In January 2026, the UK water sector witnessed one of its most anticipated procurement milestones in recent years. Thames Water has formally launched a £5.7 billion tender to appoint a Main Works Contractor for the White Horse Reservoir, a major new water infrastructure project in Oxfordshire that’s set to reshape regional water security planning and industry contracting opportunities.
This blog explores the key developments, what they mean for suppliers and contractors, and why this tender opportunity could have long-lasting implications for the UK water industry.
What Is the White Horse Reservoir Project?
The White Horse Reservoir – previously referred to as the South East Strategic Reservoir Option (SESRO) – is a proposed new water storage reservoir southwest of Abingdon, Oxfordshire. Designed to hold around 150 billion litres of water, this scheme is one of the largest infrastructure investments in UK water infrastructure in decades.
The reservoir aims to:
- Boost resilience against drought and water stress in the South East of England
- Support long-term water supply to customers across Oxfordshire, Wiltshire, Hampshire and London
- Complement existing and future water resource strategies for multiple regional water companies
- Support the government’s housing and economic growth agenda through secure water provisioning
As such, it represents a significant contracting and supply chain opportunity for engineering, civils and water sector businesses.
Tender Details: What’s Being Procured?
Thames Water has opened the Main Works Contract tender, seeking a contractor to:
- Design, build, test and commission the White Horse Reservoir
- Provide all associated civil engineering, mechanical, electrical and infrastructure works
- Deliver the reservoir ready for operational use following testing and approvals
Prospective bidders are invited to express interest and submit a Request to Participate by 24 April 2026 – a hard deadline in the procurement timeline. After this stage, shortlisted applicants will be invited to submit detailed bids.
This makes the White Horse Reservoir tender one of the most valuable and strategically important water industry contracts currently on the market.
Why This Matters for the Water Sector
1. Scale and Sector Impact
The sheer size – £5.7bn – makes this one of the largest standalone water infrastructure tenders of the decade. It’s more than just a reservoir build; it’s a centrepiece in regional water resilience planning.
2. Strategic Procurement Model
Thames Water is leveraging modern procurement frameworks similar to major civil infrastructure programmes, encouraging competitive participation from global engineering and construction firms.
3. Long-Term Industry Opportunities
Once built, the reservoir will support water supply capabilities for up to 15 million people across multiple water company regions for decades. This means long-term maintenance, operations partnerships and supplier opportunities beyond initial construction.
Key Dates to Remember
- Open tender notice launched: January 2026
- Request to Participate deadline: 24 April 2026
- Project expected operational timeline: Estimated completion and operational readiness by the 2040s (subject to planning approvals and construction timelines)
These milestones highlight why now is a crucial period for potential bidders to prepare proposals and secure their spot in this high-value tender process.
What Happens Next for the UK Water Industry
The launch of the £5.7bn White Horse Reservoir tender marks a pivotal moment for the UK water industry. It signals a shift toward strategic, large-scale infrastructure procurement and presents significant opportunities for contractors, suppliers, and technology partners alike.
For companies aligned with water sector growth and innovation – including those in digital water solutions, telemetry, automation and intelligent networks – now is the time to align expertise with one of the most ambitious water infrastructure programmes in recent UK history.
