Running dry - dwindling global water resources

Escalating consumption is threatening to outpace water supply

FOR decades, water has been wasted, mismanaged and overused--and the consequences are beginning to hit home.

Water scarcity typically conjures up visions of drought, the temporary dry spells that nature inflicts from time to time. But while droughts capture headlines and grab our attention, the far greater threat posed by our escalating water consumption goes largely unnoticed.

Signs of water stress abound. Water tables are falling, lakes are shrinking and wetlands are disappearing. Despite the disastrous experience of the years 1955 to 1985, engineers propose "solving" water problems by building ever more mammoth dams and river diversion schemes, with exorbitant price tags and damaging environmental effects. Around Beijing, New Delhi, Phoenix and other water-short cities, competition is brewing between city-dwellers and farmers who lay claim to the same limited supply. In the Middle East, water scarcity stirs up disputes and tensions that threaten to spill over into armed conflict.

In each major area of water use--agriculture, industry and cities--demand has increased rapidly, and because of improved living standards world water demand has been growing faster than population: at 800 cubic metres a year, per capita use today is nearly 50 per cent higher than it was in 1950. Global water use has more than tripled in the same period, and now stands at an estimated 4,340 cubic kilometres per year. But we actually rely on a far larger share since water bodies dilute pollution, generate electricity and support fisheries and wildlife.

Worldwide per capita water supplies, which drop as population grows, are a third lower now than in 1970. In an increasing number of countries, population has surpassed the level that can be sustained comfortably with the water available. Hydrologists designate water-stressed countries as those with annual supplies of 1,000-2,000 cubic metres per person. When the figure drops below 1,000 cubic metres, nations are considered waterscarce--that is, lack of water becomes a severe constraint on food production, economic development and protection of natural systems.

Today, discounting water flowing in from neighbouring countries, twenty-six countries, collectively home to 232 million people, fall into the water-scarce category. As many of them have very high population growth rates, their water problems are deepening fast. Africa has the largest number of water-scarce countries, but the Middle East is the most concentrated region of scarcity in the world, and tensions over water rights there could ignite during this decade.

Other parts of the world have not been spared. Symptoms of water stress exist, not just in the water-scarce countries, but in parts of water-wealthy ones as well. When groundwater is used faster than nature replenishes it, water tables fall and eventually the underground supply becomes too expensive to keep tapping and too salty to use. Overuse of groundwater is now endemic in parts of China, India, Mexico, Thailand, the western United States, North Africa and the Middle East.

FOSSIL GROUNDWATER DEPLETION

Some of the most troubling cases of unsustainable groundwater use involve "fossil" aquifers, underground reservoirs that hold water hundreds or thousands of years old and that receive little replenishment from rainfall today. Like oil reserves, these aquifers are essentially nonrenewable. Farms and cities that depend on this water will eventually face the problem of what to do when the wells run dry.

Saudi Arabia, for example, now mines fossil groundwater to meet 75 per cent of its water needs, and that dependence is growing as a result of government efforts to encourage large-scale wheat production in the desert. Though the country imports barley and other food crops, it became self-sufficient in wheat in 1984, and has since joined the ranks of the world's top wheat exporters. In early 1992, King Fahd authorized payments totalling $2.1 billion for 1991's record four-million-tonne wheat crop, which was worth only one fourth as much at the world market price.

Groundwater depletion in Saudi Arabia has been averaging about 5.2 billion cubic metres a year, and that rate is projected to increase by nearly half during the 1990s. At this rate the supply would be exhausted in fifty-two years. At the faster extraction rates projected for 2000-2010, it would dry up much sooner, and even before that happens the groundwater will likely become too salty to use without expensive treatment. Thus, little of Saudi Arabia's grain can be considered a reliable portion of the long-term food supply--either for Saudis or for those countries receiving its exports.

Other places dependent on fossil groundwater include Libya and the northwestern corner of Texas, where the amount of water in that state's portion of the Ogallala aquifer--the largest in the world--has already been diminished by a fourth. In Beijing, water tables have been dropping 1-2 metres a year, and a third of the wells have reportedly gone dry. Groundwater pumping in Mexico City exceeds recharge by 50-80 per cent, which has led to falling groundwater levels, aquifer compaction, and land subsidence that has caused the famous Metropolitan Cathedral to slump.

As demands continue to rise and water supply projects get more difficult to build, water budgets are becoming badly imbalanced in many regions. From southern California to Israel, from northern China to parts of India, shortages are becoming chronic and rationing a way of life. In China, for instance, planners project that Beijing's total water demand in 2000 could outstrip available supplies by 70 per cent. Israel's annual water use already exceeds its renewable supply by some 300 million cubic metres, or 15 per cent. With the projected influx of new immigrants in the coming decade, its yearly water deficit will worsen greatly.

DAMAGE TO THE AQUATIC ENVIRONMENT

Shrinking groundwater reserves, falling water tables and projected demands that far exceed available supplies are clear signals of water stress, but perhaps the most worrying sign of trouble comes from examining the health of aquatic environments. The damming, diverting and polluting of watercourses have wreaked havoc on the world's wetlands, deltas, lakes and riverine habitats. Of all imperilled biological species, aquatic fauna is undoubtedly at greatest risk.

The shrinking Aral Sea is but the most dramatic in a long list of natural areas destroyed, degraded or at grave risk from human use and abuse of water--a list that includes California's Mono Lake, south Florida's Everglades, Spain's Donana wetlands and Sudan's Sudd swamps, places that are home to astounding numbers and varieties of bird and wildlife species.

All these species are at risk from the degradation of the environment. In North America alone, the American Fisheries Society lists 364 species of fish as endangered, threatened or of special concern. An estimated one-third of the continent's fish, two-thirds of its crayfish and nearly three-quarters of its mussels are now "rare or imperilled".

A distressing conflict has emerged over two of water's roles: as a commodity, and as a key life-support for all species. This duality calls out for a fresh approach, one that pays greater respect to the vital functions of this precious element.

SANDRA POSTEL, of the United States, is vice-president for research at the Worldwatch Institute in Washington D.C., a non-profit research organization created to study and focus attention on world problems. She is the author of several Worldwatch papers, notably on global water issues.

COPYRIGHT 1993 UNESCO
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