There are now only two days left to respond to Thames Water’s statutory consultation on the proposed South East Strategic Reservoir Option (SESRO) — a large new reservoir planned to the south-west of Abingdon, between Drayton, Steventon and East Hanney. The consultation closes at 11.59 pm on 13 January.

The proposal is for a 150-billion-litre reservoir to serve around 15 million customers. Thames Water says the scheme is needed because the South East is ‘water-stressed’ due to climate change, population growth and limits on river and groundwater abstraction. Thames Water also loose water through leaks.

The company expects to submit a Development Consent Order in autumn 2026, with the reservoir planned to be operational by 2040.

Preparatory work has been under way to find out how they can best use material found on site. Clay compaction trials are being carried out to test how the local clay — taken from different depths and in different combinations —  can be best used for building the reservoir’s earth embankments.

Since the consultation began in October, Thames Water has held seven in-person events, including one in Abingdon.

The scheme remains controversial. Vale of White Horse District Council continues to oppose it, having concerns about its scale, environmental impact, rising costs, carbon emissions and flood risk. The campaign group GARD (Group Against Reservoir Development) argues that the project has grown substantially in cost and land take, and that alternative ways of getting water supplies should be reassessed.

Local MPs have also been raising questions in Parliament, particularly about Thames Water’s recent record.

Layla Moran, MP for Abingdon and Oxford West, said, ‘I would not trust Thames Water to run a bath, let alone deliver a project of this size.’

Olly Glover, MP for Didcot and Wantage, said ‘Concern about some of Thames Water’s plans is widespread and impossible to ignore, because of Thames Water’s performance and track record.’

With the consultation now in its final two days, this is likely to be the last opportunity for the public to influence the proposals. Even brief comments are counted, and you do not have to answer every question.

The consultation can be found here:
https://thames-sro.co.uk/public-consultations/south-east-strategic-reservoir-option-sesro-statutory-consultation-2025/

The brochure I used when responding is here:
https://thames-sro.co.uk/media/k40ndnes/statutory-consultation-brochure-2025-interactive.pdf

The GARD website for an opposing view and a guide to responding to the consultation is here:
https://groupagainstreservoirdevelopment.org/2025/12/06/consultation-response-guide/.

The South East Strategic Reservoir Option (SESRO) – now renamed the White Horse Reservoir rather than the Abingdon Reservoir – is currently the subject of a Statutory Consultation. Yesterday there was a display in the Guildhall in Abingdon given by Thames Water, working with Affinity Water.

The Roysse Room, featured models of the reservoir and embankments, and a 3D ‘drive-round’ video.

Information boards were set up in the Magistrates Court.

There were more design documents and appendices for those who need more details.

The large reservoir proposed near Abingdon has been progressing through the national RAPID “Gate” process, which reviews major water-resource schemes at 5 gateway stages to ensure the scheme is viable and affordable and wanted at each gateway before progressing.

At Gate 1 in 2021, the project was confirmed as technically feasible as a concept.

By Gate 2 in 2022, Thames Water had fixed the preferred size at 150 million m³ and estimated the delivery cost to about £2.2 billion (Ofwat SESRO Case Study).

Now at Gate 3 (2024–25), after detailed site and engineering work, the projected cost has risen sharply. The consultation documents suggest a range of £5.5–£7.5 billion. (It will be paid for by customers of the water companies over about 100 years.)

This led Vale of White Horse District Council in October 2024 to warn of ‘spiralling costs’ and call for a rethink, questioning whether such an expensive scheme is the best long-term solution for the region’s water supply (VWHDC statement).

Inside the Guildhall, the case was being put for the reservoir. Outside, a representative of GARD (Group Against Reservoir Development) handed out summaries of the case against.

New GARD objections, alongside long-standing environmental and community concerns, involve the escalation in cost and the expanding size of the scheme. The reservoir area now requires 38 km² of land – not only for the reservoir itself but also to restore lost biodiversity, relocate solar farms (some will float on the reservoir), mitigate flood risks, and reroute watercourses.

The consultation materials are available online at SESRO statutory consultation 2025. The consultation runs to 13th January 2026.

Gard material can be found at groupagainstreservoirdevelopment.org.

There’s a proposal to build a huge reservoir near Abingdon. It would cover farmland, roads and buildings between Drayton, Steventon, East Hanney and Marcham. The road from Steventon to East Hanney would be diverted and farmland and wildlife habitats lost.

This week, campaign groups (CPRE and Safer Waters) who tried to challenge the plan in court were unsuccessful. They are now hoping to take their case to the Court of Appeal.

The reservoir is being promoted as part of the solution to future water shortages. The reservoir would store enough water to supply 15 million people across the South East. But some local people and campaign groups are concerned it will damage wildlife, take away farmland, and change the local landscape and cause flooding.

Earlier this year, after years of local opposition to this and earlier proposals for a reservoir, the rules changed when Steve Reed, the UK’s Environment Secretary, approved the project and made it a Nationally Significant Infrastructure Project. That means local councils no longer have the final say. Instead, Thames Water can submit its plans to the Planning Inspectorate. After a public review, a government minister would then decide whether the project can go ahead.

The full planning application is likely to go to the Planning Inspectorate in 2026. If approved, construction could begin in 2029, and the reservoir could be ready from around 2040.

The Stop the Reservoir signs, seen in the villages surrounding the proposed SESRO reservoir site,

are now appearing in Abingdon town centre.

They raise concerns about the reservoir’s impact, particularly the potential rise in the water table – up to one metre.

Explaining the Water table rise of one metre, the Gard site says, ‘On February 13th 2024 Thames Water gave a presentation on Flooding and SESRO  to Oxfordshire County Council, District Councils and other stakeholders . Its engineer from Mott MacDonald clearly stated that the Reservoir if constructed would cause a 1.0 metre rise in Groundwater level, requiring considerable ‘mitigation’. For the villages of East Hanney and Steventon this would greatly worsen existing flood conditions.’

The UK government has approved the construction of a £1.2 billion reservoir near Abingdon as part of a national water management plan. Local councils and community groups oppose the project, citing environmental concerns and lack of public consultation, and have initiated legal action.