The world is not only hungry it is also thirsty for water. This may seem strange to you since nearly 75% of the earth's surface is 31 with water. But about 97% of this huge amount is seawater, or salty water. Man can only drink and use the other 3%-the 32 water that comes from rivers, lakes, underground, and other sources. And we cannot even use all of that, because some of it is in the form of icebergs and glaciers. Even 33 , some of it has been polluted.