Sea and Space / Water

## Water for human beings

### A historical approach

#### Mythology: the Ocean

A long, long time ago, the Earth was presumed to be a flat disk surrounded by a river, Oceanus, the oldest of the Titans. Beyond it lay Hell and the Land of Dreams. Oceanus was the consort of Tethys (the goddess of water), father of all the rivers and the three thousand or more river gods.

Water has always fascinated Man. Long ago, our forefathers reasoned that, since they first appeared in the primitive oceans, living beings must be part of the "water cycle". Indeed, water was crucial to their existence and way of life; it was the main component of their bodies and their main source of food.

For Thales of Miletus, the first of the Ionian physiologists, water was the principal element on which everything else was based. Following him, Empodocles of Agrigento established the four elements: air, water, earth and fire. He called them the four "roots".

In Thales' time, people believed that all material came from water: air by evaporation, land by a kind of condensation, and even fire by heating water. But it was above all Plato, the famous Greek philosopher, who developed the theory of the four Empodoclean elements. In one of his "dialogues", known as "Timaeus", he gives each of these bodies a specific geometrical form: fire is represented by a regular tetrahedron, earth by a cube, air by a regular octahedron, and water by a regular icosahedron.

To this theory based on symmetry, Aristotle added "ether" which was supposed to fill interstellar space and from which the stars were formed. The properties of Plato's four bodies were derived from the properties of the corresponding polyhedron that covered the surface as a whole. One of their most remarkable properties was the ability of three of the elements (excluding earth) to be transformed into another form. This transformation was determined by discrete (non-continuous) laws. By contrast, mixtures of the four bodies could contain variable proportions of fire, air, water and earth. These were the famous compounds or "mixtions" that were taken over by the learned people during the European Middle Age and the Renaissance.

Fertility was the primordial sense given to water, and it was also in this element that the sexes were thought to interact. At one time, it was confounded with sperma by the Sumerians (who used the same hieroglyph for the two concepts). For other people, it was the primordial Mother, as for instance the ancient Mexicans and the Teutonic tribes in central Europe.

Baths and rejuvenating drinks have been considered important medical treatments since the most ancient of times. This tradition continuous at the spas with hot spring baths in Japan and Europe where modern medical science has now replaced the ancient myths and legends.

Water, experienced either as a drink or in a bath or by total immersion, is effectively a continuation of the ancient, highly symbolic water rites that were linked to fertility. What was originally achieved by the primordial waters, can today be achieved under particular circumstances where water or another liquid will once again provide strength, fertility, good health, and long life to those who use it correctly.

But water has also been seen as the Great Flood that was both a cataclysmic revenge and the purifying end to the corrupt world of mankind. Comparisons of the ancient scriptures have clearly shown the universality of myths about a "flood", from the Semitic tribes to the people of the Pacific, from Atlantis to the legends of the Andes. They all refer to a world engulfed by water, thus determining the future of Mankind.

### Water on the Earth

The Mediterranean Sea - courtesy NOAA

Water is so familiar in our daily life that we often forget its importance and uniqueness. It owes the extremely important role it plays on the surface of the Earth to its very specific physico-chemical characteristics. This concerns not only the biosphere (of licving beings), but also the lithosphere (the solid Earth) the surface of which it modifies all the time. Without water, there is little doubt that the Earth would be just another dead celestial object. Its surface would look much like that of the Moon, with craters and a lot of dust.

Water is a universal solvent in the biosphere. It is an essential part of all biochemical reactions. It is a major constituent, not only of the environment that surrounds all living aquatic and terrestrial organisms, but also their inner parts. Living cells are made of aquatic solutions, suspensions and emulsions with water present from about 70% by weight (in ossified or mineralised tissue) to 98 % (in aqueous fruit, jellyfish). The youngest, most vigorous, and most active tissues are generally those with the highest water content.

Plants for the most part take the water and mineral salts they need from the soil. Water in liquid form comprises from 50% to 75% of plants by weight, and 70% of the human body. It is intimately involved in the functional systems, and it takes part in the decomposition of a number of substances such as sugars. In general, natural water contains mineral and organic impurities, and nearly always dissolved gases (air and carbon dioxide - CO2).

This image shows the Aral Sea in Central Asia. It one of the greatest, recent ecological catastrophes. Due to a too intensive agricultural use of the water in the rivers that used to feed this lake, the water level has dropped about 15 metres since the 1960s, - leaving huge salt sheets behind. Photo obtained from the Space Shuttle. Courtesy - NASA.

There are various problems connected with the abundance of water that are at present far from being resolved. As a natural resource it has become the major concern of a great many countries, and not only those in arid regions. All over the world, water is getting sparser and European countries are continously looking for new sources of drinking water. The industry requires a large amount of water for the manufacturing processes, as so does agriculture. The rapidly increasing human population needs water for domestic purposes and to generate energy.

In fact, all countries are concerned, and it is symptomatic in this respect that the overall average consumption of water per head is considered a good indication of a country's level of economic development, given its high correlation with the country's Gross National Product (GNP). Desalination of sea water, at present very costly, is only used in extreme cases (arid but otherwise wealthy countries), but may play a larger role in the future.

On the other hand, water has always been a source of danger for man who is often defenseless in the face of large-scale hydrological phenomena: high tides, tidal waves, devastating rains.

Water also spreads waste materials and poisonous substances that Man manufactures in ever-increasing quantities.

These aspects, amongst others, more than justify the number of sciences that study water in all its different forms, in particular: oceanography, glaciology, hydrogeology and limnology, both part of hydrology, natural water science, and hydrodynamics and hydraulics, both concerned with the equilibrium and transport of water in liquid state.

Did you know that:

- Agriculture alone consumes 70% of our fresh water resources; industry and power generation some 22%. Only 8% is used for human consumption and in human health.
- Some 1.5 billion people do not have access to wholesome water.
- Some 50% of the world's population do not have adequate water purification systems. More than 30 million people die every year from diseases linked to polluted water (cholera, malaria, hepatitis, ...)

Try your skills on these exercises:

- On the map of the world, find the countries and regions most threatened by "hydrological stress" (lack of water, polluted water)
- Use satellite images to detect the high water mark of particular rivers and the vast areas flooded.