Sewage overflow

Press Release: The Rivers Trust responds to the publication of storm overflow data for 2020 by the Environment Agency

Rebecca Duncan


Data released today by the Environment Agency (EA) shows that storm overflows (SOs) discharged untreated sewage and storm water more than 400,000 times, and for more than 3 million hours during 2020 in England. This is a shocking volume of untreated contaminated wastewater reaching our rivers and shows that our current approach and infrastructure, managing storm water in particular, needs a radical overhaul.

Publishing event duration monitoring (EDM) data is vital to understanding the extent and impact of sewage pollution on rivers and The Rivers Trust welcomes this first public release by the EA. The increase from 862 (6%) to 12,092 SOs being monitored since 2016 is also an important step, as we now have monitoring in place for 80% of the known SOs in England. The EA and water companies have committed to complete coverage by the end of 2023.

Michelle Walker, Deputy Technical Director of The Rivers Trust, said: “It’s good to finally see this data in the public domain, and in particular the significant increase in the number of overflows being monitored over the last four years. Despite that, we are a long way from it being understandable and accessible to the general public, so we will be updating The Rivers Trust national sewage map with the new data in the next few days. Every river has unmapped overflows in addition to the 14,630 which are declared, and we are keen to make use of citizen science to locate those and let water companies and the environment agency know where they should direct their action.

“Whilst we know we can’t make a direct comparison to last year’s EDM data due to the 50% increase in the number of overflows being monitored, the data raises alarm bells. If storm overflows work as designed, they will discharge less than 20 times per year – when there has been extreme rainfall. When that happens, SOs prevent our homes and businesses being flooded, protecting lives and livelihoods. The 2020 data indicates that, appallingly, almost 1 in 5 overflows across England are discharging more than 60 times per year, a number which is supposed to trigger an EA investigation. This is a staggering statistic and The Rivers Trust is now calling for greater transparency and publication of real-time monitoring of overflows which are discharging more than 20 times per year so the appropriate measures can be taken to improve the situation.”

“We’ve seen an increase in the recreational use of rivers during the pandemic, and this is likely to continue into the summer under current travel restrictions. Real-time data is only linked to bathing water sites in England. This works well at the coast, but with only one bathing water site declared on a river (at Ilkley), we want to see more real time data being made available so that more river users, not just swimmers, can be informed of risks.”

Christine Colvin, Director for Partnerships & Communications at The Rivers Trust, said: “The sector has made progress in monitoring sewage pollution in a relatively short time, but the urgent work to clean up our rivers has barely begun. As government guidance identifies that extreme rainfall intensity will increase by 10% by 2050 and 20% by 2080, so the SO issue will only get worse and business as usual is not an option.

Water companies have committed to investigating and improving 800 overflows before 2025 at a cost of £1.1 billion. This will deal with only 5% of the +14,000 SOs that are declared by water companies. We want to see an accelerated investment in fixing overflows and the upstream problems that cause them to spill more frequently than they should. Significant investment in infrastructure, including innovative implementation of nature-based solutions, is required to ensure that we have a capable and resilient sewage system for the 21st Century.

It’s also important to understand the impact of what we do at a household level, such as disposing of oils or non-flushable sanitary products which can block the sewage system. If we can make this happen, as well as tackling other pollution sources from industry and agriculture, we’ll be on the right track to really clean up rivers for people and wildlife.”


The performance of sewer storm overflows cannot be compared from one year to the next while the monitoring network is being put in place and is maturing. Any comparisons that are done are potentially misleading and will not help us focus on the real issues.

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