Already just over a quarter of the Earth's population face a struggle to obtain enough water to drink, grow food and run industry, say the documents. ``By 2025, as much as two-thirds of the world population would be under stress conditions.''
Total water consumption world-wide has been growing at 2.5 per cent a year, roughly twice as fast as population growth. It has risen sixfold this century. In 30 years' time, 27 nations, all but three of them in North Africa, the Middle East and South Asia, are forecast to be in the UN's ``high water stress'' category; these include India and Pakistan.
They will face ``serious scarcity'', with ``an urgent need for intensive management of supply and demand''. Water shortages will act as a brake on their economic growth.
One solution, argue both reports, is for water supply to be devolved from big government - often responsible for disastrous damming and irrigation schemes - to local communities and private industry. The other is to concentrate on restraining demand and using the resource less wastefully.
The two reports, written as a follow up to the 1992 Rio Earth Summit, say that water shortages are as urgent as any other global environmental issue.
With some 300 major river basins crossing national boundaries ``future conflicts [over their water] are a potent risk''. Among the most likely flashpoints are thought to be the river Jordan, whose waters are shared between Israel and Arab neighbours, the Nile, which flows through Ethiopia, Sudan and Egypt, and the headwaters of the Euphrates and Tigris shared between Turkey, Syria and Iraq.
A growing number of countries, including India, China, Mexico, the US and some southern ex-USSR republics, are now taking water from aquifers at a much faster rate than they can ever be replenished by rain. As a result water tables have sunk. In some countries, such as Libya, farming and industry have come to depend on underground ``fossil'' water, which comes from rain which fell thousands of years ago. Once ``mined'' it can never be replaced.
The reports point out that desalinisation plants, which take the salt out of seawater, are expensive to build and run and are only an option for wealthy nations such as Saudi Arabia.
The populations judged most at risk are those in poor countries (defined as having a per capita annual gross national product of less than $2,895 [pounds 1,733]) subject to high water stress. There are 1.5 billion people in that category. Their communities will struggle to find the money needed to deal with worsening shortages as their population and water demand rise.
Egypt is the classic example of a country which is in real danger of a water disaster, say the experts. It is poor, has a rapidly growing population and is almost entirely reliant on the Nile for its water.
Egypt is already a heavy importer of basic foodstuffs, while water-hungry cotton is the most important cash crop. The state buys up all the cotton, but it supplies irrigation water to farmers at a heavily subsidised price. Such subsidies, say UN insiders, guarantee the water is used wastefully. But they are found not just in Egypt but in many countries which use extensive irrigation, including the US.
Farming consumes most of the water used by humanity, with increases in irrigation largely responsible for the huge increases in crop production needed to feed a fast-growing population. As a result, many great rivers no longer reach the sea, and wildlife-rich swamplands have dried out.Reuse content