Christian M. 7 min read

Fertiliser Pollution in Rivers

Fertiliser pollution poses a significant threat to the health of the UK’s rivers, with 70% of nitrogen and 25% of phosphorus in UK waters attributed to agricultural runoff.

The idyllic River Wye has become a globally renowned case where nutrient runoff from intensive poultry farming has led to severe ecological damage, including a 90% loss in its Ranunculus weed beds and severe declines in fish species like Salmon.

This article delves into the complexities of fertiliser pollution, examining its sources, impacts, and the efforts to mitigate its effects, using the River Wye as our main case study.

Join us as we uncover the challenges and prospects in the fight against fertiliser pollution.


What is fertiliser pollution?

Fertilisers are widely used in British agriculture to supply plants with nutrients such as nitrogen and phosphorus required to optimise crop production. Fertiliser pollution occurs when excess fertilisers run off from agricultural fields into water bodies.

This runoff can lead to a process known as eutrophication, which causes harmful algal blooms. These blooms deplete oxygen levels in the water, leading to the death of aquatic life and significant disruption of ecosystems.

Additionally, fertiliser pollution can degrade water quality, making it unsafe for drinking, recreation, and other uses. The overall impact is detrimental to both the environment and human health.

What are fertilisers made of?

Fertilisers are made of essential nutrients such as nitrogen, phosphorus, and potassium. They may also contain secondary nutrients like calcium, magnesium, and sulphur, as well as trace elements such as iron, manganese, zinc, copper, molybdenum, and boron. Their components are not toxic themselves, the issue arises when the excess is washed into waterways, causing eutrophication.

What are the main sources of fertiliser pollution in the UK?

The main sources of fertiliser pollution in the UK are agricultural activities. According to DEFRA, agriculture contributes approximately 70% of the nitrogen and 25% of the phosphorus entering UK waters. Excess application, improper timing, and runoff from fields are key contributors to this pollution.

💡 Did you know?

Heavy rainfall significantly exacerbates fertiliser pollution when rain washes excess fertilisers from fields into water bodies, making the timing of applying fertiliser crucial in mitigating pollution. Can an improvement in weather models be the answer?

How polluted are UK rivers?

UK rivers are significantly polluted, with no river in England or Northern Ireland meeting the “good overall health” criteria. Only 15% of rivers in England, 31% in Northern Ireland, and 50% in Ireland achieve good ecological health standards. Agricultural runoff is a major source of this pollution, along with sewage pollution and chemical contaminants.

The impacts of fertiliser pollution in UK rivers

The impacts of fertiliser pollution in UK rivers are summarised by the following tables:

Impacts on aquatic ecosystems

These are the main impacts on aquatic ecosystems:

EutrophicationExcess nutrients cause dense algal blooms, blocking sunlight and disrupting aquatic food webs.
Oxygen DepletionDecomposing algae consume oxygen, creating hypoxic "dead zones" where marine life cannot survive.
Altered Water QualityChanges in nutrient levels affect water chemistry, impacting species sensitive to these changes.
Toxic Algal BloomsSome algal blooms produce harmful toxins, which can accumulate in the food chain, affecting aquatic life.
Loss of BiodiversityHypoxia and altered water quality lead to the decline or extinction of sensitive species, reducing biodiversity.

Impacts on human health

These are the main impacts on human health:

Contaminated Drinking WaterNutrient runoff contaminates drinking water with nitrates and toxins, posing health risks.
Recreational HazardsHarmful algal blooms can cause skin rashes, respiratory issues, and gastrointestinal illnesses.
Economic ImpactsIncreased water treatment costs due to the need to remove excess nutrients and toxins.
Food Safety ConcernsContaminated fish and shellfish can accumulate toxins, posing health risks to consumers.
Public Health CrisesLarge-scale algal blooms can lead to health advisories and crises, requiring significant resources.

Listing these impacts gives us a limited understanding of this issue. For this reason, we use the following case study to exemplify them.

Case Study: Fertiliser pollution in River Wye

Fertiliser pollution is a complex, multi-faceted issue involving small businesses, corporations, farmers, both local and the UK government, the state of the economy, local residents, etc.

As such, the best way of understanding this interplay is through notable case studies, with the River Wye currently being the most high-profile case of fertiliser pollution in the UK. Let’s dive in.

The River Wye

The River Wye is the fourth longest river in the UK, stretching for 250km from the deep Welsh hills all the way to the Severn Estuary in England. It’s a historic river, known for its beauty, but recently it has been facing severe fertiliser pollution challenges, primarily due to agricultural activities involving the use of poultry manure.

Poultry farms

The catchment area, especially the area around Herefordshire, has housed poultry processors for a long time, but a sharp rise has been seen over the last few decades, with numbers increasing by one third between 2013 and 2017 alone. Over 20 million birds are still being housed at any time.

While multiple companies operate the poultry farms, Avara Foods have the highest market share. The company is the result of a recent merger between two poultry giants who are now the principal supplier for Tesco supermarkets.

On average, each bird generates between 1.5 and 2 pounds (0.7 to 0.9kg) of manure during its life cycle, which translates to around 15,000 metric tonnes of poultry manure being generated annually.

Poultry manure fertiliser

Poultry manure is a great natural fertiliser, high in content of essential nutrients, particularly nitrogen, phosphorus, and potassium, which are vital for plant growth. It enhances soil texture, increasing its ability to retain moisture and nutrients, and adds organic matter to the soil, promoting microbial activity and improving soil health.

It is also cheaper than synthetic fertilisers, especially when being produced in excess, and as a waste product of the poultry industry.  However, too much of a good thing becomes bad, and its excess can lead to severe environmental issues.

