Previously known as South East Strategic Reservoir Option (SESRO)
From January 2026, the South East Strategic Reservoir Option (SESRO) project name is changing to White Horse Reservoir, with a strapline of ‘a space for nature, a place for people.’
As our reservoir proposals have evolved, so too has the potential legacy it could have. The proposed reservoir is a critical drought insurance policy for the next century and beyond – but it’s also being designed as a place for people to use and enjoy for many years to come.
At this exciting stage in development, it’s important that we give the project a new identity: one that better reflects the crucial role it will play in shoring up water supply, as well as the broader benefits it will deliver for future generations.
It is the same project, with the same vision, but with a new name that will help people recognise it more easily. For us, the name White Horse Reservoir roots this project in local heritage and in the natural world around us. Equally important as the project’s new name, the strapline tells us more about where the project’s strengths lie; a space for nature, a place for people.
You can find information about the reservoir project below and in the document library.
Project update
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. The reservoir would also bring lasting local benefits, including new spaces for nature, leisure, and community use.
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 9 events, both in-person and online. We’re incredibly grateful to everyone who took the time to give feedback - it really does make a difference.
We're aware that a small number of people have been unable to submit longer comments due to a character limit on the online form. While we have found it sufficiently generous for the vast majority of responses and during other consultations, we want to make sure everyone can have their say. As such, if you wish to submit a long response to our consultation, please email sesro@ipsos.com. We'll accept responses up to 23 January 2026.
We’ll carefully analyse all the feedback received during the consultation. 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 (PINS), 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 proposals for the new reservoir have been overseen by RAPID (Regulators’ Alliance for Progressing Infrastructure Development), a consortium of water industry regulators. RAPID has implemented a ‘gated’ regulatory process to ensure that all new strategic water supply options are considered in a fair, consistent and transparent way, and that our customers’ money is spent wisely.
More information about RAPID and the gated process, including technical reports, additional information provided to RAPID, and feedback from RAPID relating to the project can be found here.
We intend to submit an application for a Development Consent Order (DCO) in 2026, seeking permission to construct and maintain the new reservoir. If granted, construction is forecast to begin in 2029 with the reservoir planned to begin operating in 2040. The planning process will allow people to have their say on the proposed new reservoir before a final decision is made by the Secretary of State. Demonstrating that we have had regard to local and regional concerns is an important part of the DCO process. Before formally applying for a DCO, Thames Water must carry out a public statutory consultation and consider feedback.
Find out more about the DCO process in our factsheets. More information is also available on the Planning Inspectorate website.
Working with suppliers is key to delivering these vital projects now and for future generations
Find out more about how to become a supplier
