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UK waterways: what are the biggest sources of pollution? And is there a solution?

Many of us are aware that the UK’s waterways are heavily polluted. However, many more of us will be shocked to discover that not a single river in the UK is in a state of good health. River health is measured based on the chemicals present and the state of the ecology – the plants and animals – living in the waterway. It is hugely concerning that no UK river has reported a good chemical status and that only 14% achieve a good score for ecology. 

To solve this crisis we need data; we need people like you to step outside and investigate the quality of your waterways. As you take your first measurements, you are bound to wonder where all this pollution has come from. But do not leave your questions unanswered. Take a few minutes to familiarise yourself with the biggest sources of water pollution in the UK. From agriculture to mining, this blog explains the lot.


A staggering 40% of UK waterways are affected by agricultural pollution from rural areas. If practised sustainably, agriculture need not be such a significant polluter. However, intensive farming and the excessive use of fertilisers and pesticides negatively impact water quality.

Fertilisers and pesticides both cause serious problems. Spread on fields to increase the growth of crops, these substances contain high quantities of nitrates and phosphates which are highly nutritious for plants. As rainfall washes pesticides and fertilisers from fields, these nutrients flow into nearby water bodies. 

One specific impact of this run-off is eutrophication. Eutrophication occurs when excessive levels of nitrates, phosphates and other nutrients enter a body of water. In high concentrations, these nutrients accelerate the growth of algae. As algae dominates a waterway, it blocks sunlight from reaching below the water’s surface. Without sunlight, aquatic plants cannot survive and this negatively impacts fish populations. In areas of eutrophication, fish populations often migrate away or, in extreme cases, die out.

Intensive farming of livestock and poultry is also hugely detrimental to the health of our waterways. Large quantities of animal faeces are often deposited into nearby rivers. Not only is this harmful to plants and animals, but if untreated water is ingested by humans, it can also pose a serious health risk. Only if there is greater collaboration between the agricultural and water industry, will good quality be guaranteed for all. 

Water companies

With the issue receiving extensive media coverage during 2022, pollution from water companies is extremely topical. The scale of the problem is enormous. Last year in England, water companies expelled raw sewage into rivers a total of 372,533 times. This means that untreated sewage flowed into our waterways for 2.7 million hours1

You may be surprised to hear that some of this expulsion is planned and legal. There are around 15,0002 combined sewer overflows (CSOs) in England, designed to prevent sewage overflowing during times of heavy rainfall. These CSOs discharge untreated sewage directly into rivers and streams, but must have a permit to operate under UK law. However, there are 184 unregulated pipes across the UK3 meaning that, not only is the discharge from these pipes unmonitored, but is also illegal. As a result of both legal and illegal discharges, faecal bacteria, microplastics and sewage-related litter all end up in our waterways.

Even treated sewage causes problems. Firstly, treated sewage is usually warmer than the rivers into which it is released4. Secondly, the substances used to treat wastewater do not all naturally occur in our waterways. Both the warmer temperature and the wastewater treatments can be harmful for aquatic plants and animals. 

Surface runoff from urban areas

When it rains, the water is usually taken in by the soil. However, when there is more water than can be absorbed, the excess flows over the ground until it reaches a waterway. This process is known as surface runoff. While it always occurs naturally, it has been exacerbated by human activities – especially in urban areas. 

In our cities, we have an abundance of tarmac. Roads, driveways, streets and carparks all leave little open soil. This means that when it rains, the excess water cannot easily be absorbed by the earth. Instead, it runs quickly over these smooth, tarmacked surfaces. In this manner, microplastics from car tyres, grit for our roads and even spilled petrol are all transferred directly to our waterways. 

Once present, these urban pollutants create a harmful domino effect for aquatic life. Algae or plankton absorb the pollution which is then transferred to any animal which eats them. The toxic pollution congregates in the bodies of the largest predators as they consume an accumulation of pollution from their collective prey.

Mines and quarries

The Environment Agency estimated that over 1,500km of rivers in England are polluted by metals from mines5. As metals are mined, extracted and processed, waste is produced that cannot be sold. In the industry, this is known as ‘tailings’. These tailings are often released directly into waterways, where they cause extensive damage.

Unlike other forms of pollution, metals do not degrade over time. Extremely toxic, these metals have a long-lasting negative impact upon the environment. Even pollution from a hundred years ago can still cause harm!

The impact of water pollution through mining can depend on the type of technology used to extract it and the make-up of the metals mined. For instance, if a metal is more pure, it requires less processing and less waste will be produced. However, when you consider the longevity of metal pollution, even the lowest impact activities are still incredibly detrimental to our waterways.

Pollution solutions

Buffer zones

Guidance from the Environment Agency specifies that buffer zones should be established along waterways6. Buffer zones refer to designated areas in wetland areas adjacent to waterways that serve to protect them from agricultural pollution and surface runoff from urban areas7. When planned correctly, these zones create significant benefits for the surrounding ecosystem. For example, a project in Bristol installed buffers along a section of the River Avon8. Very quickly, vegetation began to regenerate in the buffer zone which, in turn, provided additional food sources for wildlife. Significant improvements to fish stocks were also reported. The success of projects like this suggests that buffer zones should be seriously considered to combat waterway pollution.

Nature-based solutions

Forest restoration, soil regeneration or conservation efforts are all examples of nature-based solutions.These initiatives offer great potential for protecting waterways from pollution. For instance, healthy soil and greater tree cover can both reduce surface runoff. When soil is not overly compacted, it can absorb more water. Trees draw up water from the ground as they photosynthesise, meaning that less water runs over the earth’s surface and into waterways. Combining buffer zones with soil and tree projects could be an extremely effective method of preventing pollutants from flowing into our waterways.

Protection against boating

The cumulative effect of small amounts of pollution from boating can be highly detrimental to water ecosystems. However, several actions can be taken to reduce these negative consequences. Keeping engines well maintained limits the likelihood of leakages and special environmentally-friendly boat paint can reduce the amount of toxins entering a waterway. 

1 https://www.statista.com/statistics/1180077/water-company-sewage-discharges-england-rivers/
2 https://consult.defra.gov.uk/water-industry/storm-overflows-discharge-reduction-plan/
3 https://www.channel4.com/programmes/britains-water-scandal-dispatches
4 https://pubs.rsc.org/en/content/articlehtml/2021/ew/d1ew00411e?page=search
5 https://consult.environment-agency.gov.uk/environment-and-business/challenges-and-choices/user_uploads/pollution-from-abandoned-mines-challenge-rbmp-2021-1.pdf
6 https://www.gov.uk/guidance/guide-to-cross-compliance-in-england-2016/gaec-1-establishment-of-buffer-strips-along-watercourses
7 http://www.environmentdata.org/archive/ealit:2202
8 https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/291658/scho0210brxw-e-e.pdf

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