Thames Water redraws mega-reservoir plan amid local opposition

Thames Water has revised its plans for the White Horse mega-reservoir in Abingdon, Oxfordshire, amid strong local opposition and concerns over the project's cost and environmental impact. The reservoir is designed to hold 150 billion litres of water, covering an area of 6.7 square kilometres, making it the size of Gatwick airport.

The cost of the project has surged from an initial estimate of £2.2 billion to between £5.5 billion and £7.5 billion after the site was expanded to 38 square kilometres. The expansion was necessary to accommodate new construction works, relocate solar farms, and reroute local rivers and streams. The reservoir, initially known as the South East Strategic Reservoir Option, requires additional access points for construction and environmental mitigation, including new habitat creation.

A public consultation on the original plans concluded in January, and a new one began last week, set to end next month. Thames Water aims to submit a planning application by late 2026, with main works construction starting in 2032 and water availability by 2040, serving 15 million people. The reservoir is needed to address population growth in the south-east and the impact of climate change on water resources.

However, campaigners argue that Thames Water underestimated the costs and overestimated the strategic value of the reservoir, which has been criticized for its size, construction challenges, and potential risks. Critics have accused Thames Water of failing to consult adequately with local organizations, councils, and residents, citing a lack of comprehensive flood risk modeling and dam breach analysis despite the site's location in a red-rated flood plain.