# Abingdon Reservoir

The Abingdon Reservoir (also known as the South East Strategic Reservoir Option, or SESRO) is a long-term proposal for fresh water storage for the Home Counties. 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 with Southern Water and Affinity Water and is intended to serve all three company’s 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 150 billion litres (150 million cubic metres; 33 billion imperial gallons).
This would make Abingdon the second-largest reservoir in England by capacity, exceeded only by Kielder Water in Northumberland at 200 billion litres (200 million cubic metres; 44 billion imperial gallons), pushing Rutland Water into third place at 124 billion litres (124 million cubic metres; 27 billion imperial gallons). 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 to 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."

## 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 500-750mm. The west receives around 1800-2800mm.
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 be far from potent against long droughts
* As there is enough water to supply London now there can be in future using other, sustainable methods.
* Impacts on the ecosystem being transformed from supporting many endangered and protected land-based invertebrates, water voles, bats and hedgehogs to more water-based bird life.
* Traffic congestion and construction pollution.
* Local economic loss of many well-rooted businesses and a solar farm.
* A new, low, risk of flooding.