Vale of White Horse District Council and South Oxfordshire District Councils have submitted their formal responses to Thames Water’s statutory consultation on the South East Strategic Reservoir Option (SESRO) — and the verdict is clear. The councils’ assessment is a powerful and unequivocal critique of a project that remains unjustified as best value, unsafe for people and water supplies, and unsupported by evidence of net benefit for the area for all the years of disruption and destruction.
Thames Water’s consultation was intended to demonstrate progress ahead of its planned Development Consent Order application later this year. Instead, the council’s response highlights fundamental gaps in the company’s case, echoing our long‑standing concerns.
Vale Council Leader Cllr Bethia Thomas emphasised that major questions remain unanswered. The council has already highlighted its objections in a formal letter to the Secretary of State, citing spiralling costs, flawed assumptions, and the failure to properly consider alternative solutions.
“Many questions remain around the size of the proposed scheme, its environmental impact and significant (growing) financial and carbon costs, as well as the potential for increased flood risk in local watercourses. We will continue to do everything we can within our power to ensure that the voice of our community is listened to.”
Cllr Andy Cooke, the Vale’s Water Champion, stated that Thames Water has
“still failed to make a plausible case for the damaging, disruptive and pointless giant mega‑reservoir.”
His comments underline the council’s view that SESRO’s world‑beating scale brings world‑beating risks — risks that remain unaddressed even at this late stage of design.
The councils all conclude in their consultation responses that a particularly serious concern is the absence of any credible emergency planning. They state:
“the lack of emergency plans for drawdown, accidents and disasters appears at best oversight and at worst negligence in the face of potentially catastrophic disasters”.
South Oxfordshire D C Leader Cllr Maggie Filipova-Rivers wrote to the Secretary of State on 22nd December 2025 about the Emergency Drawdown issue:
‘Under these proposals, Thames Water will have an emergency discharge facility in place which will include the ability to empty the reservoir at a rate of 1 metre of height per day, possibly over a period of 3 to 4 weeks….. The council is gravely concerned that such a discharge could cause havoc along the Thames, endangering lives, homes, businesses, communities and the environment.’
The councils’ responses reinforce what many residents already know: SESRO is a project being pushed forward without the evidence needed to demonstrate that it is safe, affordable, or that the alternatives have been properly considered.
The Vale, Oxfordshire County Council and South Oxfordshire District Council have been working in close alignment, and their response was supported by specialist hydrological analysis from Wallingford HydroSolutions. The concerns raised are therefore not isolated; they reflect a broad, evidence‑based consensus across local authorities which echo our findings.
GARD welcomes their strong stance and detailed critique. Until Thames Water can produce transparent, independently verified modelling on cost, safety, flood risk, water quality and drought resilience — and until it properly evaluates alternative
