The UK is no stranger to heavy rain and windy weather, frequently buffeted by storms blown in from the Atlantic and the North Sea. This inclement weather is reflected in the vast number of words for rain in the British language and is responsible for the lush green countryside we all know and love.
However, heavy downpours and prolonged periods of rain can overwhelm the UK’s drainage infrastructure, especially in the wetter months. This can lead to unpleasant consequences, with sewers spilling over and leaking into our otherwise pristine rivers. Sewage pollution can be incredibly damaging to wildlife and the natural environment and poses a health risk to nearby humans and their pets.
While improving the UK’s drain and sewer infrastructure is costly, the problem is only getting worse, with the number of recorded spills increasing nationally. The effects of climate change, ushering in increasingly wet weather year-round, will only add pressure to the issue.
With this in mind, the team at Utility Bidder have explored the most recent data on storm overflows in the UK. This research will reveal the parts of the UK seeing the most sewage pollution, making it into rivers and where this problem is increasing the fastest. We will also highlight the water companies responsible for the most spills in the last year.
The water companies responsible for the most sewage spills
Unlike when comparing business energy suppliers, water companies are responsible for providing services to specific areas. This means that consumers, including business customers, must stick with whichever company operates locally. Always check the water provider’s website for business rates and perform a business electricity comparison to estimate your combined utility bills.
Water companies are responsible for providing clean water and safely removing wastewater, so preventing spills and overflows is also within their remit. But which companies have the worst record for keeping sewage in the sewers?
1. Dwr Cymru Welsh – Spills 2023: 117,830
Dwr Cymru, or Welsh Water in English, is the water company responsible for the most sewage spills in 2023, recording 117,830 separate spills. This is 20,000 more spills than the next-highest number, suggesting that deep-rooted issues and challenges have led to this disparity.
As Wales is a relatively sparsely populated region of the United Kingdom, many spills could be hard to reach, and infrastructure could be difficult to replace. The high level of rainfall in the area will only make these overflows more likely to occur.
2. United Utilities – Spills 2023: 97,537
United Utilities was responsible for the second-highest number of spills in 2023, at 97,537. This water company covers the North West of England, with its supply area stretching from Cumbria to Cheshire. This huge area includes many rural locations, such as the Lake District, the Forest of Bowland, and parts of the Yorkshire Dales, as well as two of the country’s biggest cities, Manchester and Liverpool.
The broad and varied territory covered by United Utilities will present various challenges when it comes to tackling sewage overflows, though, like Wales, the region’s high rainfall will likely be a contributing factor to the large number of spills.
3. Yorkshire Water – Spills 2023: 77,761
Yorkshire Water recorded the third-highest number of spills in 2023, at 77,761. This water company is the primary provider of water services in all four Yorkshire counties, though there is some crossover with other providers near the Yorkshire borders.
While Yorkshire is home to several large cities, such as Leeds, Bradford, York and Sheffield, the region is most well known for its beautiful countryside and national parks. However, the high prevalence of sewage spills could threaten the pristine natural environments and British wildlife found in areas like the Yorkshire Dales, North York Moors and Howardian Hills, while spills in more populated areas could be putting people’s health at risk.
Dwr Cymru Welsh Water also saw the most significant increase in spills, with 31,553 more spills recorded in 2023
1. Dwr Cymru Welsh – Spills Increase: 31,553
Dwr Cymru Welsh Water had the most significant increase in the number of spills, with 31,553 more in 2023 than in 2022. This increased the gap in recorded spills from just over 17,000 to more than 20,200, further cementing the company’s record for having the most sewage spills in the United Kingdom.
2. United Utilities – Spills Increase: 28,292
United Utilities saw the second-largest increase in spills, rising from 69,245 in 2022 to 97,537 in 2023. While the gap between Welsh Water and United Utilities increased during this time period, so did the difference in spills between United Utilities and the company with the next most spills, almost reaching 20,000 in 2023.
3. Yorkshire Water – Spills Increase: 23,488
Yorkshire Water had the third-largest increase in sewage spills in 2023, at 23,488. This means the three companies with the most spills in 2023 also saw the largest increases in spills, suggesting ongoing difficulties with spill prevention in these areas.
Thames Water takes the longest to stop sewage spills, with an average spill duration of 11.56 hours
1. Thames Water – Average spill duration: 11.56 hours
Spills in areas under Thames Water’s jurisdiction lasted the longest, with an average duration of 11.56 hours. This is almost twice as long as Northumbrian Water, where the average spill duration was the lowest, at just 6.02 hours. Thames Water covers Greater London, Surrey, Gloucester, the Thames Valley, and small parts of other surrounding counties.
