A PLAN to pump millions of gallons of water from the Solent into Hampshire homes can be revealed today.

Water bosses want to invest in a new £73m scheme which transforms sea water into tap water. It comes after environment experts warned that the county is heading for a water crisis unless urgent steps are taken.

The proposed desalination plant would be built by Southern Water at a site in either Fawley or Millbrook.

It would provide tap water to about 250,000 homes in times of drought or low rainfall.

The company has produced the scheme after being told by the Environment Agency (EA) that it must reduce how much fresh water it takes from the River Itchen.

The EA fears that the river's unique wildlife, including migrating salmon and the southern damselfly, will not survive if water companies continue to rely so heavily on it to supply their customers during the summer.

Therefore, it is vital that new water supply schemes are developed as the river provides about half of all public water to the region, including Winchester, Southampton and Fareham.

Southern Water has warned customers that they will see a "significant" hike in their bills to pay for the cost of developing new water sources, such as desalination or wastewater recycling, to cover the supply deficit.

However, before it starts building the desalination plant, the company has vowed to challenge the EA over the proposed abstraction restrictions on the River Itchen.

Meyrick Gough, Southern Water's water resource and planning manager, yesterday called for a full public inquiry led by a Government-appointed inspector.

He also questioned the scientific findings of the EA's eight-year investigation into the River Itchen - a habitat site of European-designated importance - which was published in November.

"The change in the abstraction licence means we would end up losing 100 million litres a day during drought conditions, which equates to about half of south Hampshire's water supply. As a result we will have to put in a lot more investment and one of the consequences of that is desalination," Mr Gough said.

A site on the western shore of Southampton Water, near Fawley power station, has been chosen as the preferred location for the desalination plant. Another site opposite the Millbrook wastewater treatment works is also being considered, while a third near the Marchwood incinerator has been ruled out.

It is likely that the plant would turn about 45 million litres of the Solent into drinking water each day, but it would need to be used only during a dry summer and in times of low rainfall.

The construction bill would be more than £73m, according to Southern Water's estimations, and operating costs would exceed £960,000 a year.

The earliest possible start date is 2012, but the planning process is likely to take far longer because desalination is an unpopular technology with environmentalists.

Opponents claim that it is unsustainable and worsens water shortages by adding to global warming because of increased carbon emissions.

Hypersaline discharge - the salt extracted from the seawater - would also be dumped back into the Solent and flushed out into the English Channel.

Another scheme being considered is to recycle effluent wastewater and pump it back into the River Itchen to boost river flow levels.

Mr Gough said that Southern Water had explored "all options" including compulsory metering, creating new reservoirs and transferring water from other parts of southern England, but desalination and recycling wastewater were the only two options that could meet current demand needs.

Taking more water from the River Test, which flows from Basingstoke to Southampton Water, was also ruled out as the EA has already imposed abstraction restrictions.

EA resource planning team leader Rod Murchie said that Southern Water's rejection of its proposed River Itchen abstraction restrictions was "unacceptable". He acknowledged that the restrictions would have a "very severe impact" on Southern Water's operations during drought years.

"What we've decided is that we need to protect a certain minimum flow from the River Itchen and when the flows approach that figure the companies have to reduce their abstraction," he said.

"So in extreme drought when flows reach 200 million litres per day then the companies have to stop their abstraction entirely, which is a large amount of water for Southern Water.

"We have worked with them on this since 2000, so they have known about this for a long time, this is nothing new to them."

Mr Murchie said that the restrictions were needed to protect the river's unique habitat.

He added: "The whole bio-diversity, right down to the invertebrates at the bottom of the food chain, have got used to fast flows and very high quality water. It's got to be clear, fast-flowing water with the sun penetrating and full of oxygen - and if you take too much water out then obviously the flow slows down and these creatures start to suffer."

He admitted that "one way or the other" it would be the customer who pays for the new water sources, either through increased water rates or EA abstraction charges.