AFTER 16 years of controversy, Thames Water's plans for the future - including a huge reservoir three times the size of Farmoor - come under public scrutiny today.

At the Guildhall in Abingdon, the company unveils the first of a series of exhibitions outlining its plans to meet water demand over the next 20 years and beyond.

Key to its strategy is a reservoir costing more than £1bn between Steventon and East Hanney.

Today's exhibition will be the first of 16 during the next four weeks at Abingdon, Wantage, Steventon and East Hanney. But exact details of the size, appearance and leisure uses of the proposed reservoir will not be revealed until the second phase of consultations early next year.

The first phase will focus on what measures Thames Water is considering to meet the growing demand for water brought on by climate change, a growing population, housebuilding and economic growth.

All those factors are putting the region's water resources under pressure and the predictions are that water supplies will be insufficient within the next 25 years.

By 2030, Thames Water forecasts an extra 280 million litres a day will be needed for London, and an extra 60 million litres a day for Swindon and Oxfordshire.

The vexed question of water leakage will be high on the agenda of reservoir critics. Thames Water loses a third of its supply and has the worst record of all water companies for repairing leaks and replacing worn-out pipework.

The company will show how much money it is spending on plugging the leaks in an ageing mains infrastructure, particularly in London.

Extending water metering is another part of the company's strategy. Importing supplies from the north is also being examined. So is a £200m scheme for a desalination plant in the Thames estuary, but that is running into problems with the environmental lobby because of the high energy consumption such a plant would demand.

Thames Water says that even if leakages are plugged and other measures put in place, a reservoir will still be needed to secure water supplies in the future. It is the company's preferred option, using water pumped from the River Thames near Abingdon.

The controversial suggestion for a huge reservoir first surfaced in 1990. It disappeared following a public outcry, but was resurrected six years ago.

Opponents of a reservoir call it a "massive inland sea". They say that if leaks were stopped, there would be no need for a reservoir, and want "importing" water from other regions to be examined.

Although there is still a groundswell of opposition to the reservoir, there are indications that the "anti-factor" may be diminishing, however.

More people are becoming aware of the effect of climate change following water restrictions this summer, the relentless march of housebuilding in the region and booming economic activity.

A survey carried out this year by Steventon Parish Council indicated a feeling that a reservoir was beginning to look inevitable.

If that is the case, people think the Vale of White Horse District Council should squeeze the best possible deal out of Thames Water in what is called "planning gain" - developers paying towards improved roads and services.

Others see a reservoir as a major economic benefit for the county.

It would act as a magnet for tourists. There would be sailing and angling, and a haven for wildlife.

The largely flat land is not heavily populated and lends itself to a large development. Twenty years ago the area was proposed for another London airport, but the idea was rejected.

But there are fears about noise and pollution during a lengthy construction programme. Soil would have to be dug out and materials such as aggregates brought in by road and rail, putting pressure on local roads.

Thames Water is pursuing a new line in its efforts to obtain planning permission through a compulsory works order, bringing together various consents and authorisations and including the compulsory purchase of land. But like conventional planning applications, it woud be considered at a public inquiry.

The Government will have the final say.

REACTIONS - The MP for Wantage, Ed Vaizey: "I have always been sceptical about the need for a reservoir of this size and based here in an unspoilt piece of open land. I will be pressing Thames Water to show the need, not only for the extra water, but also for a reservoir.

"More can be done to reduce leaks and there are alternatives to reservoirs, not least water transfer.

"Another issue that concerns me is the position of Thames Water itself. We know that it is up for sale and is making redundancies. Can we be sure that a company in this position is able to make long-term decisions about the future of our water supply?

"I also want an assurance from ministers that they will give the Vale council the resources it needs to carry out proper investigations and to represent the concerns of local people. At present, the council is outgunned, and that imbalance needs to be redressed."

The leader of the Vale of White Horse District Council, Jerry Patterson: "This is probably the most significant development the Vale council has ever had to face and it is important we have a chance to listen to people's views about what Thames Water is proposing at all stages of the compulsory works order process. Thames Water has exhibitions, leaflets and a website explaining what they have done to arrive at their conclusions. I would urge people to find out more and then let both us and Thames Water know what they think."

The planning spokesman for the Conservative group on the Vale council, Terry Cox: "We hope Thames Water will at last address the key issues of explaining the need for a new water resource and, in particular, what measures they are taking to reduce their high level of leakage. It is important local people and the Vale council express their views at both phases of the process. The appalling period of uncertainty for people is at last beginning to come to an end."

County councillor for the Hanneys and Hendreds, Iain Brown: "Thames Water must prove the case for a reservoir against all other reasonable schemes. A scheme to transfer water from mid-Wales was first proposed in 1895 and that needs examining. More needs to be done to store floodwater and recharge underground aquifers. I am also concerned that the reservoir would rely on water from one main source, the Thames."

The mayor of Abingdon, Peter Green: "I have some concerns about a reservoir and the impact such a large structure would have, but I don't know all the facts and I shall visit the exhibition to find out more."

The chairman of Steventon Parish Council, Michael Howden: "We need to know more about the plans and see if they differ significantly from the 1991 proposals. We did a questionnaire a few months ago and the feeling was that if a reservoir was inevitable, then we must secure the best possible benefits for the area."