Last week, water companies shared their statistics showing how much raw sewage was released in England and Wales in 2021 and the numbers are again shocking. Sewage treatment works release both treated and untreated effluent via combined sewage overflows (CSO’s). These overflows are supposed to be used during high rainfall events as a pressure valve to stop sewage flooding back into homes. Analysis by The Rivers Trust revealed that 98% of the known reasons for very high unacceptable levels of spills in England were due to poor management and under-investment in the sewer system, not due to exceptional weather.
Most of the sewage treatment works in the Dee are managed by Dwr Cymru, with a handful managed by United Utilities flowing directly into the estuary. In 2021 the data shows that raw sewage was released for 53,057 hours overall on 8,368 occasions across 279 monitored CSO’s. The average number of spills per monitored CSO was 30 p.a., similar to the national average in England of 29. To view the full dataset across England and Wales visit The Rivers Trust Sewage Map here.
Peter Powell, Welsh Dee Trust CEO, said:
This data shows that our antiquated sewage systems are not working effectively for the environment and the River Dee. It’s time for our governments and water companies to drive forward with the solutions and investments needed to reduce the harm caused to the river by sewage.

Governments are currently drawing up plans to tackle CSO’s and the environmental harm they cause. In Wales, Welsh Dee Trust are supporting Afonydd Cymru’s requests to tackle CSO’s that are causing environmental harm and for a review of CSO regulations to ensure permits are unambiguous and enforceable. Action plans for CSO’s in Wales are due to be published in May.
In England, the government’s Storm Overflows Discharge Reduction Plan (SODRP) was also released last week for consultation. The Defra plan sets targets for water companies to reduce the harm caused by CSO pollution, but the target timelines lack urgency. The Defra timelines are even slower than the commitments already made by some water companies, like United Utilities who have already committed to reducing the number of spills from storm overflows by at least a third by 2025. SODRP only aims to improve 14% of overflows by 2030!
We want to see much more ambition to protect rivers like the Dee that are important for people and wildlife and Welsh Dee Trust will be replying to the consultation with concerns that the plans do not go far or fast enough.