enters the magnificent Trevaunance cove, a popular spot for beach-goers and surfers, and also manages the sewage from the village. 

Nevertheless, it can become overwhelmed by heavy rain, resulting in untreated water flowing into the sea. Surfers Against Sewage, an activist group, issued a sewage warning in the cove last October after the sea turned brown. Although the local water and sewerage company South West Water dismissed it as mud, official statistics revealed that the Peterville station caused 32 overflows in 2021, totaling over 166 hours. 

These issues mirror the challenges that the UK's rivers and streams are encountering, including pollution, agricultural waste, blockages to fish movements, inadequate wastewater management, and other river engineering problems, according to Stephen Addy at CREW, Scotland's Centre of Expertise for Waters at the James Hutton Institute in Aberdeen.

According to Stephen Addy at the James Hutton Institute in Aberdeen, human impact on the UK's landscape has a long history, going back thousands of years. However, the current situation regarding the destruction of rivers is unprecedented in terms of its scale and reach. While efforts have been made to clean up effluent excesses, a 2016 report co-authored by Addy for the International Union for Conservation of Nature found that there are no longer any "truly natural" river environments that have not been altered by human activity.

The impact of agricultural waste

Assessments conducted under the European Union’s Water Framework Directive (WFD) confirm the grim state of the UK's rivers. The WFD considers various factors to determine ecological health, such as the presence of certain species, pollution levels, and habitat conditions. If a river fails any of the tests at any sampling site, it is barred from achieving “good” status. As a result, most of a river can be healthy, but a single problematic stretch can compromise its overall rating.

In the latest WFD assessment, published in 2021, only 2.6 per cent of the UK's rivers and canals (7481 in total) are in high ecological health, all of them located in Scotland. A slightly higher 2.7 per cent are deemed “bad,” while only 30 per cent are considered “good.” Among the four nations comprising the UK, England's rivers are the most affected, with only 16 per cent rated “good” and 22 per cent classified as “poor” or “bad.” Although the St Agnes stream is too small to be included, most of the rivers along Cornwall's north coast are not in good health.

Agricultural waste is the primary culprit in this ongoing environmental disaster, as it flows off fields into streams and rivers. According to Tessa Wardley, of the Rivers Trust in Callington, Cornwall, “60 per cent of the failures to achieve good status are due to agricultural sources.” While some of this is unavoidable, much of it is not. Tanks for slurry and silage, poorly constructed, badly maintained, and lacking capacity, are a significant source of nutrient pollution, which can cause eutrophication. Excessive growth of algae, caused by nutrient over-enrichment from fertilisers, slurry, and manure, can block out light and produce carbon dioxide, leading to acidification of the water. When the algae die and decay, oxygen levels drop, creating dead zones. Cyanobacteria, or blue-green algae, which are toxic and can poison wildlife and taint drinking water, are sometimes part of these blooms. Runoff can also silt up rivers and destroy fish-spawning areas.

A European eel and brown trout were killed by pollution. ANDY DAVIES/SCIENCE PHOTO LIBRARY;

Sewage is another major contributor to the poor ecological health of over half of the UK's rivers. In many parts of the country, an outdated mixed waste-water system collects rainwater, sewage, and other wastewater and transports it to treatment plants during heavy rains, risking the backflow of contaminated water into homes and businesses. 

To avoid this risk, untreated water is discharged directly into rivers, which occurred more than 400,000 times in England alone in 2020, according to the Rivers Trust and Environment Agency data. Moreover, untreated wastewater pipes in England were open for a combined total of almost 300 years in 2021. Cesspits and septic tanks in rural areas, which manage human waste for around 1.25 million homes, also contribute to sewage in rivers, particularly in some areas with sewage hotspots. Although not a significant source of pollution nationally, faulty and outdated cesspits and septic tanks can leak into rivers, while older tanks may discharge directly into watercourses, which has been illegal since 2000.

Pollution from “forever chemicals”

River Tame, Reddish Vale. Warner, Joe

Chemical pollution is a major problem in England, with uPBTs being the primary issue. These industrial chemicals are present in almost all of England's rivers due to leaching from landfills. However, excluding uPBTs, 93% of rivers in England have good chemical health or higher, according to the WFD. The Rivers Trust has raised concerns about other organic pollutants, microplastics, and pharmaceuticals that are difficult to monitor and mitigate as they come from diffuse sources, such as rainfall or surface runoff. Diffuse sources also include pollution from abandoned metal mines, which are a major cause of poor water quality in the UK, despite affecting only a small percentage of its rivers.

Another significant issue is the fragmentation of rivers by dams, weirs, sluices, and other obstacles, which impede the movement of sediment and organisms. Over 1.6 million river obstacles have been recorded in Europe, with the UK having almost 50,000 barriers, primarily small structures. Canalization and channelization also impact the natural state of rivers, separating them from their floodplains and preventing meandering. Floodplains are increasingly used for development, preventing them from serving their purpose of storing excess water and returning it slowly to rivers.

Reasons to be hopeful about rivers

Waterways in the UK serve as a vital repository for the limited biodiversity that still exists. Although they occupy only 3% of the land, river environments are home to 10% of the country's species. Four of these species, including the European eel, white-clawed crayfish, Spengler's freshwater mussel, and the Derbyshire feather moss, are endangered globally. Many more, such as water voles, white-tailed eagles, marsh warblers, Bewick's swans, and curlews, are endangered locally. According to Jane Hill of the University of York, biodiversity has an inherent value and contributes significantly to people's enjoyment of rivers and the associated health benefits.

It is important to have perspective, however. While some of the UK's rivers are in a dire state, they have been even worse historically. "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 direr than they are now."

Despite progress made in improving river quality over the years, recent data suggest that water quality is stagnating due to the lack of sufficient action taken by the water and farming sectors. Nevertheless, there are over 3000 completed, ongoing, or proposed river restoration projects across the UK, and there are signs of wildlife bouncing back. Recently, an unusual European eel was spotted in the St Agnes stream, making its way back to the Sargasso Sea, indicating that the waterways and their inhabitants are not yet finished.

Reference: New Scientist


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