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  Yahoo News 22 Mar 07
Water scarcity: Global warming to deepen thirst for blue gold
by Richard Ingham and Anne Chaon

PARIS (AFP) - Fresh water, the stuff of life, is set to become even more precious as global warming begins to bite, experts warned ahead of World Water Day on Thursday. The theme of this year's event is watser scarcity, a problem familiarly driven by population explosion, chronic wastage and pollution.

The UN estimates that, by 2025, two-thirds of the planet's population will be living with water stress, with North Africa, the Middle East and West Asia the worst-afflicted regions.

But global warming is bound to accentuate the scarcity, say experts. In many regions, greater aridity, shifting rainfall patterns and dwindling runoff from snow and ice in mountains may badly deplete rivers, lakes and aquifers.

In contrast, other regions will get more rainfall -- but this may take the form of fierce rainstorms that cause flash floods rather than a useful drizzle that soaks into the ground. Or the precious stuff may fall in areas that are sparsely populated or where there is no infrastructure for capturing and storing it for use during dry spells.

Scientists in the UN's Intergovernmental Panel on Climate Change (IPCC) are due to highlight the phenomenon in a report, due to be released in Brussels on April 6.

It is the second volume in a long-awaited assessment on global warming. In higher latitudes and some wet tropics, including populous areas of East and Southeast Asia, water availability is "very likely" to increase over this century, according to the latest draft of the report, seen by AFP.

But countries in the mid-latitudes and dry tropics, which are already water-stressed, would have less water. "Drought-affected areas will likely increase and extreme precipitation events, which are likely to increase in frequency and intensity, will augment flood risk," according to the document, which is still being finalised.

It adds: "Water volumes stored in glaciers and snow cover are very likely to to decline, reducing summer and autumn flows in regions where more than one-sixth of the world population currently live."

In global terms, a temperature rise of 2 C (3.8 F) by 2100 compared with 1990 levels -- towards the lower end of the IPCC's estimates of the likely warming -- would place up to two billion in a position of "increased water scarcity." A rise of 4 C (7.2 F) would bring the tally to as many as 3.2 billion people, the draft calculates.

Africa and Asia would be the two worst-affected continents. But rich countries, which have more money, technical resources and expertise, also face the problems of water stress. From the fast-growing "sun belt" states of the southwestern United States to southeastern Australia, where water is extracted from depleted rivers or ancient aquifers are run down for lawns, golf courses and swimming pools, climate change could also mean a wrenching change in lifestyle.

In February, the European Environment Agency urged European governments to start planning now to cope with climate-induced water stress, and singled out southern Spain, southern Italy, Greece and Turkey as being badly exposed.

Reservoirs and use of ground water stocks are designed for a relatively long "recharge" season of rain or runoff from melting snow. If the recharge season is short, or it provides so much rain in one go that the ground surface saturates and the water infiltrates, the result is flooding and later scarcity.
links
World Water Day website: 'Coping with Water Scarcity' is the theme for World Water Day 2007, which is celebrated each year on 22 March.

Related articles on Global: general issues and Global issues: Climate change
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