PLANS to build a reservoir almost as big as Heathrow Airport in South Oxfordshire have been formally returned to the table.

Thames Water's long disputed plan to build an above-ground reservoir near Abingdon has returned, after being shortlisted as a key measure to tackle London's water deficit.

It has released a report analysing dozens of options to prevent drought in the capital city, with South Oxfordshire being seen as the only viable site for a reservoir in the South East.

In response, residents are set to resurrect a dormant campaign against the expanse of water, which would sit between Drayton, Steventon, East Hanney and Marcham.

There are several options for volume with the largest being 150 million cubic metres of water - making it the UK's second largest reservoir in terms of volume, behind Kielder Reservoir in Northumberland.

The proposal is for a walled reservoir which would be up to 25 metres high in places, taller than County Hall in Oxford which stands at 23 metres tall, and span four square miles, almost as big as Heathrow at 4.7 square miles.

Campaigner Nick Thompson, a former Royal Engineer, fears the structure says the reservoir could have a massive impact on the land.

Brigadier Thompson is vice chairman of Group Against Reservoir Development (GARD), which formed in 1976 after Thames Water first surfaced Abingdon Reservoir, and has always argued Thames Water should search for alternatives to future water shortages.

He said: "I fear the reservoir would pile pressure onto land already vulnerable to flooding, and said there would be ‘massive disruption’ to traffic while building takes place."

Earlier this year, Vale of White Horse District Council earmarked land for the reservoir in its Local Plan.

It would be surrounded by landscaped sloping riverbanks, and previous plans suggest it could cost £1bn.

Brigadier Thompson said it was 'frustrating' the plan persists despite being rejected by the Government during a public inquiry in 2010, when Thames Water was rapped for not doing enough research.

GARD is set to revive its public campaign after Thames Water released its fine screening report, in which the Abingdon Reservoir ticks the most boxes to battle drought in London.

This will be used to inform a final report, due out next year, outlining how water shortages will be dealt with.

Of 55 other locations investigated for a reservoir, the document concludes: "Abingdon was the best performing site overall."

The only existing UK reservoir that holds more water is Kielder Water in Northumberland, which holds 199 million cubic millimetres.

Brigadier Thompson, 80, said: "The campaign is beginning to be reawakened by the realisation that this has not gone away.

"It's a real challenge to say it's coming back, and we have got to rally round and make objections."

The group has organised public meetings about the reservoir, the first of which is at Hanney War Memorial Hall on Monday, at 7.30pm.

GARD chairman Derek Stork, a former nuclear physicist, feared there was now a 'strong possibility' that Thames Water will favour the reservoir in its final document.

Writing in a GARD newsletter this month, he said: "They have either ignored, or over-ridden with dubious arguments, the majority of critical comments coming from stakeholders like GARD.

"Other [water] sources are less costly, less damaging to the environment, less disruptive to local communities and more robust against climate change."

Alternative options also in the most recent shortlist include desalination plants and abstraction of water from the Lower Thames.

About 90 per cent of the Abingdon Reservoir water would benefit London, with the remainder shared between Swindon and Oxfordshire.

Thames Water believes Oxford will be left with a shortfall of one million litres of water per day by 2020 if no action is taken.

Its water resource manager Alex Nickson said: "We're determined this shortfall won't become a reality.

"A major new reservoir near Abingdon remains an option.

"If we do build a reservoir, making sure we limit its impact on the surrounding area will be a big priority for us.

"Not only would it be a functional site for storing water but also a place for nature to thrive and people to make use of and enjoy, as is the case at many of our other reservoir sites, including Farmoor."

Farmer Reservoir near Oxford is 10 times smaller than the largest proposed Abingdon Reservoir.