Water rushes out of a dirty pipe into a river

2023’s Sewage Deluge

New data on storm overflows in England and Wales highlights the urgency of our fight for better rivers

Emma Brisdion



Today the Environment Agency released the storm overflow spill data from water companies in England for 2023, and Dŵr Cymru Welsh Water have released the same for much of Wales.

The headlines paint a devastating picture of rivers increasingly battered by sewage.

We've looked at the data. In 2023 across England:

  • A total of 464,056 discharges were counted.
  • Untreated sewage was discharged for a total of 3,606,170 hours through storm overflows – more than double what it was last year.
  • On average, each overflow recorded 33 spills. In 2022 this was 23, and in 2021 this was 29. The Government’s target for this is less than 10 per year.
  • On average, each overflow discharged for almost 8 hours each time a spill took place.
  • Monitoring carried out on 100% of 14,318 storm overflows where monitoring was expected (a further 289 were not active or did not have monitoring requirements). In 2022 it was 96%, and the Government’s target was for 100% by the end of December 2023.

In England, 2023 was the worst year for sewage discharges since monitoring began.

Raw or untreated sewage is only supposed to be discharged by water companies into our rivers and seas during heavy rains to prevent the sewerage system from becoming overwhelmed. 2023 was a particularly wet year and the increased sustained rainfall across England will have had a significant impact on discharges.

But even more alarmingly, our recent State of Our Rivers Report shows that storm overflows contribute to at least 11% of total ecological health standard failures in English rivers – this is the real consequence of the shocking numbers in today’s gory data. Sewage is just part of the picture. Our rivers are in crisis, facing a cocktail of pollution loads on monumental scales.

In 2023 across Wales:*

  • A total of 115,525 discharges were counted.
  • Untreated sewage was discharged for a total of 1,002,324 hours through storm overflows.
  • On average, each overflow recorded 54.9 spills.
  • Monitoring carried out on 99.5% of storm overflows. In 2022 it was 96%, and the Government’s target was for 100% by the end of December 2023.

*Updated 04/04/24

These statistics now include data from Dŵr Cymru Welsh Water and Hafren Dyfrdwy.

Sewage pollution pours into the Hogsmill. Image: Toby Hull, South East Rivers Trust

CEO of The Rivers Trust Mark Lloyd, says:

"The latest figures on sewage discharges mean another distressing news day for our rivers and seas. This is just one source of pollution we can identify and rectify - and we must - because this effluent is making our rivers and our people sick.

"We must make good decisions to solve this problem, looking for integrated solutions that tackle the sewage problem along with other sources of pollution, and deliver more benefits to society too. That means working with nature as much as possible and not relying exclusively on expensive, carbon-hungry measures which transfer a large cost onto customers.

"The water industry has pledged £10.1bn in England over the next five years to tackle this problem alone. Now we desperately need government to play their part and approve that spending, to hold water companies to account, and to ensure that decisions are made for long-term environmental and societal benefit - sticking plaster solutions for short term gains are not the right approach."

Coming soon

We’re updating our sewage map

Our sewage map tool contains the sewerage network treated sewage discharges, and overflows of untreated sewage and storm water into England and Wales in 2021 and 2022. Our technical team are working on cleaning up today’s new data and integrating it into this map, so that 2023’s discharge and spill data will also be available and easy to explore. Keep an eye on our social media (@theriverstrust) and on your inbox to hear when this is published.

We will continue to dig into the data and share insights on our website, social media, and in the sewage map.

What we want


Urgency! We want the government to urgently take steps to reduce sewage pollution.

We want to see:

  • A faster implementation of sustainable drainage systems
  • To focus on working with nature and nature-based solutions in the delivery of the Storm Overflows Discharge Reduction Plan
  • Ofwat and Defra to sign off on the full ambition set out in the water companies Business Plans for PR24

Water companies

We need all water companies to publish their live data, in a standardized and usable format, so that real-time spill alerts can be seen on all of our rivers and everyone can make informed decisions about interacting with their local rivers. Thames Water’s live spill information is a valuable part of our sewage map, but to make this tool as useful as it can be to everyone, we want to see the rest of England and Wales’ water companies doing the same.

All of us

Water (and anything in it) that gets flushed or washed down our drains at home is at risk of ending up in our rivers. Our own decisions are significant, and our actions do matter – taking care to only flush pee, poo and paper, properly disposing of kitchen waste and using responsible cleaning products are all meaningful actions to take.

Take action today

Email your political representative

Wherever you live in the UK and Ireland, you can use our quick online tool to find the contact details of your local political representative and email them with our draft template. Add your own comments and demand that they stand up for our vital rivers.

Email your political representative

More information

How do we put numbers to sewage spills?

The data is called Event Duration Monitoring (EDM) data. Water level sensors detect the start and end of releases (or spills) at designated points which allow untreated sewage to overflow directly into the environment. This is how we are able to share data on the number of hours that untreated sewage has been discharged in specific locations or by individual water companies.

How does 2023 compare to the year before?

Not all sewer overflows have EDM systems installed - emergency overflows, such as those which might operate if a pump fails for example, aren't required to record spills or report these to the Environment Agency, so the data does not necessarily represent all the untreated sewage that has been discharged. The percentage of the known/permitted CSOs that have had EDM has changed each year as more monitoring has been added to the system. In 2023, 100% of England’s active storm overflows were monitored, making year-on-year comparisons with 2022 (during which 96% of storm overflows had monitoring) more meaningful and reliable than when compared to 2021, in which only 89% were monitored. Now that all known/permitted storm overflows are monitored, it will be easier to see how the situation is changing each year.

You can find out even more about the issue of sewage in our rivers, and how the data is collected and interpreted in our Sewage Map.

What do we know about the situation elsewhere?

Northern Ireland:

There is no comparative EDM data publicly available for Northern Ireland. NI Water is trialling EDM monitoring with a view to using it in the future, however, as a government-owned company, NI Water's ability to do this is dependant on it receiving sufficient funding to establish and manage the monitor network. Today they have shared modelled data on storm overflow discharges, and estimate 17,273,994 cubic m of sewage and water from Northern Ireland’s storm overflows in average year. The Rivers Trust is calling for greater investment in wastewater infrastructure to meet current and future population demands and climate pressures, and installation of wet and dry spill duration monitoring at discharge points to watercourses.


Today the i shared that sewage spills took place across Scotland’s rivers and waterways more than 50 times a day in 2022 – now accounting for an additional 5,668 on top of the initial 14,008 that were reported to the regular. While EDM monitoring in England has now reached 100% of sewage outlets, in Scotland the vast majority of outlets are still without monitoring, so the number of discharges in reality is likely to be much higher.

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