2. Southern Water – Average spill duration: 10.76 hours
Southern Water had the second-longest average spill duration, at 10.76 hours. Longer spills, like those in areas served by Southern Water, can be much more damaging to the environment than shorter spills. They clog up waterways with sewage, which then takes much longer to return to good health. Southern Water serves the areas of Kent, Sussex, Hampshire, and the Isle of Wight.
3. South West Water – Average spill duration: 9.11 hours
South West Water has the third-longest average spill duration, 9.11 hours. It serves Cornwall, Devon, and some western parts of Dorset and Somerset. The area is mostly rural, with Plymouth and Exeter as the largest urban centres. It attracts hundreds of thousands of tourists every year who come to enjoy the beaches and seaside towns, many of which could be adversely affected by the area’s long sewage spills.
Average spill durations are increasing the most under Anglian Water
1. Anglian Water – Average spill duration increase: 3.07 hours
Anglian Water has seen the most significant increase in spill durations, with the average spill lasting 3.07 hours longer in 2023 than in 2022. Anglian Water’s area includes a large amount of farmland that could be damaged in the event of large sewage spills, which makes the 55.19% rise in spill duration particularly worrying.
2. Wessex Water – Average spill duration increase: 3.04 hours
Wessex Water saw the second-largest increase in average spill duration, at 3.04 hours, just a fraction less than those seen in areas served by Anglian Water. While Wessex Water, which serves large parts of the South West of England, including Dorset, Somerset, and Bristol, has seen large increases in spill duration, the company still has a very respectable review score on Trustpilot at 4.6/5, suggesting it is an otherwise reliable provider.
3. Northumbrian Water – Average spill duration increase: 2.40 hours
Northumbrian Water, which serves the North East of England, saw the third-largest increase in spill duration, 2.40 hours. Despite this considerable increase, the company still had the lowest average spill duration in 2023, at just 6.02 hours. Interestingly, Northumbrian Water also serves parts of the East of England, trading under the names Essex and Suffolk Water.
The local authorities most affected by sewage spills
While water companies are responsible for safely removing and treating sewage and wastewater, the frequency and severity of spills can vary wildly within the areas they serve. To better understand the locations with the worst sewage spill problems, we have also analysed the data by local authority.
1. North Yorkshire – Spills 2023: 23,929
North Yorkshire is the local authority that saw the most sewage spills in 2023, with 23,929 recorded yearly. This means North Yorkshire had more than 7,000 more sewage spills than any other local authority, making it a national hotspot.
2. Cornwall – Spills 2023: 16,605
Cornwall saw the second-most sewage overflows in 2023, with 16,605 spills. The area is relatively remote and rural, attracting many visitors to its beautiful countryside and beaches. However, the high level of sewage spills in rivers could damage these pristine areas and pose a particular threat to the health of the many surfers and swimmers who enjoy the waters off the Cornish coast.
3. Country Durham – Spills 2023: 15,860
The third-highest number of spills was recorded in County Durham, with 15,860. The river Wear, which flows through Durham, could be seeing dangerous pollution levels due to the frequency of spills seen last year. Rowing is a popular sport in Durham, a pastime that these spills could put under threat while also damaging the health of local fish, amphibians and waterfowl.
Only six local authorities, Brighton and Hove, Broxbourne, Cambridge, Hackney, Harlow and Watford, saw no sewage spills in 2023.
All of these areas are located in the south-eastern corner of the country, with the most northerly being Broxbourne on the eastern border of Hertfordshire. The fact that these spill-free areas are clustered in one corner suggests that there are fewer challenges here for flood overflow prevention than elsewhere in the country, whether a matter of topography, resources, or precipitation.
North Yorkshire saw the most significant annual increase in spills in 2023
1. North Yorkshire – Spills increase: 7,729
In addition to having the highest number of spills in 2023, North Yorkshire also saw the most significant increase in spills from the previous year, with an extra 7,729. This high growth rate could cause some concern in the area, as it could benefit from action to bring these numbers down to safer levels.
2. Somerset – Spills increase: 6,021
Somerset saw the second-biggest increase, with 6,021 more spills in 2023 than in 2022. This largely rural county in the South West of England is home to the Bridgwater Bay National Nature Reserve, situated on the estuary of the River Parrett. This reserve is an important habitat for many native birds, including the Eurasian curlew, grey plover, and common shelduck, all of which could be at heightened risk due to an increase in sewage spills.
