PIPE DREAMS?

Only one environment expert approached by the Sunday Herald believed Salmond's dream had a hope of becoming reality. In fact, George Fleming, an emeritus professor of engineering at Strathclyde University, believes the SNP is not going far enough.

"It is technically feasible to export water, but what is lacking is the political will," he said. The Government's Hydro Nation consultation was "unambitious", he argued. "It talks about what it might do, but doesn't say how to do it." Fleming believes pipes for transporting water south could be installed at the same time as building a high-speed rail link to southern England. And that a cleverly designed pipeline could generate hydro-electricity when it was flowing downhill to provide the power to pump it uphill.

He made a study in 1992 for Scottish Hydro Electric showing how large quantities of Scottish water could be moved south to England as part of a UK-wide water grid. It could also be exported by boat from existing harbours on the Clyde, the Forth, in Inverness and in Fort William.

"We will have to do this at some point in time on a global scale," he said. "What is needed in the future is a holistic approach to benefit Scotland's needs for water and energy while at the same time creating wealth through Scottish water exports."

But the idea of selling water to England has run into criticism from other experts, who warn that it would be impractical, polluting and horrendously expensive.

They point out that other solutions to the droughts afflicting southeast England would be much cheaper and easier. They include digging a new reservoir near London and transporting water from wet areas much closer than Scotland, like Northumbria, the Lake District or Wales.

Last week the Environment Agency warned parts of England were facing a drought this year. Seven water companies have announced hosepipe bans in the southeast from next month.

Interviewed by schoolchildren, Salmond suggested that Scotland could help alleviate the long-term shortages. It would be a "great thing" if Scotland became known as the "land of clean water", he argued.

"We are going to develop our water company so it can do things internationally," he said. "There might well be an argument at some time for the transportation of water resources. And because it costs to transport, you would sell it on that basis as an ongoing commercial transaction."

Scottish ministers have written to the coalition government in London offering to assist if water supplies run low. "We have massive resources, and we are willing to help put those resources to use, to help the southeast of England solve the strategic water shortage," said the Scottish Infrastructure Secretary, Alex Neil.

But that idea was branded "unrealistic" by Chris Spray, a professor at Dundee University's water centre and a former director of environmental science at the Scottish Environment Protection Agency (Sepa).

"The energy costs of moving water are phenomenal. I don't think it bears a lot of long-term thinking right now." It raised a series of difficult questions about ecological damage, costs and ownership, he argued.

"Ultimately, you don't want to move water to people, you want to move people to water," he said, adding that new housing should planned in areas rich in water.

Dr Sarah Hendry, another Dundee University specialist, said exporting water in bulk was "very problematic". It is heavy, and would have to be pumped over hills.

"The barriers are bigger than the advantages," she told the Sunday Herald. "We don't have a cheap and simple way of doing it. It's not like electricity and gas."

Hendry argued it was more important to cut down on the huge amount of water that is wasted. Exporting water would also mean that you would have to turn it into a commercial commodity, which would open up the difficult political issue of who should own and benefit from Scotland's water.

Scotland's water has no legal owner, though the Scottish Government has made clear that it wants to keep the company that supplies tap water and removes sewage, Scottish Water, in the public sector.

This, and many of the other issues raised by the Scottish Government's recent consultation, Hydro Nation, have been widely welcomed. But its suggestion that the "bulk export of water" could be "a practical solution for Scotland to offer" has raised hackles. Tommy Kane, who has been researching the Scottish water industry for five years at Strathclyde University, said moving water to the southeast of England would be a "monumental engineering effort".

The multi-billion pound investment needed would pose "fundamental problems" for the viability of such a project, he argued. "It does seem that the interventions by the First Minister and Alex Neil are hyperbolic and have not been thought through."

Environment groups are also aggravated by the suggestion. "The odd mercy dash with a water supertanker might be possible but any major transfer of water south would require a very expensive pipeline," said Dr Richard Dixon from WWF Scotland.

"Although the water shortages in the southeast are only going to get worse as climate change really bites, it still seems unlikely Scotland will be making money selling water to London," he said.

Lisa Webb, from the Royal Society for the Protection of Birds in Scotland, argued that diverting water from rivers or wetlands for farming could be "devastating". "Given the increased likelihood of droughts in the east of Scotland due to climate change and the considerable carbon emissions associated with transport of water, this proposal seems unsustainable and short-sighted," she said.

