Thames Water has chosen Arup Binnies to help deliver a new reservoir, known as South East Strategic Reservoir Option (SESRO).

If approved, SESRO will provide a secure water supply to 15 million customers in the Thames Water, Southern Water and Affinity Water catchments from 2040.

Without the reservoir, the South East’s future water supply is at risk due to population growth and challenges of climate change.

Thames Water forecasts that across London and the Thames Valley it will need an extra 1 billion litres of water every day by 2050, with two million more people expected to live in London and the Thames Valley.


The appointment follows a comprehensive procurement exercise, where Thames Water shortlisted Technical Partners that demonstrated extensive experience in developing and supporting large complex infrastructure projects in the current UK planning environment.

The Arup Binnies joint venture brings world class expertise in major infrastructure. Separately, both organisations have supported the design and construction of London’s Thames Tideway Tunnel and are playing a pivotal role in the design of the Fens and Lincs Reservoirs.

The companies will work alongside Thames Water’s SRO team to deliver technical services in engineering design, environmental assessment, planning, and land access and acquisition.

Should Thames Water secure government approval for SESRO, as part of its draft Water Resource Management Plan, Arup Binnies joint venture will play a crucial role in ensuring the company is ready to submit a Development Consent Order (DCO) for the reservoir in 2026. If granted, construction is forecast to begin in 2029 with SESRO planned to begin operating in 2040.