CPRE Oxfordshire Demands Urgent Review as Reservoir Costs Spiral
25th November 2025
New figures from water industry documents show that the price of the Southeast Strategic Reservoir Option (SESRO) has jumped from around £2.2 billion in 2022 to about £6.6 billion today – a dramatic price increase which raises major questions about whether the reservoir is still affordable, necessary, or good value for water bill payers.
Despite this massive cost increase, there has been no public explanation from the regulators or Thames Water on how this will affect the project or customer bills. This lack of transparency is damaging public trust.
CPRE Oxfordshire also supports evidence from the Group Against Reservoir Development (GARD), suggesting the huge new price tag means other solutions – like fixing leaks, recycling water, using water transfers or boosting conservation – may now be far cheaper and less damaging.
A spokesperson for GARD said:
“SESRO’s costs have spiralled beyond anything previously suggested, and the case for the reservoir simply no longer stacks up. Before pushing ahead, regulators must pause, look again at the evidence, and consider alternatives that could deliver more water at a lower cost and with less environmental harm.”
Not only have the cost tripled, but the land take is now around 38 km2, roughly six times larger than the proposed reservoir area: a similar size to Oxford city.
CPRE Oxfordshire is urging regulators to:
- Pause the project and properly reassess whether the reservoir is still needed
- Compare its costs and benefits again against all other options
- Explain publicly how the cost increases will affect water bills and future planning
The charity warns that pushing ahead without this review would be unfair to customers, bad for the environment, and could lock the region into an expensive mistake.
CPRE Oxfordshire has written to national water regulators asking for a clear and urgent response. Councillor Bethia Thomas, Leader of Vale of White Horse District Council, has also written to the DEFRA SoS requesting a rethink of the reservoir.