Climate forecasters have warned the east of Scotland to expect less rain, and the west to expect more. So it may become necessary to expand regional networks of pipes, canals and rivers to overcome local shortages.

Glasgow already gets a proportion of its water from Loch Katrine in the Trossachs, while much of Edinburgh's comes from lochs on the upper Tweed. But moving the liquid stuff hundreds of miles south is seen as an altogether different proposition.

"It is not simple," said Dr Jon Hargreaves, chief of Scottish Water for six years until 2007 and now chair of the British Waterways Scotland Group. "Ultimately, it depends on the market." He was not as sceptical as some of the prospects of Scotland developing an export business. But he accepted that the Kielder reservoir in Northumbria and the Lake District would be better placed to provide supplies to southeast England.

He also pointed out that it would cost maybe half a billion pounds to build a new reservoir in southern England, compared to the many billions that would be needed to build the infrastructure to transport water the length of the UK.

"It all depends on how desperate you are," he said. In the past water has been sent via road tankers in England to prevent Leeds going dry, and by sea tankers to Gibraltar when supplies from Spain were cut off.

The Scottish Government said Scottish Water could make a profit out of selling water to England.

"Water is an invaluable resource, and Scotland's ambitious scheme to develop as a Hydro Nation reflects the importance we put on it," said a Government spokesman.

Forget oil ... water is now what the world wants more than anything else

It is not just the southeast of England that is short of water. According to the latest United Nations (UN) water report, published last week, there are a billion people across the world who do not have access to safe drinking water, and the number is rising.

Droughts and water shortages are common across large parts of Asia, Africa and the Middle East. Two-thirds of the Arab region's available surface water originates from outside of the region, leading to many conflicts with upstream countries.

Experts have often predicted that "water wars" will break out in the Middle East as nations struggle to feed their people and water becomes scarcer. In his book, Peak Water, Scottish writer Alexander Bell imagines the decimation of Dubai, leaving hundreds of thousands dead.

"The great monument to 21st-century civilization lies in ruins, shattered into the sand like so many before," he wrote. "Not long before the world had fought over oil, but now water is the prize."

Bell, now a political adviser to the Scottish Government, also envisages water wars in less expected places. In one scenario, he has both Chicago and Toronto smashed into "twisted steel and broken concrete" after a war between the US and Canada over access to water.

Canada is one of the wettest countries in the world, but the US is growing short of water, partly because it consumes two and half times more per person than Europe. Debates have raged for decades over whether Canada should sell water to its southern neighbours.

The US problem is illustrated by Las Vegas. To sustain the city's two million people, water is brought 1400 miles from the Rockies by the Colorado River via a vast artificial lake created by the Hoover Dam. "This may be a sure case of ecocide," observed Bell. "Las Vegas can only die, and within our lifetimes, because the water supply is running out."

Even in Europe, as many as 120 million people lack access to safe drinking water. Another new report last week from the European Union's environment agency included a map showing the areas that are suffering the most.

Large parts of Spain, France, Ireland and the southeast of England are shown to have "extreme water stress". The whole of Italy and other parts of France, Spain and England are said to be enduring "water stress", while Scotland and other countries have "no stress".

"Water resources are under pressure in many parts of Europe, and it is getting worse," warned Jacqueline McGlade, the executive director of the European Environment Agency, based in Copenhagen. "With climate change making water supply less predictable, it is extremely important that Europe uses water more efficiently for the benefit of all its users. Water resources should be managed as effectively as any other natural asset owned by countries."

McGlade did not advocate moving large amounts of water around to combat the shortages. Instead, she urged new thinking on how to use less water along with "behavioural change".

Farmers, who use about a quarter of Europe's water, need to adopt less wasteful ways of watering their crops like "drip irrigation", she said. "Instead of just a hosepipe ban to fix this year's problem, you need to invest in a very different way."

At the UN World Water Forum in Marseille, France, last week the former Soviet president and Nobel Peace Prize laureate, Mikhail Gorbachev, warned there was no substitute for water. "The deficit of fresh water is becoming increasingly severe and large scale," he said. "Continuation of water consumption at 20th-century rates is no longer possible."

Irina Bokova, the director-general of the UN's Educational, Scientific and Cultural Organization (Unesco), called for a rethink: "Freshwater is not being used sustainably, according to needs and demands. The future is increasingly uncertain and risks are set to deepen."