Thames Water is progressing the proposed South East Strategic Reservoir Option (SESRO) Project for a new 150 million m3 water storage reservoir located approximately 5km south-west of Abingdon in Oxfordshire plus strategic inter-company water transfers.
The project is intended to provide a reliable and sustainable source of water for millions of customers served by Thames Water, Affinity Water, and Southern Water in Oxfordshire and the wider South East region, and to strengthen the region’s resilience to climate change, population growth, and drought risk.
The project is being treated as a development of national significance for which development consent is required. It is intended that an application for a Development Consent Order will be submitted in autumn 2026. As part of the process a statutory consultation was held from October 2025 to January 2026. Water would be extracted from the River Thames (and potentially from a future Severn to Thames Transfer project) to be stored in the reservoir.
IWA identified impacts on navigation due to abstractions from and releases to the River Thames, including in the event of emergency releases from the reservoir, which need to be mitigated during detail design.
While accepting that a pipeline is the only feasible solution for the 300 Ml/day Severn to Thames Transfer previously proposed, IWA called for the option of transfer via the restored Cotswold Canals to be re-examined if the provision of storage at SESRO permits a lower rate of transfer over longer periods of time.
IWA welcomed the provision of a water channel to protect potential navigation via the Wilts & Berks Canal, but expressed its disappointment that some of the proposals are no longer as comprehensive as previously. As currently proposed the project will make provision for the restoration of the Wilts & Berks Canal as a water channel around the reservoir, with provision for future operational features such as locks and a connection to the River Thames. IWA put forward alternative proposals which might permit the locks and connection to be constructed during the initial construction period at a similar cost to the Thames Water proposals.
IWA encouraged the use of barge transport during construction to mitigate environmental impacts. We also supported the proposals to facilitate canoeing, paddle boarding, swimming and sailing on and around the reservoir, contributing to a multi sector reservoir which will provide public benefit in a variety of areas.
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