Major milestone as Thames Water opens £5.7bn tender notice for nationally critical reservoir

• Thames Water launches a £5.7 billion tender notice to bring a contractor on board to build its nationally significant reservoir. 
• The announcement is an important step forward in delivering one of the nine new reservoirs across the UK, securing national water resilience and enabling new homes.
• The newly named White Horse Reservoir would secure water supply for 15 million people across the South East, including Thames Water, Southern Water and Affinity Water customers. 
• Around 1,800 jobs would be created during construction unlocking economic growth and opportunities to businesses of all sizes.
• Research shows 73% of people would visit the reservoir, creating a new leisure and tourism destination. 

The UK’s largest water company has today launched a £5.7bn tender notice for its proposed White Horse Reservoir in Oxfordshire. The 150 billion litre reservoir represents the largest water infrastructure investment in a generation. 

The project is one of nine new reservoirs that would provide water security for the UK, supporting the government's agenda for 1.5 million new homes, unlocking economic growth, and providing long-term resilience against climate change. 

The company is now seeking a Main Works Contractor to design, build, test and commission the reservoir which would be situated south-west of Abingdon. The proposed reservoir would supply water locally in Oxfordshire and Wiltshire, through to Hampshire and London. 

Chris Weston, CEO, Thames Water said: “The reservoir represents one of the most significant investments in water infrastructure the country has seen in decades.

“Once built it would be one of the largest in the country, providing water to millions, supporting new homes and development, and creating an exciting new destination where people can unwind and connect with nature. 

“Careers will be made and built through the reservoir’s construction with thousands of jobs created, supporting families and communities across the South East.”

Ben Ring, Major Projects Director, Southern Water: “White Horse Reservoir is an essential part of our plan to keep taps and rivers flowing in Hampshire.

“Combined with our Thames to Southern Transfer pipeline, it would supply our customers with up to 120 million litres of water a day during a drought, meaning the same amount can be left in Hampshire’s rare and sensitive chalk stream rivers – the Test and the Itchen.”

Stephen Plumb, Asset Strategy and Capital Delivery Director, Affinity Water: “As an industry it is crucial that we are planning for resilient water supplies in the future.

“Along with reducing leakage and helping customers to reduce their demand for water we are working together, across company boundaries, to ensure there are a range of schemes to deliver and support water resources in the UK.” 

Chris Taylor-Dawson, Senior Director for Major Projects at Ofwat: “Kick-starting the procurement process to select the main contractor is a significant milestone in the development of this important project - critical for securing our future water supply in the South East of England. 
 
“Building on the success of the Thames Tideway project, using a competitive third-party delivery approach will boost resilience in the sector and deliver better value for customers. 
 
“Engaging contractors at an early stage in the development of reservoir will tap into specialist expertise and innovative solutions – all of which can help lower costs in the longer term.”

An exciting new leisure and tourism destination 

To reflect the heritage and history of the reservoir’s location the company also unveiled a new name: White Horse Reservoir, replacing the name South East Strategic Reservoir Option (SESRO). 

Beyond water storage the reservoir will create a place for people and a space for nature.  Once open, it would attract visitors and boost tourism, supporting the regional economy for the longer term.

People would be able to enjoy a new visitor centre and cafe, sail and paddleboard on recreational lakes, fish from dedicated angling piers, enjoy education spaces and adventure areas. The project would create thriving habitats, with wildlife ponds, wetland mosaics, woodlands and rich grasslands.

Creating jobs and skills 

The reservoir would generate around 1,800 jobs during construction from apprenticeships to skilled trades, launching careers across the region. 

Roles created during and after construction include ecologists, geologists, archaeologists, engineers, electricians, construction managers, park rangers and sailing instructors. 
The project also represents a unique opportunity to invest in people and communities, and Thames Water is already connecting with schools, colleges and training providers to help line-up and develop a reservoir-ready workforce. 

Delivering economic opportunities across the UK
The reservoir would deliver growth across the country, creating opportunities for businesses of all sizes across the South East and wider UK, from local suppliers and regional SMEs  to specialist contractors, and larger national and international organisations.  

A secure water supply would also support new homes, schools, healthcare facilities, and community spaces, which will all require new water infrastructure.

Next steps 
Feedback gathered during Thames Water’s statutory consultation will shape its reservoir plans and inform its Development Consent Order application, ahead of submission to government later this year. Should the project be approved water is set to be available for use from 2040. 

The Main Works Contractor would build White Horse Reservoir, designing and planning construction, from excavation to building embankments and laying pipelines.

Thames Water is hosting an online Applicant Briefing on 11 February 2026 regarding the Request to Participate stage and the Main Works Contract opportunity. Applicants wishing to attend the briefing must register by 12 noon on 10 February 2026. 

Mohit Farmah, Head of Procurement & Supply Chain, Thames Water said: “We're seeking a contractor with the vision, capability and track record to deliver one of the UK's most significant infrastructure projects, ensuring value for money for our customers.

"This is project would secure water supply for millions, protect the environment and create a space that people can enjoy for generations to come.” 

Details on the tender notice process and how to sign-up to the Applicant Briefing can be found on the gov.uk website.

Interested organisations have until 24 April 2026 to submit a request to participate, after which shortlisted, applicants will be invited to submit detailed tenders.

The reservoir would provide up to 271 megalitres of water per day during drought, the equivalent to around 3 million baths.