14th January 2026
CPRE Oxfordshire has formally objected to Thames Water's proposed South East Strategic Reservoir Option (SESRO), warning that it would cause permanent harm to farmland, countryside and rural communities while failing to prove it is necessary or affordable.
While the charity acknowledges the need for long-term water security in the South East, it argues that the current reservoir proposal does not meet the standards required of a nationally significant infrastructure project.
Loss of Farmland and Rural Livelihoods
CPRE Oxfordshire's main concern is the scale of land take. Although the reservoir itself would cover around 6.7 square kilometres, the overall project footprint has grown to roughly 38 square kilometres, three times the size of Heathrow Airport. The charity estimates this would remove around 3,800 hectares of agricultural land from food production, much of it likely to be high-quality farmland.
"Losing this amount of productive farmland at a time of growing concern about food security and climate resilience is extremely worrying," said Lisa Warne, Director of CPRE Oxfordshire. "This level of damage cannot be justified without clear evidence that there are no less harmful alternatives."
The scheme would also affect multiple farms, including tenanted holdings, raising concerns about the future of rural livelihoods. CPRE Oxfordshire says Thames Water must be transparent about farm losses and set out clear compensation and support arrangements for affected farmers.
Soaring Costs and Ignored Alternatives
The reservoir is now expected to cost between £5.5 and £7.5 billion. Thames Water has failed to explain rising costs, how overruns would be avoided, or what customers would ultimately pay.
The charity is calling for a proper assessment of alternatives, including water transfers, leakage reduction and demand management, which it says could deliver water resilience at lower cost and with far less environmental damage. Given the national significance of the project, there is growing concern that regulators have failed to take a firm grip on the situation or asked critical questions about the factors driving these rising costs.
Threats to Biodiversity, Environment and Climate Impact
Thames Water's claims of biodiversity net gain have also come under scrutiny, with CPRE warning that any habitat creation must be backed by legally binding, long-term management and monitoring. It also challenges misleading landscape images showing trees planted on dam embankments, saying this is incompatible with dam safety rules. Meanwhile, the true climate impact has been massively understated: construction alone is estimated to generate more than 1.2 million tonnes of carbon dioxide, while key issues such as methane emissions, soil disposal and lost carbon storage from farmland have not been properly accounted for.
A Decade of Disruption
CPRE Oxfordshire warns that a 10-year build period would bring thousands of daily lorry movements, new access roads and diverted routes, with serious consequences for local villages, road safety and quality of life. The charity is calling for a full Strategic Transport Assessment to explain how traffic, noise, dust and disruption would be managed.
"This is a huge project with long-lasting consequences for Oxfordshire," added Lisa Warne. "Until Thames Water can provide robust evidence, full transparency and a genuine comparison with less damaging alternatives, we believe it should not go ahead."
