A RESERVOIR the size of Heathrow Airport is being planned to start operating at Abingdon in just 25 years.

Thames Water also said the colossal artificial lake would have to be the biggest of all possible options – 150 million cubic metres – to meet future demand for water.

The grassroots campaign group which has battled the reservoir since 1976, GARD, warned everyone opposed must keep fighting 'otherwise it will arrive'.

John Broadbent, one of the Group Against Reservoir Development's newest members, said: "We need people to email their councillors and MPs and register their concerns.

"It is very hard to envisage what 100ft high earthworks look like but for ten years while they build this thing it's a massive disruption in the area.

"Thames Water keep saying they just listen to what people say, but we are really concerned that people don't want this.

"The more people we can get to respond to this the better."

Thames Water has been rebuilding the case for a reservoir between Marcham, Steventon and East Hanney since the plan was thrown out by Government in 2010.

It revealed the surprise 2043 operational start date in its draft Water Resources Management Plan 2019.

The company says the south east is already 'seriously water stressed' and about a quarter of the water it puts into supply is lost through leaks in its own pipes.

Looking ahead the firm warns the population it serves is set to grow by two million by 2045, but climate change means the UK seeing hotter, drier summers and less rain.

By 2100, the company forecasts that it could face a shortfall of 864m litres a day.

By comparison it currently loses 677m litres every day through leaky pipes.

Having looked at 'more than 200 options' to increase supply, the company produced four 'preferred options', all of which include a new reservoir at Abingdon.

The proposals also include an 'ambition' to cut leakage by 15 per cent and encouraging households to use less water.

The company admits the reservoir is required largely to meet London's growing water needs.

However GARD have torn Thames Waters' plan to shreds, claiming it lacks evidence and misses alternative options.

Vice chairman Brigadier Nick Thompson, a former civil engineer, said Thames Water has written off two viable options which could meet its need: transferring water from the River Severn into the Thames in times of drought, and using desalination plants to make seawater drinkable – which Thames Water already does.

Mr Thompson, who lives in Steventon, said: "Because we have had great technical arguments with them about it, they know we are their main technical opposition.

"They are very conscious that our consultant is just as well-versed in their challenges as they are."

Water workers' union the GMB also cast doubt yesterday on the 'contentious' Abingdon reservoir plan.

It instead urged Thames Water to accept an offer by the United Utilities water company to transfer water from Lake Vymwy in Wales to the Thames via the restoration of the Cotswold canals, which it said could supply 300m litres a day.

The one reprieve from yesterday's report was the fact Thames Water confirmed it is not planning to start work on the Abingdon reservoir in the next five years.

However Mr Broadbent warned that anyone opposed to the idea must act now and respond to Thames Water's consultation on its draft plan.

He said: "This has made us aware that we can't relax: if these things get accepted now, they could get swept up into other plans.

"Decisions will be made in the next few years and we very much want to keep the pressure up now."

GARD has invited people to join its upcoming public meetings at Drayton Village Hall on February 28 (7.30pm), Steventon Village Hall on March 5 (7pm), and Hanney Olde Hanney Room March 6 (7pm).

Find out more at abingdonreservoir.org.uk

Read the full Thames Water plan and leave feedback at thameswater.co.uk/sitecore/content/Your-Water-Future/Your-Water-Future/Providing-enough-water/Our-draft-Water-Resources-Management-Plan-2019