Surplus and lack
The earth is a water-based planet. Some 70 percent of its surface is covered with water. The world water sources totals approx. 1.4 billion cubic kilometers. Hard to imagine. 97.5 percent of those water resources, however, are in the form of salt water and thus not directly usable as drinking water. A further two percent is tied up in glaciers and snow layers so that not even one percent of the total is available for direct human consumption.
110,000 cubic kilometers of rain fall each year on the earth’s land surface, albeit the volume available as freshwater world-wide is only 12,000 cubic kilometers owing to evaporation and a lack of access. Is this sufficient to supply humanity?
From 12,000 cubic kilometers of usable freshwater world-wide, some 4,000 cubic kilometers are actually used. The availability of water clearly exceeds the actual demand, thus at present on a global basis water is not scarce.
In principle there is enough water for everyone.
But freshwater is a regional resource. It is very unevenly distributed in the world. The various water flows are only connected globally in partial cycles, and as a consequence water management conditions differs greatly from region to region. Countries in the Middle East, where there is a shortage of water, do not benefit from the fact that Brazil and Canada have much more water than they can ever use. Likewise, it does not help people in the arid regions of Northeast Brazil that their fellow countrymen have more water available on average than most countries in the world.
Securing worldwide water supply is without doubt a global challenge. Yet the specific problems of water supply are usually tied to the regional situation and therefore need to be solved where they occur. In so doing there are various priorities which apply to an integrated water policy for industrial and developing countries. What is right for Nigeria may be wrong for Greece.