Water: will there be enough?

UNESCO Courier, June, 1998 by France Bequette

For decades, experts have been making grim forecasts that the Earth will start running out of water and that conflicts over this precious liquid will erupt into wars. The situation is indeed alarming. In the first half of 1998, two international conferences on the world's water resources took place at UNESCO Headquarters in Paris. The theme of the first, organized by the French government and held in March, was Water and Sustainable Development. The second, in June, was jointly organized by UNESCO and the International Association of Hydrological Sciences and entitled "Water: A Looming Crisis?" Both events took stock of current knowledge, and participants discussed ways of coping with the problem.

How much water is there in the earth's reserves? Highly expensive probes have been sent to the moon, Mars and the satellites of Jupiter and Saturn to find out whether there is water on them, but we still lack accurate data about the earth's hydrological resources. Such information would help to provide a clearer picture of the future and, especially, to foresee the global repercussions of demographic and climate change.

One thing we know about water is that there is plenty of it. The total volume is put at 1.4 billion cubic kilometres - which could be imagined as a 2,650-metre-deep layer of liquid evenly distributed over the entire surface of the planet. But 98% of it is salt water, mainly in the oceans and seas. Most of the earth's fresh water is trapped in the polar ice caps. Less than 1% of it is available in lakes, rivers and shallow, easily-accessible aquifers. These water resources are constantly in flux. Water from the oceans and land evaporates into the atmosphere before falling again as rain or snow, nourishing plants and swelling rivers that flow into the sea. It also seeps through the ground and percolates down to aquifers. Very deep groundwater, known as fossil water, is impervious to seepage and not renewable.

In the industrialized countries, all you have to do is turn a tap and before you know where you are you've used a considerable amount of water - up to 600 litres per person a day in the United States. In hot developing countries, where shanty-towns on the edges of cities are crowded with growing numbers of migrants from the rural areas, a spigot and two litres of water a day are a luxury. "In the 1950s," says Mahmoud Abu-Zeid, president of the World Water Council, "only a few countries had this problem. But in the late 1990s, water is scarce in 26 countries where 300 million people live. Forecasts for 2050 indicate that 66 countries with approximately two-thirds of the world's population will experience a moderate to severe water shortage."

Over 1.3 billion people received improved drinking water services and some 750 million got better sanitation facilities during the International Drinking Water Supply and Sanitation Decade (1980-1990). But, says Mr. Abu-Zeid, approximately 1.2 billion people still have no access to drinking water and 2.9 billion lack sanitation. The resulting water-borne diseases take the lives of five million people a year, most of them children.

Farming and manufacturing account for most of the world's water consumption, far outdistancing human needs. Of the 3,240 [km.sup.3] of fresh water drawn every year, says the World Resources Institute, only 8% are used for human consumption. Each year fewer than ten countries use 60% of the world's 40,000 billion [m.sup.3] of surface and groundwater. Lastly, per capita consumption rises with the standard of living, ranging from 260 litres a day per person in Israel to 200 in Europe, 70 for a Palestinian on the West Bank and 30 in Africa.

THE DANGERS OF IRRIGATION

Demand runs highest in places where irrigation is indispensable, such as central Asia, Iraq, Iran, Pakistan, Madagascar and also in some industrially developed countries such as the United States. Farming accounts for two-thirds of the total water resources used by humans - a figure that rises to 80% in the Southern countries. Developing countries consume twice as much water per hectare of irrigated land as industrialized nations, yet their production is three times lower.

Because of the heat, half the water evaporates in storage areas (I [m.sup.3] per 8 [m.sup.3] at the Aswan dam in Egypt, for example) or when flowing through open-air irrigation canals. Poorly-conceived irrigation projects lead to deterioration of the soil, as French geographer and drought expert Monique Mainget demonstrates, using two examples.

The first is Pakistan. During the first half of the twentieth century, 10 million hectares were abundantly irrigated in the Indus plain. Waterlogging caused by irrigation, combined with a high rate of evaporation, has led to salinization of the soil, making it unproductive. The second example, the Aral Sea in the former Soviet Union, is different but the result is the same. Much of the water from the Syrdarya and Amu Darya rivers that flow into the huge lake has been diverted to feed 180,000 km of irrigation canals, only 12% of which have been made watertight. The rivers' flow is considerably restricted and the Aral Sea is drying up. "Irrigation for agricultural purposes is expensive," Ms. Mainguet says. "To make it profitable, farmers must use massive amounts of pesticides, herbicides and fertilizer on increasingly exhausted soil. The impact of pesticides on health has been overlooked. The child morbidity and mortality rates are among the world's highest."