Thames Water South East Strategic Reservoir Option (SESRO)

Thames Water is proposing a new large reservoir on land west of the A34, Abingdon.

The proposal, now titled the White Horse Reservoir (formerly known as the South East Strategic Reservoir Option, or SESRO), is considered a ‘Nationally Significant Infrastructure Project’, which means it will be determined by a government appointed Planning Inspector.

Current status

The next major milestone for the proposed reservoir is the submission of Thames Water’s Development Consent Order (DCO) application to the Planning Inspectorate, which is currently expected in November 2026.

The project is currently in the pre-application stage.
Once the DCO application is submitted, the Planning Inspectorate has 28 days to decide whether to accept it for examination.
If accepted, the project moves into the Pre-Examination phase, when local authorities, parish councils, community groups and residents can formally register as Interested Parties and submit representations.
This will then be followed by a detailed public examination before a recommendation is made to the Secretary of State.

Consultation

A statutory consultation opened on 28 October and ran to 13 January 2026.

The Council submitted a formal response to the consultation in January 2026.

Prior to this, officers and councillors have engaged with the developer team to discuss technical matters to be assessed and as part of the pre-application process have formally responded to:

• Thames Water’s informal consultation held in August 2024. View the council’s response here.
• The Environmental Impact Assessment Scoping Opinion consultation from the Planning Inspectorate in September 2024.

Recent publications

7 September 2026: Cllr Thomas wrote a letter to Thames Water Chief Executive regarding the proposed White Horse Reservoir.
12 August 2026: Cllr Thomas received a response from Rt. Hon. Matthew Pennycook MP and Alex Badrick, Deputy Principal Private Secretary, regarding chalk streams.
10 August 2026: Cllr Thomas received a response from Thames Water regarding the White Horse Reservoir.
23 July 2026: Following the Leader’s letter of 10 July to Chris Weston, Chief Executive of Thames Water, the following responses were received from Thames Water on 23 July 2026 and on 30 July 2026.
10 July 2026: Cllr Thomas wrote a letter to Chris Walters, Interim Chief Executive, Ofwat, regarding the White Horse Reservoir.
10 July 2026: Cllr Thomas wrote a letter to the Rt. Hon Steve Reed OBE MP/MHCLG regarding Chalk Streams.
10 July 2026: Cllr Thomas wrote a letter to the Rt. Hon. Emma Reynolds MP/DEFRA, regarding the White Horse Reservoir.
10 July 2026: Cllr Thomas wrote a letter to the Rt. Hon. Emma Reynolds MP/DEFRA, regarding the White Horse Reservoir Consultation.
10 July 2026: Cllr Thomas wrote a letter to the Rt. Hon. Emma Reynolds MP/DEFRA, regarding the White Horse Reservoir DCO.
10 July 2026: Cllr Thomas wrote a letter to Chris Weston, Chief Executive, Thames Water, regarding the White Horse Reservoir DCO.
10 July 2026: Cllr Thomas wrote a letter to Chris Weston, Chief Executive, Thames Water, regarding Chalk Streams.
10 July 2026: Cllr Thomas wrote a letter to Charlie Maynard MP on the White Horse Reservoir Consultation.
12 February 2026: Cllr Thomas received a response from DEFRA to her letter of 12 November on the White Horse Reservoir (formerly SESRO).
13 January 2026: South East Strategic Reservoir Option (SESRO) – Vale of White Horse response.
3 December 2024: Southern Water Draft Water Resources Management Plan Consultation – Vale of White Horse response.
22 November 2024: Cllr Thomas wrote a further letter to the Secretary of State for Environment, Food and Rural Affairs requesting a meeting to discuss the proposed South East Strategic Reservoir (SESRO).
8 October 2024: Scoping Opinion adopted by the Inspectorate on behalf of the Secretary of State.
2 October 2024: Emma Hardy MP, Department for Environment Food & Rural Affairs wrote to Cllr Thomas in response to the letters of 25 July and 6 September.
6 September 2024: Cllr Thomas wrote a further letter to the Secretary of State for Environment, Food and Rural Affairs following the news that Thames Water’s Water Resources Management Plan 2024 has been approved.
23 August 2024: Vale response to Southeast Strategic Reservoir Option (SESRO) Summer 2024 consultation
25 July 2024: Cllr Thomas wrote a letter expressing concerns about Thames Water with a briefing note attached, to the Secretary of State for Environment, Food and Rural Affairs. The briefing note was also shared with Oxfordshire MPs, Layla Moran, Olly Glover and Charlie Maynard.
11 April 2024: Robbie Moore MP responded to Cllr Thomas’s letter of 14 February on the South east Strategic Reservoir Option.
14 February 2024: Cllr Thomas wrote a letter to the Secretary of State for Environment, Food and Rural Affairs raising concerns over the proposed reservoir in the district.
25 September 2023: Thames Water responded to the letter from Cllr Thomas of 21 September.
21 September 2023: Cllr Thomas wrote to Thames Water regarding the draft Water Resources Management Plan 2024 (WRMP24).