跨國地下水資源長期受忽視 聯合國擬訂新公約保護

Underground aquifers contain 100 times the volume of fresh water found on the Earth's surface but they have been neglected under international law despite their environmental, social, economic and strategic importance.

On Monday, that will change as the UN General Assembly receives the draft of a new international treaty to safeguard these enormous pools of underground water shared by more than one country.

The draft Convention on Transboundary Aquifers applies to 96 percent of the planet's freshwater resources - those that are to be found in underground aquifers, most of which straddle national boundaries.

Many shared aquifers are under environmental threats caused by climate change, growing population pressure, over-exploitation, and human induced water pollution.

The draft treaty requires that aquifer states not harm existing aquifers and cooperate to prevent and control their pollution. Prepared over the past six years by the UN International Law Commission with the assistance of experts from UNESCO's International Hydrological Programme, the treaty is intended to fill a gap in the law.

To accompany the draft treaty, UNESCO is publishing the first-ever world map of shared aquifers. It shows the aquifer locations and provides information about the quality of their water and rate of replenishment by rainfall.

So far, the inventory includes 273 shared aquifers - 68 are in the Americas, 38 in Africa, 65 in eastern Europe, 90 in western Europe and 12 in Asia.

The growth in the demand for water since 1950 has been met by the increased use of underground resources. Globally, 65 percent of this water is devoted to irrigation, 25 percent to the supply of drinking water and 10 percent to industry.

Underground aquifers account for more than 70 percent of the water used in the European Union, and are often the only source of supply in arid and semi-arid zones.

Aquifers supply 100 percent of the water used in Saudi Arabia and Malta, 95 percent in Tunisia and 75 percent in Morocco.

Irrigation systems in many countries depend very largely on groundwater resources - 90 percent in the Libya, 89 percent in India, 84 percent in South Africa and 80 percent in Spain.

One of the largest aquifers in the world is the Guarani Aquifer, extending over 1.2 million square kilometers, shared by Brazil, Argentina, Paraguay and Uruguay.

Although aquifer systems exist in all continents, not all of them are fed on a regular basis by rainfall. Those in north Africa and the Arabian peninsula were formed more than 10,000 years ago when the climate was more humid and are no longer replenished.

In some regions, even if the aquifers are renewable, they may be endangered by over-exploitation or pollution. In the small islands and coastal zones of the Mediterranean, people often use groundwater more rapidly than it is replenished.

The aquifers in Africa, which are some of the biggest in the world, are still under-exploited, the UN agency says, adding, "They have considerable potential, provided that their resources are managed on a sustainable basis."

Since they generally extend across several national boundaries, the sustainable use of African aquifers depends on agreed management mechanisms that will help prevent pollution or over-exploitation.

In their project concerning the Iullemeden aquifer that extends over 500000 square kilometers in the semi-arid tropical savanna ecoregion of West Africa, Niger, Nigeria and Mali have approved in principle a consultative mechanism for administering the aquifer system. UNESCO says such mechanisms still are rare but the new treaty may encourage their formation.