According to a UNESCO expert, water could soon be more coveted than oil. Indeed, access to freshwater could very well become the major issue of the 21st century. At present, one out of five people, or more than one billion human beings, do not have access to drinking water. And by the middle of this century, between 2 and 7 billion people in 48 to 60 countries will be water-scarce, according to the United Nations.

Although water is the most widely occurring substance on earth, only 2,5% is freshwater while the remainder is salt water. And the amount of water available is finite; although water does not disappear, new water is not created. At the same time, demand is rising on all continents.

The water cycle follows a set pattern. Water evaporates from oceans, lakes, rivers and streams, condenses in clouds and then returns to the surface in liquid form as rain, snow or hail. Part of this rainwater evaporates, part soaks into the ground and the rest runs off into rivers and streams. Eventually, the groundwater also drains into rivers and streams, which flow into the oceans so the cycle can begin all over again.

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