Residents are being given the chance to influence the design of a £1bn reservoir that could swallow up an area the size of 900 football pitches.

If built, the Thames Water reservoir, between Abingdon and Wantage, would have half the capacity of Lake Windermere and would be the biggest embanked reservoir in the country.

On Saturday, the company unveiled more details of the construction and impact of the facility that will serve the future needs of Oxfordshire, Swindon and London.

The exhibition, at Abingdon's Guildhall, was the first in a month-long series of public consultations aimed at giving residents a say in the reservoir's design and recreational facilities.

A new access road would be built running south from the A415 to alleviate traffic in the villages.

New railway sidings would have to be built between Steventon and Grove to bring in sand and gravel.

And a section of the Wilts and Berks canal would be restored to allow the reservoir to be drained into the Thames for maintenance work to be carried out.

The company also unveiled different levels of recreational use, ranging from a nature reserve with minimal buildings, to a plan including water sports, visitor centre, clubhouse and equestrian centre.

Thames Water project manager Malcolm Orford said the exhibitions, the second phase of the company's consultation process, were to hear the views of the local community.

He said: "It gives the local community the opportunity to come and speak to us about their concerns and influence the final design; what do they want the reservoir to look like and be used for? It has to work as a reservoir, but there are opportunities beyond that.

"This is about showing people what it would look like and what other uses it could have."

Mr Orford said the company would use feedback from residents to help produce the final designs for the scheme.

Those designs would be unveiled to the public early next year before a formal submission was made to the Government.

He said the Government would almost certainly ask for a public inquiry into the plans, taking the process to 2010.

If granted permission, the reservoir itself would then take a further eight years to build.

Exhibitions will be held in Abingdon, Steventon, East Hanney, Wantage, Marcham and Drayton.