ABSTRACT
Our planet, the earth or gaia, is a water place. Water occupies 70% of the total earth’s area, about 360 10 12 m 2 , and the total water volume that covers the earth’s surface is about 1.40 10 18 m 3 . This makes the planet earth a very large water reservoir, nevertheless practically, these huge amounts of water are not directly usable, as 97% of this water is the seawater of the open seas and oceans and only 3% consist of fresh and brackish water, i.e., 0.042 10 18 m 3 . From these 3.0% fresh water reserves only a portion (0.014%) is in liquid form in rivers, lakes and wells directly available to us for immediate use, the rest can be found as glacier, icebergs and very deep water of geological reservoirs.
