WATER is an essential "common good" that until fairly recently was thought to be superabundant, and therefore used wastefully, especially in the wealthy industrialized nations.
But in reality water is a relatively scarce resource: extremely scarce in some parts of the world. And as the world's population grows and its standard of living gradually rises, the demand for water, and therefore its cost, is bound to increase.
Taking into account possible climate changes, the already-difficult water problem can only get more complicated. Since every increase of 1 degree centigrade in average temperature moves the temperate latitudes 100 or 200 kilometers (62 to 125 miles) farther away from the equator, the areas where farm productivity is now highest could eventually become semiarid or arid, with drastic consequences for world food production.
Of course, large-scale projects will always be needed to transport fresh water from places where it abounds to places where it does not. In addition, cost-effective ways must be found to exploit new water resources: by desalinating seawater, for instance, and purifying polluted water. But more to the point are small-scale actions that, with relatively small investment, can promote conservation of this precious resource.
Sound water management starts with land-use and watershed management. Drainage must be designed to collect runoff, especially from torrential rains that lead to erosion and landslides. The creation of adequate vegetation cover, irrigation systems, and small interlinking ponds makes it possible to store water against dry seasons and prevent erosion.
Another aspect is the modernization of water treatment, recycling wherever possible and always aiming to prevent waste. Cascade use must be properly managed: in geographical terms, from higher to lower localities; in pollution terms, from lesser to more contaminating uses; in terms of priorities, taking adequate account of each country's typical needs, from domestic uses to farming, power generation, and industry. A `software' approach
Accordingly, water-management strategies need to take a "software" approach, emphasizing the intangible and system organization. This implies a complex process made up of many different steps, relatively inexpensive and simple enough in themselves, but conceived as parts of a whole system and implemented from the bottom up. Naturally, large projects and costly solutions will still be needed where "soft" actions do not suffice.
Today, agriculture accounts for around two-thirds of all the water consumed worldwide. With the population growing steadily, it would be unthinkable to try to limit world food production or farm productivity. Irrigation, together with fertilizers and pesticides, is the principal means of increasing farm productivity, and in the past few decades it has been instrumental in fighting hunger in the third world, especially in Asia.
In 1900, 40 million hectares (99 million acres) of the world's farmlands were irrigated. By 1950 the figure had grown to 95 million hectares (235 million acres); by 1980 it was more than 200 million (494 million acres). During the 1980s the expansion of irrigation slowed, in some cases because of the appearance of symptoms of aquifer depletion, and in others due to the shelving of new irrigation projects that lost out to industry and cities in the growing competition for scarce water resources.
Water availability is a particularly dramatic problem in many parts of Africa, where the combination of an arid climate, drought, soil depletion, and deforestation has aggravated the malnutrition of an exploding population. Here, as elsewhere, the problem must be thought through in new terms that take account of the complex interaction among the factors of food, water, land conservation, and preservation of genetic diversity.
Irrigation systems can be redesigned to give plants exactly the amount of water they need, without flooding the ground. The ultimate technology today consists of computerized drip irrigation, using underground humidity detectors to reduce water inputs to the minimum required for optimal production.
Plant geneticists are developing less-water-demanding crop strains; for instance, rice cultivars that need not be submerged in water (though it acts as a thermostat against excessive cold and heat). Plants that tolerate brackish water are also being developed, though in this case one should contemplate crop rotation, which is essential to prevent soil depletion.
Other important aspects are the replacement of chemical pesticides with biological pest-control techniques, and the application of fertilizer directly to plant roots, which reduces water pollution and the oxygen-starvation of lakes. Saving water in industry
Industrial water requirements can also be rationalized. Enormous amounts are consumed, and heavily polluted, by paper mills, tanneries, and many processes in the chemical, textile, and hydrometallurgical industries. But it is proving increasingly feasible to design solutions that require much less water. Now paper mills, textile factories, and tanneries consume many times less water, and contaminate it less, than even their very-recent predecessors.
The two fundamental aspects which should be provided for in all industrial activities are the purification of waste water to make it suitable for other uses (the quality of treated water is determined to a great extent by purification costs) and the creation of closed cycles, whereby waste water is recycled in the industrial process itself. In this connection, many suggestions can be gleaned by studying the membranes and biochemical processes that purify and regulate water flow in living organisms, inclu ding human beings.
Lastly, numerous steps can be taken to rationalize our household and sanitary uses of water, for instance by installing alternate-action toilet tanks, or water taps that turn on only when a person's hands are underneath them. The main issue is to educate the public and adopt water-conservation policies; that is, "soft" steps that can also work through the market by turning water into a long-term strategic factor.
The price of water must increasingly reflect its scarcity and the real costs of its supply. Higher rates may be more acceptable if part of the increase is used to pay for investments aimed at limiting consumption.
In conclusion, important opportunities are opening up for wide-ranging actions that require no earthshaking decisions or mammoth invest- ments, but that comprise an organized and integrated package of often-intangible initiatives that involve participation by individual citizens. This is a promising path that should guide future strategies for managing water resources.