Global Shortage of Fresh Water 全球淡水短缺
1、人们以为淡水是取之不尽的 （提示：雨水、河水、井水……） ；
It is widely thought and accepted that the world's supply of fresh water will never be run out of （used up） because it comes from such a variety of sources as rain ,river, well. Such an opinion leads to a shocking waste of water.
However （As a matter of fact）， the earth is short of fresh water. There are many causes for the shortage of it. First, the word's population is growing rapidly. Second, The demand for water is rising. What's more, our surroundings has suffered serious pollution. All of the reasons mentioned result in the urgent need of fresh water, especially in some big cities.
Therefore, measures should be taken to deal with the problem. To begin with, strict laws should be passed to control any waste of water. Second, the sense of saving water should be educated among people. Above all, scientists must work even harder to purify the sea water and polluted water.