Thames Water Redraws Mega-Reservoir Plan Amid Local Opposition 2026

Thames Water has redrawn its mega-reservoir plan in Oxfordshire as the struggling utility seeks to convince regulators to approve the controversial project amid local opposition and warnings of "catastrophic consequences" if it doesn't proceed. The White Horse reservoir near Abingdon, designed to hold 150 billion litres of water across 6.7 square kilometres, is critical for meeting future water demands in the south-east.

Updated Plans for the Mega-Reservoir

The revised blueprint includes additional access points for construction and environmental mitigation works, such as new habitat creation. Thames Water stated it needed to carry out "targeted consultation with landowners, and those with an interest in land that may be impacted by this change." A public consultation on the original plans concluded in January, and a further consultation began last week, expected to end next month.

Cost Escalation and Timeline

The estimated cost has skyrocketed from £2.2bn to between £5.5bn and £7.5bn after a review last year more than tripled the site to 38 square kilometres to accommodate extra building works, relocate adjacent solar farms, and reroute local rivers and streams. Thames Water aims to submit a planning application by late 2026. If approved, main construction would begin in 2032, with water available by 2040, serving 15 million people.

Local Opposition and Environmental Concerns

Local groups and environmentalists have raised concerns about the reservoir's impact on the landscape, wildlife, and local communities. The expansion of the site area has intensified these worries, with critics arguing that the project could destroy habitats and disrupt local livelihoods. Thames Water insists the reservoir is necessary to cope with a growing population and climate change, but opponents question the need and the escalating costs.

Regulatory Hurdles

Thames Water must secure approval from regulators, including the Environment Agency and Ofwat, who will scrutinise the project's cost-effectiveness and environmental impact. The utility's financial stability is also under scrutiny, given its £14bn debt pile and recent credit rating downgrades. The success of the mega-reservoir plan hinges on convincing regulators that it is the best solution for water security in the region.

Key Takeaways

• Revised plans include additional access points and environmental mitigation measures.
• Costs have more than doubled from £2.2bn to as much as £7.5bn.
• Timeline pushed back: construction to start in 2032, water available by 2040.
• Local opposition remains strong due to environmental and community impacts.
• Regulatory approval is critical for the project to proceed.

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