River Thames Sees Dramatic Drop in Sewage Pollution

The River Thames in the United Kingdom is becoming significantly cleaner, with sewage overflow volumes down 86% after the opening of a major new sewer tunnel.

“This is an important milestone for the river and a significant step towards a cleaner, healthier and more resilient Thames for future generations,” says Tess Fayers, Director of Waste and Bioresources at Thames Water.

The 25-kilometre Thames Tideway Tunnel, operational since 2025, has reduced annual storm sewage overflow volumes from more than 21 million to under three million cubic metres, based on modelled estimates. In its first year, it also prevented about 84 tonnes of sewage-derived litter from entering the river. Days associated with elevated health risks from sewage overflows fell from an average of 75.7% to 10.4%, while improved water quality is creating healthier conditions for fish and other aquatic wildlife. The results mark significant progress for a river once declared biologically dead in the 1950s.