Environment Agency storm overflow spill data for 2024

The Environment Agency has today published water company Event Duration Monitoring (EDM) Annual Return data for 2024 showing the frequency and duration of spills from storm overflows in England.  

The data for 2024 shows a 2.9% decrease in the number of sewage spills compared to 2023. Spill durations increased by 0.2% – this is the number of hours overflows operated for compared to last year. This year’s data shows that storm overflow spill counts and duration remain unacceptably high.

The data also shows that in 2024:   

• The average number of spills per overflow was 31.8 compared to 33.1 in 2023 and 32.6 in 2020; 
• 39% of storm overflows spilled less than 10 times in 2024 compared to 40.5% in 2023 and 40% in 2020; 
• 12.5% of storm overflows did not spill at all in 2024 compared to 13.9% in 2023 and 13% in 2020. 

In January, the Environment Agency worked with partners to secure the largest commitment of actions and investment from water companies to clean up our waterways since privatisation. The Water Industry National Environment Programme (WINEP) sets out over 24,000 actions water companies must take over the next five years to meet their legal requirements for the environment, representing a £22.1bn investment – around £10.2bn of which will be used to improve storm overflows in England, including nature-based solutions which reduce the amount of rainfall reaching overflows.

To meet our requirements, water companies have committed to upgrading over 2,500 storm overflows – which is expected to reduce annual sewage spills by 85,000. Water companies will also install 3,500 monitors at emergency overflows sites, further protecting and enhancing 13,500 km of river.

Chair of Environment Agency Alan Lovell said: 

This year’s data shows we are still a long way off where we need to be to stop unnecessary sewage pollution. But it also provides vital intelligence that drives targeted investment. Using our Event Duration monitoring analysis, we have worked with partners to secure £10.2bn from water companies to improve storm overflows in England.

While these improvements get underway, we expect water companies to do what customers pay it to do: ensure their existing assets are maintained and operating properly.

We will continue to protect our precious water quality and resources by holding water companies to account.

The Environment Agency puts permits in place for storm overflows to ensure they are only used legally during times of rainfall and snowmelt.

We have significantly ramped up our monitoring of water companies in recent years. There is more monitoring of storm overflows in place than ever before and data-driven analytics led by our increased workforce is helping us to map discharges against rainfall more effectively.

The transparency this provides allows us to understand the scale of the issue at hand and gives the industry a clear framework to focus their investment and improvements.

It also informs our compliance and investigation work. Where significant pollution incidents occur, we work to stop the pollution as quickly as possible and then to take enforcement action where necessary. Since 2015, we have concluded 65 prosecutions against water and sewerage companies – securing fines of over £151 million. At the same time, we’re tightening the rules around storm overflows. The Water Special Measures Act will give us increased legal powers to take stronger enforcement action against environmental lawbreakers.

We recently updated our Storm Overflow Assessment Framework, which places greater emphasis on water companies to investigate, maintain and improve underperforming storm overflows. We are also updating water company permits to include spill frequency thresholds and, since January, all day dry spills – no matter how small – are now classified as pollution incidents.

Reducing the use of storm overflows is vital to achieving healthier waterways. This is a long-term process, but we have the investment, mechanisms and powers to move closer towards a cleaner future.