Ireland has plenty of fresh water but no oil: the Middle East has little water but plenty of oil. During the 1970s oil crisis a proposal was made in Dail Eireann that Ireland could circumvent the problem by sending tankers of water to the Middle East in exchange for tankers of oil.
Water is the most precious liquid on Earth and is essential for all living things. Quantitatively it constitutes the greater part of our bodily bulk. If you weigh 12 stone, water accounts for nine of these.
Biological life consists of two phases, solid and liquid. Water is ideally suited to form the liquid phase, just as carbon is ideally suited as the element on which all the other chemical compounds in the body are based.
Two-thirds of the Earth's surface is covered with water, but most of this is salty and cannot be used directly for human or agricultural nourishment. Only 2.5 per cent of water on Earth is fresh, and two-thirds of that is locked into ice caps and glaciers. Less than one -hundredth of 1 per cent of Earth's water is both drinkable and renewed each year by rainfall and other precipitation.
The world's renewable freshwater supply has remained unchanged since civilisation began, but human population has greatly increased. Therefore the amount of water available to each person on Earth is steadily declining. It has dropped by 58 per cent since 1950 as the world population rose from 2.5 to six billion. It will drop an additional 33 per cent if world population reaches the projected nine billion by 2050.
In many countries freshwater supplies are awkward to adapt to human needs. For example, rainfall and river flow are not distributed evenly throughout the year. Many rivers run highest when water is needed least, and two-thirds of the world's river water each year rushes unused to the sea in floods. Monsoons in many developing countries bring 75 per cent of the annual rainfall in just three months.
Water management is largely the capture and delivery of water to cities and farms where it is needed most. Irrigated land area has increased 30-fold over the last 200 years. Near-desert areas, e.g. in Egypt, have been transformed into fertile gardens. Large cities have grown on artificial oases, e.g. Phoenix, Arizona.
While the affluent world gambols in desert swimming pools, many women in sub-Saharan Africa walk miles daily in order to bring water to their families. More than one billion people in the developing world have no safe supply of drinking water, and 2.8 billion lack minimum sanitation facilities.
About eight million deaths occur each year from water-related diseases such as cholera. Millions of poor farmers worldwide cannot afford to irrigate their lands, leading to poor crop yields and complete vulnerability to droughts.
But even parts of the world that are relatively well endowed with freshwater and other resources are starting to experience water problems. Much of the world's stable year-round water supplies comes from underground geological formations called aquifers.
Most aquifers are replenished by rainwater seeping through the ground, but water is being drawn from aquifers faster than it is being replenished in several of the world's great food-producing areas, e.g. southern California; the southern Great Plains in the US; India; and China. This places a threat today over 10 per cent of global food supply.
Competition for water is increasing both within and between states. The urban population of the world is expected to double to five billion by 2025, which will add pressure to divert water away from agriculture.
About 260 rivers in the world run through two or more countries, and in most cases no treaties regulate how the water should be shared.
Tension is developing in several regions, e.g. in the Nile basin. Egypt is the last in line to receive Nile water, 85 per cent of which originates in Ethiopia. Ethiopia has used little of the water to date, but is now building small dams. Egypt is building large irrigation projects, which puts it on a collision course with Ethiopia. Middle Eastern wars in the future may well be over water, not oil.
Diverting water for agriculture and cities has depleted water in many natural ecosystems, damaging or destroying them entirely. For example, the once mighty inland Aral Sea in Russia has decreased in volume by two-thirds and in surface area by half after 35 years of siphoning off water. Now winds blow toxic salt-dust from the exposed seabed on to surrounding crops and villages.
More efficient ways of irrigating crops must be developed and implemented.
Drip-irrigation offers great potential. This is a system of perforated pipes on or below soil level that delivers low-volume water directly to plant roots. It delivers 95 per cent of its water to roots compared with 60 per cent by conventional methods, it cuts water use by 50 per cent and boosts crop yields.
Finally, it is scandalous that so many people worldwide have no secure water supplies and no sanitation facilities. It would cost about $50 billion per year to provide universal access to water and sanitation, which is 7 per cent of global military expenditure.
Much of the information in this article is based on a paper by Sandra Postel in The Sciences (March/April 2000).
William Reville is a senior lecturer in bio- chemistry and director of microscopy at UCC