3. County Durham – Spills increase: 5,920
The third-largest increase in spills was seen in County Durham, with 5,920 more than the previous year. In 2022, there were 9,940 spills in the area, the fifth highest in the country, though the almost 60% increase in 2023 launched it into third place. As such, residents of County Durham could voice legitimate concerns about the state of wastewater services in their local area.
Spills last the longest in Test Valley, at an average of more than 17 hours
1. Test Valley – Average spill duration: 17.62 hours
The longest spills in the country were seen in Test Valley, lasting 17.62 hours on average. Named for the River Test that runs through the local authority, Test Valley has experienced some alarmingly long-running sewage spills that could have damaged local environments. The wildlife inhabiting the area’s eponymous river could be paying the price for the poor record of local wastewater services.
2. Chichester – Average spill duration: 17.01 hours
Chichester saw the second longest spills in 2023, lasting 17.01 hours on average. This picturesque cathedral city is the largest urban area in West Sussex and hosts the small River Lavant, which feeds into the waterways of the Chichester Harbour National Landscape. The longer the duration of a sewage spill, the more damage it is likely to cause, meaning the lengthy spills seen in 2023 could have damaged the important habitats found in this wetland conservation area.
3. West Oxfordshire – Average spill duration: 16.25 hours
West Oxfordshire experienced the third-longest spill in 2023, with an average duration of 16.25 hours. This largely rural local authority includes the easternmost part of the Cotswolds Area of Outstanding Natural Beauty, home to many idyllic villages and small towns. Whitney, the largest town in West Oxfordshire, suffered severe flooding in 2007 when the River Windrush burst its banks. With the average spill duration so high in recent years, further flooding could cause severe health impacts and environmental damage.
Average spill durations increased the most in Lincoln in 2023
1. Lincoln – Average spill duration increase: 10.78 hours
Leading the list, Lincoln saw the most dramatic increase in average spill duration, soaring from just 1.12 hours in 2022 to 11.90 hours in 2023, marking a rise of 10.78 hours. Lincoln is a historic city known for its medieval architecture, so its sewage and drainage systems might be under pressure due to a mix of old infrastructure in historic areas and newer developments. Maintenance and modernising sewage facilities in historic cities like this can be challenging and disruptive.
2. Kingston upon Hull – Average spill duration increase: 8.80 hours
In second place, Kingston upon Hull also experienced a substantial rise in spill durations, with the average time increasing from 4.15 hours in 2022 to 12.95 hours in 2023, an increase of 8.80 hours. The city lies upon the River Hull, where it meets the Humber Estuary, making it particularly vulnerable to flooding. It faced significant flooding, notably in 2007, which impacted the sewage systems. The geographic, low-lying nature of the region also makes the risk of sewage overflows worse during heavy rains and floods.
3. Broadland – Average spill duration increase: 8.40 hours
Rounding out the top three, Broadland reported an average spill duration increase of 8.40 hours from 3.93 hours in 2022 to 12.33 hours in 2023. The area includes parts of the Norfolk Broads, a network of rivers and lakes, and its rural and low-lying nature can complicate sewage management, particularly where infrastructure may not be as robust as in urban areas. Additionally, water levels in the Broads can influence local groundwater and sewage systems, particularly during wetter seasons.
Gwynedd saw 118.2 spills per person in 2023, the most of any local authority
1. Gwynedd – Spills per 1,000 people: 118.2
The area with the most spills per person is Gwynedd, North Wales, which recorded 13,901 spills in 2023, a spill rate of 118.2 per 1,000 people. This high number is likely influenced by factors such as heavy rainfall, the rural and mountainous terrain, including the Snowdonia National Park, and possibly ageing infrastructure.
2. West Devon – Spills per 1,000 people: 97.1
In second, West Devon recorded 5,653 spills among a population of 58,190, with 97.1 spills per 1,000 people. The area includes part of the Dartmoor National Park and is mainly rural with scattered settlements. This rural setting and its less densely populated nature could worsen sewage system issues.
3. Pembrokeshire – Spills per 1,000 people: 82.8
Pembrokeshire comes in third with 82.8 spills per 1,000 people. It’s known for its coastal national park, but this might affect the region’s sewage management strategies due to saltwater intrusion and the impacts of coastal erosion and storms. Tourism and seasonal population surges could also have an effect.
