Thames Water has released its 25-year plan to address the long-term dangers posed to the infrastructure of London and the Thames Valley by population development and climate change.

Following extensive public consultation, Thames Water's co-created Drainage and Wastewater Management Plan 2025-2050 (DWMP) sets out an innovative long-term approach to protecting the environment, reducing the risk of sewer flooding to homes, and reducing storm discharges.

The population in London and the Thames Valley region is predicted to grow by 2.5 million by 20501, while extreme weather events resulting from climate change and the loss of 'spongy’ surfaces and green areas which can absorb water is expected to put extra pressure on the company’s wastewater and drainage services.

Thames Water estimates £31.9 billion is required over the next 25-year period to overcome these societal challenges, within which £10.9billion will focus on storm overflows as part of the company’s ongoing plans to protect and enhance the health of rivers and streams 2.


Bespoke plans have been developed for both London and Thames Valley that reflect the differences in characteristics of the regions, the future challenges and the customer and stakeholder preferences for each region. Key to implementing both long-term plans will be partnership working with local authorities, communities, and customers.

For London a ‘SuDS first’ approach gives preference for nature-based infrastructure to be installed across the capital, ranging from water butts to collect rain from roofs, rain-gardens in the streets (planted areas which capture rain and surface water), and installation of swales and ponds in parks as well as wetland creation and river restoration. The DWMP prioritises nature-based infrastructure and aims to deliver sustainable drainage systems (SuDS) to over 7,000 hectares of land in London – the equivalent of 50 Hyde Parks to help combat the loss of 'spongy' green surfaces.

For Thames Valley a 'remove unwanted flow' approach specifically targets the elimination of additional water that flows into the sewers which shouldn’t be there, such as from misconnected plumbing, groundwater infiltration and surface water drainage, and prioritises areas of highly sensitive watercourses, including chalk streams.

This will take place alongside continued investment in Thames Water’s sewage treatment works to increase capacity and provide more efficiencies. The company has recently launched a £1.6 billion programme to modernise sewage infrastructure and improve river health over the next two years, including plans to upgrade over 250 sewage treatment works and sewers in London and the Thames Valley.