8. Pressure mounts around scarce water resources

Water stress increases; better management needed

Paradoxically, water is a renewable resource and yet millions of people are denied access to this most basic of needs. The problem is not one of quantity, but rather of the way water is distributed and used.

It is estimated that more than a billion people have no clean drinking water. Asia and sub-Saharan Africa are the regions where the shortage is most severe.

The United Nations warned in 1997 that if current trends continue, two-thirds of the world's population will suffer moderate to severe "water stress" by 2025.

The problem has worsened in the 10 years since Rio as populations have risen, agriculture has become more intensive and urbanization has pushed up the demand for clean water. In many places, extraction is taking place at an unsustainable rate. Water tables are falling in major grain-producing areas like the North China Plain, the Punjab in India and the Great Plains of the United States.

The common response to the problem, namely sinking deeper boreholes, typically delivers only a short-lived respite. At the same time, it causes older, shallower wells to dry up.

"Despite water shortages, misuse of water is widespread and farmers use large amounts of water poorly," reported a recent study by the International Programme for Technology and Research in Irrigation and Drainage.

Water shortages are closely linked to food shortages. It takes around 1,000 tonnes of water to raise a tonne of grain. Without adequate water for growing crops, people in developing countries go hungry. According to Robin Clarke, author of "Water: The International Crisis," water shortages were behind Africa's catastrophic famines of the 1970s and 1980s. "The real truth was that Africa was short not so much of food as of water," he writes. "If better means of conserving and using the water we have are not found, development will remain slow in many of the poorest areas of the world for decades, possibly centuries."

Developing countries whose demand for water exceeds the supply are faced with an impossible choice: make do with even less, or resort to using untreated water. The former leads to famine; the latter to disease. According to Joanne Green of the Water Matters campaign, a child dies every 15 seconds from a waterborne disease.

Because rivers and aquifers frequently cross national boundaries, tensions between neighbouring states over water are commonplace. A decision to divert water away from a river--into an irrigation network, for example--can have dire consequences downstream.

The list of disputed waterways is extensive. The Jordan, the Nile, the Zambeze, the Rio Grande and even the Danube all are the subject of heated argument between neighbouring countries.

Although water is a renewable resource, the debate over how best to manage and distribute it mirrors that over fossil fuels and electricity. As with energy, demand for water is rising. During the last 50 years, consumption has quadrupled. And just as energy efficiency measures can offset the need to build large fossil-fuelled power plants, so water conservation policies can take the place of large, ecologically intrusive infrastructure projects.

For example, experiments with drip irrigation in Jordan demonstrated water savings of 20 to 50 per cent compared with conventional spray irrigation.

Through better management and fairer distribution, the goal of providing every human being with access to clean water is achievable. Yet until it is given the priority it deserves, sustainable development will remain a remote prospect.