We’re proposing a new reservoir near Abingdon in Oxfordshire to help supply water to around 15 million people across the South East. It would play a critical role in tackling expected water shortages and would also bring lasting local benefits, including new spaces for nature, leisure, and community use.

From January 2026, the South East Strategic Reservoir Option (SESRO) project name changed to White Horse Reservoir. As our reservoir proposals have evolved, so too has their potential legacy. The proposed reservoir is a critical drought insurance policy for the next century and beyond, while also being designed as a place for people to use and enjoy for many years to come.

Thanks to everyone who shared feedback during our statutory public consultation which ran from 28 October 2025 to 13 January 2026.  Over 1,200 of you attended our nine events, both in person and online. We’re grateful to everyone who took the time to give feedback - it really does make a difference. We’re carefully analysing all the feedback received during the consultation, and your views will help us refine the proposed design and shape any mitigation measures.

The Consultation Report will be submitted, alongside all other relevant documentation required to support our Development Consent Order (DCO) application, in late 2026. This application will be made to the Planning Inspectorate, which will examine the application on behalf of the Secretary of State for the Department for Environment, Food and Rural Affairs (DEFRA).

The reservoir would be filled with water from the River Thames in the winter, when there is plenty available. When river levels drop, or demand for water increases, water would be released from the reservoir back into the river for re-abstraction downstream.

The proposed new reservoir would supply water to local customers, as well as homes and businesses across London and the South East. As well as providing a resilient water supply for the South East, the reservoir would also provide opportunities to create new habitats and increase biodiversity, as well as providing new leisure and recreation facilities. The reservoir would provide water to customers across the South East, including customers served by Affinity Water and Southern Water.

Our presence on and around the site has increased as we continue our programme of ecology, archaeological surveys and ground investigations. These surveys are an essential part of understanding the local environment and helping to shape the project design. Together, this work is building a robust evidence base to guide the next stages of assessment, mitigation planning, and the Environmental Statement that will support our Development Consent Order application in late 2026.

In 2025, as part of our ground investigations work, we undertook a series of embankment trials and built three test embankments. These trials confirmed the clay is strong and sturdy enough to build our embankments. You can find out more about this work in our Clay Compaction Trial Summary Report.