Abingdon Reservoir


The Abingdon Reservoir is a long-term proposal for fresh water storage for the Home Counties. To be located south west of Abingdon, Oxfordshire in the mid-west of the Thames Basin, it is intended to help support water supply provision in the south-east of England. The proposals have been developed primarily by Thames Water, along with Southern Water and Affinity Water, as the reservoir is intended to serve all three companies' customers.

Proposals

The proposal arose in 2006 by Thames Water. In 2007 the Environment Agency opined that need for this was not proven. Further arguments were put but the near-term-demand case was rejected in 2011. In 2023, following a period of consultation, a revised version increased the proposal to.
This would make Abingdon the second-largest reservoir in England by capacity, exceeded only by Kielder Water in Northumberland at, pushing Rutland Water into third place at. Across the whole of the UK, only seven Scottish lochs have greater freshwater storage by volume.
Additional storage capacity is expected to be needed by 2043 to cater for projected population growth in the Thames Basin.
In early 2025, Thames Water opened discussions with potential contractors about delivery of the reservoir, which would cost up to £2.2bn to build and would then supply water to 15m people across southeast England. Ground investigations were in progress to help inform an application for development consent in 2026. If the consent was granted, construction was expected to start in 2029 for opening in 2040. Chancellor Rachel Reeves expressed her support for the scheme in a January 2025 speech as part of "nine new reservoirs to improve our water infrastructure and provide a foundation for growth."
A judicial review of the proposed project started on 25 June 2025, but was dismissed in the High Court on 25 July 2025. In January 2026, Thames Water started the process to appoint a main works contractor for the £5.7bn project.

Reasons for the construction

The main reason to build is that the South-East is facing significant seasonal water stress. Factors are the rain shadow behind the prevailing westerly winds and western hills. Eastern counties lack the rainfall of the west; their average annual rainfall being. The west receives around. Average population density is higher in the eastern than western counties; London houses 13.5% of the UK's population. This is the greatest concentration of domestic water usage. Roughly 22% of water use is domestic; 75% is from all types of industry.

Counter-arguments

GARD, or the 'Group Against Reservoir Development', have counter-arguments, local, national, and international comparators.
  • Thames Water have unambitious targets for leakages.
  • The reservoir will not be effective against long droughts.
  • As there is enough water to supply London now, there can be in future using other, sustainable methods.
  • The reservoir will damage the ecosystem, impacting endangered and protected land-based invertebrates, water voles, bats and hedgehogs but benefitting more water-based bird life.
  • Construction of the reservoir will cause traffic congestion and pollution.
  • Local businesses, including a solar farm, will suffer economic loss.
  • There will be a new, low, risk of flooding.