The City of London saw the most sewage spills per square kilometre
1. City of London – Spills per sq. km: 68.16
The City of London is ranked first, with 68.16 spills per square kilometre. It is the historic and financial heart of London, with an extremely high density of businesses, financial institutions, and infrastructure. Despite its small size, it has a significant amount of daily activity, including heavy traffic, construction projects, and utility works, which can contribute to frequent spill incidents. Spills in the City of London are often related to construction, roadworks, utility maintenance, and accidental spills from commercial activities like restaurants and office buildings. The limited space and constant redevelopment efforts can also make environmental incidents more likely.
2. Tameside – Spills per sq. km: 42.71
In second place, Tameside experienced 42.71 spills per square kilometre. Located in Greater Manchester, Tameside has a rich industrial history, particularly in textiles and engineering. While these industries have declined, the area still hosts several manufacturing and logistics businesses that increase the risk of spills, particularly industrial substances.
3. Plymouth – Spills per sq. km: 42.25
In third is Plymouth, with 42.25 spills per square kilometre. The city’s maritime activities, including shipping, fishing, and naval operations, contribute to fuel and oil spills in the harbour and surrounding waters. As a popular tourist destination, Plymouth also experiences spills related to recreational boating and the wider tourism industry.
What could UK rivers look like as a result of pollution?
We turned to AI to find out how famous rivers in the UK could change in the future if pollution, climate change, and sewage spills continue.
River Ouse
Continued pollution of the River Ouse could lead to severe environmental degradation, with plastic waste filling the banks. As well as the piles of rubbish, harmful algae blooms could cover the water that flows through North Yorkshire.
River Eden
AI imagery of the River Eden shows the devastating impact of pollution, with dead fish floating amid piles of waste in the water. If pollution and spills continue in the Cumbrian River, harmful contaminants could wipe out aquatic life and severely damage the surrounding environment.
River Thames
The iconic River Thames could be forever changed if this rate of pollution carries on, with waste and algae taking over. Like the River Eden, aquatic animals could be wiped out from the waters as sewage spills alter their habitat for the worse.
River Severn
At 220 miles, the River Severn is the longest in Great Britain. However, this leaves it open to widespread devastation from pollution and sewage. The waters could be dulled to a murky green by 2050, with rubbish and dead animals floating throughout.
River Wye
Currently a highlight of the Welsh moorlands, the River Wye could become an eyesore in the years to come. AI predicts that pollution and sewage spills will turn the river banks brown and cover them with plastic waste while other clumps of rubbish float in the waters.
Author Commentary
“Sewage spills continue to headline UK news as of September 2024, and they’ve been a constant nightmare for water companies and local authorities across the UK since we first conducted Utility Bidder’s Polluted Waters Report back in June 2023.
“Recent news stories surrounding the fact that untreated sewage had been pumped into Windermere – one of the most popular lakes in the Lake District – did nothing to lighten the growing pressures on water companies, and as United Utilities were at fault, our research reveals that this company was responsible for more sewage spills in England in 2023 than any other company.
“So what are regulators going to do about this? Well, the announcement that Ofwat – the UK’s water regulator – could hike water bills by £19 per year until 2030 from the start of next year. This will come as little surprise to some as the new Labour government tries to get a grip on water standards in the UK to plug the pollution pandemic we are facing, nevertheless, customers could be set to struggle and water companies are angered.
“Of those companies most challenged with rising bills and industry regulation, our findings suggest that Thames Water took the longest time to stop sewage spills, with an average spill duration of 11.56 hours. What is perhaps even more stark is that the longevity of spills increased for each of the water companies sourced compared to 2022.
“Water companies serve wide-reaching areas in the UK, and multiple local authorities in the process. We wanted to highlight the issues faced all across the country, and only six local authorities saw no sewage spills in 2023; these are Brighton and Hove, Broxbourne, Cambridge, Hackney, Harlow, and Watford.
Heading into the Autumnal months, heavy downpours and prolonged periods of rain can be expected to overwhelm the UK’s drainage infrastructure. As a result, sewage spills will continue to be an unpleasant reality and there needs to be as much information shared with UK residents as possible to highlight the current crisis.”
Methodology
We used 2023 data from the Rivers Trust’s Catchment Based Approach Data Hub on sewer storm overflows in England and Wales to find the counted spills in each local authority and per water company across England and Wales in 2023 and to compare this with figures for 2022.
We then divided the 2023 figures for the total duration of spills by the number of counted spills to calculate the average spill duration for each local authority and water company.
Images were generated using Adobe Firefly to predict how UK rivers could look with ongoing pollution. Stock photography was used as a base for image composition, and AI was prompted to generate “polluted river, green algae, plastic waste, dead fish.” The generated images were then blended with original photography using Adobe Photoshop.
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