Inquiry into Thames Water's 5,000-acre reservoir plan

Environmentalists hope the company will be stopped from destroying Oxfordshire farmland

The future of London's water supply will come under scrutiny in a five-week public inquiry starting this Tuesday, pitting environmentalists against the privately owned group Thames Water.

The inquiry will decide if Thames Water's 25-year strategy to meet the demand of 8.5 million people living in London and the Thames Valley should be amended or recommended to the Government.

The major controversy is the plan for a £1bn reservoir in Oxfordshire which Thames Water believes will be vital for security of water supply from around 2025. Campaigners from the Group Against Reservoir Development (Gard) will argue that the facility, which will cover 5,000 acres of farmland, is unnecessary and will be a blight on the countryside, destroying natural habitats. They also argue that the investment would inevitably be passed to consumers in raised water bills and increased carbon emissions.

Although the reservoir has been mooted for two decades, Thames Water believes that it can wait another 15 years while water-saving measures are introduced. These plans include more efficient pipes and low-flow shower heads. However, after 2025 the company thinks that it will need the reservoir in winter to hold excess water from the Thames, which can then be used at lower flowing times in the summer.

Thames Water needs to get approval soon, as it could take up to eight years to build the reservoir after what could be a lengthy planning approval process.

Richard Aylard, Thames Water's external affairs and sustainability director, will be one of three company representatives giving evidence at the inquiry. Dr Kieran Conlan, a water management specialist from environmental adviser Cascade Consulting, is expected to back Thames Water's plans.

Ed Vaizey, the MP for Wantage & Didcot, is backing Gard and the local authorities opposing the plan. He said: "It's a case of David against Goliath, as the councils have had to fight this with barely any resources. What this inquiry needs to do is investigate whether there are viable alternatives and force Thames Water to investigate them."

Alternatives include rerouting water from the River Severn into the Thames. Thames Water believes such plans would still need the construction of a reservoir, but further from the Thames.

The inquiry was called by the Department for Environment, Food and Rural Affairs last August. The draft proposals, known as the Water Resources Management Plan, were previously consulted on for 16 weeks in the summer of 2008.

Earlier this month, Thames Water opened the first major UK desalination plant to make seawater suitable for drinking. The £250m facility in Beckton, east London could supply up to a million people in times of drought. The company had a planning battle with the then London Mayor, Ken Livingstone, before starting the construction.