CONSTRUCTION work is expected to begin within five years on a new £1 billion reservoir for Thames Water near Abingdon in Oxfordshire.
The utilities giant unveiled plans today (Thursday) for the mega-reservoir, which will cover 10 sq km and hold up to 150 million cu m of water.
Thames Water will now embark on a series of roadshows explaining the plans to local residents.
Abingdon was chosen ahead of 55 other potential sites in the region.
Thames Water environment director Richard Aylard said: 'Our current predictions show that by 2030 we will need an extra 280 million litres a day in London and 60 million itres a day in Swindon and Oxfordshire.
'We need a large reservoir as part of our plans to provide for our customers' long-term needs.'
Initial designs for the reservoir will be outlined during a second series of exhibitions early next year.
Building work is provisionally scheduled to begin by 2011. The reservoir is due to be completed and fully operational in 2020.
The reservoir will be three times the size of the Queen Mary Reservoir near Heathrow Airport, with just under half the capacity of Lake Windermere in the Lake District. This will make it the largest fully embanked reservoir in the country.
Thames Water chiefs are adamant that, if the new construction gets the go-ahead, it will not signal an end to the company's leak-fixing programme and conservation measures, such as installing water meters.
Mr Aylard said: 'We can and will do more to reduce the leakage from our pipes, by continuing to spend £500,000 a day on finding and fixing leaks and replacing our leakiest Victorian mains in London.
'But these measures alone will not match demand, particularly in the driest months, and that is why we need a large reservoir as part of our plans to provide for our customers' long-term needs.'