Environment Agency publishes storm overflow spill data for 2023

The Environment Agency has published its Event Duration Monitoring (EDM) data for 2023 showing the frequency and duration of spills from storm overflows in England.   

Storm overflow spills are measured by event duration monitors and 100% of storm overflows across the water network are now fitted with these, meeting the target set by the government to do so by the end of 2023. With just 7% of storm overflows fitted with a monitor in 2010, England is now a world leader in the number of storm overflows monitored.

Event Duration Monitoring data was returned from 14,318 storm overflows during the calendar year of 2023, up from 13,313 in 2022 and 12,092 in 2020. It is important to note that the increased installation of monitors over this period makes any direct comparisons of spill data over time very difficult.

The data for 2023 shows a 54% increase in the number of sewage spills compared to 2022, and a 13% increase compared to 2020. The increase in spills compared to 2022 is partly because 2023 was named by the Met Office as the 6th wettest year since its records began in 1836.

The data also shows that in 2023:

  • The average number of spills per overflow was 33 compared to 23 in 2022 and 32.6 in 2020;
  • 40% of storm overflows spilled less than 10 times in 2023 compared to 48% in 2022 and 40% in 2020;
  • 13.9% of storm overflows did not spill at all in 2023 compared to 18% in 2022 and 13% in 2020.

Environment Agency Director of Water Helen Wakeham said:   

“Whilst it is disappointing that water companies have reported an increase in sewage spills in 2023, it is sadly not surprising. We are pleased to see record investment from the water sector, but we know it will take time for this to be reflected in spill data – it is a complex issue that won’t be solved overnight.

“No other country has the level of monitoring we do, with 100% of storm overflows in England now fitted with a monitor. We are better placed than ever before to hold water companies accountable – thanks to intelligence from our new whistleblower portal, our plans to expand our specialised workforce, new enforcement powers, increased water company inspections and new tools to inform our enforcement work.”

Water Minister Robbie Moore said: 

“I have been clear that sewage pollution in our waters is unacceptable, which is why in just the last few months we announced a consultation to ban water bosses’ bonuses when criminal breaches have occurred, quadrupled company inspections next year, fast-tracked £180m investment to cut spills, launched a whistleblowing portal for water company workers to report breaches, and will soon set out our plans to ban wet wipes containing plastic.

“We demanded that 100% of overflows were monitored by the end of last year as part of our drive to improve transparency. Today’s data shows water companies must go further and faster to tackle storm overflows and clean up our precious waterways. We will be ensuring the Environment Agency closely scrutinise these findings and take enforcement action where necessary.”

A Water UK spokesperson said:

“These results are unacceptable and demonstrate exactly why we urgently need regulatory approval to upgrade our system so it can better cope with the weather.

“We have a plan to sort this out by tripling investment which will cut spills by 40% by 2030 – more than double the Government’s target.

“We now need the regulator Ofwat to give us the green light so that we can get on with it. The Government should do its bit by delivering the ten commitments it has previously made, which would eliminate tens of thousands of sewage spills.”



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