Sewage is pouring into the rivers inside national parks at twice the rate that is occurring outside the protected areas, it can be revealed.
Campaigners described the situation as “outrageous” and said rivers and lakes in national parks in England and Wales should be the cleanest and most protected in the country.
There are 464 water company overflow sites inside national parks and the average duration of sewage spills for each site in 2024 was 549 hours – the equivalent of eight hours a day for two months. In total, there were 254,808 hours of sewage outflows in national parks last year.
A report by the Campaign for National Parks (CNP) and the Rivers Trust also found that more than half of the rivers in national parks failed to meet the good ecological status required by law. Slurry and fertiliser runoff from farms and toxic pesticides also contributed to the ailing state of the bodies of water. The national parks worst affected by sewage overflows were Dartmoor, the South Downs, the Broads and Eryri, also known as Snowdonia.
As well as rivers, national parks contain internationally renowned wetlands and sensitive chalk streams, and host a huge variety of wildlife including salmon, beavers, water voles, bitterns and eels. They are valued by millions of visitors and help reduce flood risk downstream.
The campaigners are urging the government to bring forward stricter regulations, which were promised in January, and to ensure all sewage treatment works in national parks are upgraded to the same standard required in more populated areas. The Guardian revealed a year ago that wildlife was faring worse inside national parks than outside.
“National park rivers are being poisoned, drained and neglected – if we can’t protect these, we can’t claim to be serious about ending the UK’s water crisis,” said Dr Rose O’Neill, the chief executive of the CNP. “This outrageous level of sewage reflects ageing and poorly maintained infrastructure that is ill-designed and undersized to cope with actual resident and visitor populations.”
She added: “Without change, local groups working to protect national park waterways are often swimming against the current. Water regulators and companies have ignored national parks for far too long.”
David Johnson, a technical director at the Rivers Trust, said: “This data presents a tragic tale of underinvestment and mismanagement of the rivers that flow across our most iconic landscapes. Serious action is needed to break the cycle of pollution and destruction.”
Sewage pollution across the nations has become a big political issue and in July the government promised the biggest overhaul of water regulation since the industry was privatised in 1989 and pledged new laws in 2026.
In January, the flooding minister, Emma Hardy, told parliament: “We will strengthen through new regulation the role that public bodies, including water companies, must play in delivering better outcomes for nature, water, climate and access to nature in these special places.” However, the new regulations have yet to be put in place.
A spokesperson for the Department for Environment, Food and Rural Affairs, said: “The government is taking action to clean up England’s rivers, lakes and seas, especially in our iconic national parks and landscapes. [Across the country] we’re rebuilding sewage pipes to slash pollution levels in half with over £104bn of private investment.”
The CNP-Rivers Trust report analysed data on the combined sewage overflows (CSOs) occurring in national parks. CSOs occur when raw or partially treated sewage is discharged from water works and are only supposed to happen during extreme heavy rainfall.
In Dartmoor, the average hours of overflow per CSO was three times that outside national parks in England and Wales last year, in the South Downs and Broads it was 2.9 times, the New Forest 2.6 times and Eryri 2.4 times. Some rivers are particularly affected with, for example, the Lymington River in the New Forest national park having suffered 2,800 hours of sewage outflows in 2024.
Dartmoor also had the longest total duration of sewage releases, 49,076 hours in 2024, with Eryri second worst with 47,187 hours. Only two of the 13 national parks had sewage spill rates better than the rest of the country: Northumbria and North York Moors.
A bar graph showing sewage outflows per hour in 13 national parks
One reason for the disparity is that sewage treatment works deemed to be serving fewer than 2,000 people are not legally required to use “secondary treatment”, which removes organic matter, and therefore offer only basic water treatment.
The report found only 42% of water bodies in the national parks were classed as having good ecological status. That was better than the 12% of rivers in healthy condition outside national parks.
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But with 57% of rivers in national parks failing to meet the minimum, legally required state, “there is still a hell of a long way to go”, said Gareth Ludkin at the CNP. “The [sewage infrastructure] is no longer adequate, and probably never has been, for large influxes of people visiting the parks – it’s just out of date and defunct.”
The South Downs is the national park most affected by water industry sewage, which is cited as a reason for 80% of its failing rivers. Pollution from farming is also a significant issue in most parks, listed as a reason for 76% of the failing water bodies in the Broads.
Overall, about half the failing rivers in national parks are the result of farm or sewage pollution, or both. In addition, a toxic chemical cocktail is polluting some rivers and lakes in national parks, the report said, including pharmaceuticals used by people and flea-killing chemicals used on dogs.
Vanessa Rowlands, the chair of National Parks England, praised the work of the national park authorities, communities, farmers, landowners and government agencies in making the ecological condition of national park rivers better than those outside. But she said: “We need to go further and faster. Waterways are the cornerstone of our habitats. Yet, as the report illustrates, our efforts are hampered by poor infrastructure, lack of investment and weak regulation.”
Hazel Tranchant, from South West Water, said: “Dartmoor experienced high storm overflow hours in 2024, and we recognise we need to do more to reduce spills.” She added that 2023-24 was the wettest hydrological year on record, “which made this a challenge”.
She said a quarter of the 62 CSOs in Dartmoor already met the legal requirement of fewer than 10 spills a year, with another quarter to be improved by 2035, and the rest by 2040.
A spokesperson for Southern Water, which covers the South Downs and New Forest national parks, said: “We share customers’ desire to protect and enhance our precious national parks. Over the next five years, we’re targeting the four most active New Forest outfalls and 13 priority overflows in the South Downs, to bring all spills below the government targets. We’re also upgrading wastewater treatment works across both areas.
“Groundwater forcing its way into sewers causes most storm overflows in these areas, but through innovative relining and replacements we’re tackling this problem.”
A spokesperson for United Utilities, which covers the Lake District national park, said: “We are wholeheartedly committed to helping improve water quality across our region and in our national parks. That’s why we’re delivering the largest ever environmental investment programme in the north-west.”
The CNP is calling for the new water legislation to include legally binding targets to clean up rivers, lakes and streams in national parks, meaning all CSOs must be fixed by 2035; all sewage works must have secondary treatment; all waterways must achieve at least good ecological status; and toxic chemicals must be banned. It also wants stricter regulation and support for farmers to better manage slurry and muck spreading.
Anglian Water and Dŵr Cymru Welsh Water, which cover the Broads and Eryri national parks respectively, did not respond to a request for comment.
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