Nutrient runoff

When poultry manure is exposed to rainfall, it gets leached of its nutrients, which is how plants can effectively absorb it. However, there is a limit to how much plants can absorb, and any excess will simply seep into the groundwater or runoff into nearby streams during heavy rainfall.

Nutrient runoff in the Wye catchment area is happening in two places:

  • During the improper storage of poultry manure.
  • When it is spread onto fields in excess and/or with bad timing and heavy rainfall.

Unfortunately, the spike in poultry population has not been supported with adequate storage and its appropriate use in fields (one that is well-dosed, well-timed, and with appropriate buffer zones).

A government report found that field in the Wye catchment area are receiving an excess of 3,000 tonnes of phosphorus per year over what crops and grasses can effectively abrosb. While nutrient excess is common across the UK agricultural sector, this is 2.5 times more than the average overdose.

Effects on the River Wye

In combination with the unseasonably heavy rainfalls and high temperatures of 2020, a significant algal bloom impacted around 70 miles of the River Wye, starting from Llanbister and reaching the lower stretches. This bloom caused the loss of over 90% of the river’s Ranunculus weed beds, severely affecting fish and invertebrate life​.

The subsequent decline in key species such as salmon and white-clawed crayfish, together with continuous water quality issues, has led to the River Wye’s status being downgraded from “unfavourable—recovering” to “unfavourable—declining”, a title that only a handful of British rivers hold.

In contrast, other rivers like the Thames and Severn that have historically suffered from severe fertiliser pollution in the past are now categorised as “recovering” or have altogether become “favourable”.

This is exemplified by Orthophosphate concentrations, which have reduced to 15-20% of their levels in 1990 in many English rivers. In contrast, the Wye continues to struggle with concentrations reaching as high as 0.1 mg/l in many sections, which is two to five times higher than typical values in other rivers.

Mitigation efforts

Following local protests, media attention and official reports, multiple initiatives have been launched to try to contain the problem:

Nutrient Management Plans (NMPs)

The Environment Agency (EA) and local stakeholders have implemented these to identify sources of phosphorus pollution and promote best agricultural practices to reduce nutrient runoff.

These have been so far supported by government grants and local environmental funding schemes, with initial reports suggesting a modest reduction in phosphorus levels so far, and highlighting the need for continuous monitoring.

Integrated Wetlands Projects

A comprehensive network of existing wetlands are being revamped or expanded to absorb excess nutrients before they reach the river. Some of these include:

  • Lugg Meadows (50 Ha) and Herefore Wetland (40Ha), near Hereford
  • Gwent Levels (25 Ha) and Clydach Vale (25 Ha) in South Wales
  • Plynlimon (30 Ha) in Mid Wales

These projects are funded by environmental grants and government initiatives, including contributions from the Sustainable Farming Incentive (SFI) and other local and national environmental funding sources

Catchment-sensitive farming

Advisers are working with farmers to adopt practices that minimise nutrient runoff, such as creating buffer strips along watercourses and improving manure management.

This is in combination with collaborative efforts involving local councils, environmental groups, and the farming community aims to restore the river’s health through sustainable practices and enhanced monitoring.

So far, reports show positive changes in farming practices, with many farmers adopting recommended measures.

Regulatory actions and funding

Increased inspections and enforcement of regulations are being carried out, especially in Wales, alongside funding for infrastructure improvements, such as better slurry storage and manure processing facilities.

Government allocations include up to £35 million for infrastructure improvements and manure processing facilities​.

Legal action against Avara Foods

A multi-million-pound legal claim has been launched against Avara Foods, alleging that their poultry farming practices are a significant source of phosphorus pollution in the River Wye.

As of May 2024, the case is ongoing, with significant media coverage and public interest. It is supported by law firms representing affected residents and environmental groups​

Outlook for fertiliser pollution in the River Wye

We remain cautiously optimistic. While the initiatives are taking place to reduce eutrophication and plummeting water quality, the issue is very complex. The amount of poultry farms hasn’t decreased despite the pressure and water quality in the Wye remains low.

Worsening climate change adds an extra layer of complexity, with more unpredictable rainfall patterns and rising temperatures only supporting the growth of algae.

Ironically, the River Wye is one of the most popular rivers in the UK for multi-day canoe trips, largely because of its well-developed infrastructure for camping and public facilities that support such expeditions. It is renowned for its scenic beauty, relatively gentle flow, and the availability of designated campsites and stop-off points along the route.

The future of fertiliser pollution in UK rivers

The UK government only got serious about tackling fertiliser pollution in rivers when it implemented the Farming Rules for Water in 2018.

These rules mandate best practices for nutrient management and are responsible for the government initiatives we covered in our case study of the River Wye, like Catchment Sensitive Farming (CSF), Nutrient Management Plans (NMPs), and environmental land management schemes.

While we remain optimistic, how long it will take depends on the effect of existing complexities and worsening climate change.

Everyone plays a part in river pollution

Ultimately, everyone capable of leaving a water footprint must play their part in keeping British rivers clean, including both the domestic and business water stakeholders that make up the British water industry.

So far, the deregulation of the British water market (i.e. turning it into an open market where business water suppliers can compete with one another) has not brought about a material change in the sustainability of the industry despite the introduction of green business water tariffs.

However, increased media attention is ramping up the pressure on the government to do something to reduce the environmental impact of the water industry. There are positive developments, like improving greywater systems, water leak fixing campaigns, smart water meters, all of which are helping reduce water consumption, making it more sustainable, and keeping it cleaner.

Remaining positive, even during adverse conditions, will be key in the fight to keep water supplies ample and clean in the UK.

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