A Thirsty WorldThe world is not only hungry, it is also thirsty for water. This may seem strange to you, since nearly 75% of the earth's suce is covered with water. But about 97% of this huge amount is sea-water, or salt water. Man can only drink and use the other 3%-the fresh 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 (冰山) and glaciers (冰川). Even worse, some of it has been polluted.