Several bubbling chalk springs provide a series of pools interspersed with woodland just outside the town, 11 miles from Winchester, where people can glimpse rare wildlife - birds like snipe and water rail, plants such as water avens, and butterflies like the marbled white.
The 75 acres make up Hampshire's most important wetland away from the coast, and it is a Site of Special Scientific Interest - but it lives or dies, says the Environment Agency, by the operation of the borehole in the nearby Hoe Road pumping station, owned by the Portsmouth Water Company.
"If it was used for more than week or two, the springs would stop flowing and the site would dry out ... It would cease to be a wetland," said Rod Murchie, the agency's areas resources manager.
"We've been aware of that for the last 25 years," said Andy Neve, the company's technical director.
"In the 1970s, we reduced abstraction by over 95 per cent. We now only use it very rarely, primarily on occasions when we have particular problems with other sources. It's not in regular use."
The company and the agency have come to a provisional agreement that the company, which has 650,000 customers, will try to seek a replacement source - but its estimated cost is pounds 3.5m.
This could be afforded if the director-general of water services, Ian Byatt, allows Portsmouth to pass this cost on to its customers in their bills; but he may not. In which case, Hoe Road will still have to be used.
"We feel we've been very careful with our abstraction," Mr Neve said.
Mr Murchie, of the Environment Agency, was adamant, however.
"The fate of The Moors hangs on the future of that borehole," he said.
"They have a `licence of right'. They can take water legally up to the licence limit, which is 11,000 cubic metres per day. If they did, it would destroy the site in a few weeks.
"They've only used it for a week or so in recent years, but their priority, of course, is to supply their customers so they will use it if necessary.
"We consider that unacceptable. It should not be used at all."Reuse content