1.  And pullotion of the water have reduced the water available greatly.

2.  The most important factor must be that we have polluted the water resource so seriously that there is less fresh water available today.

3.  On the one hand, with the increasement of porpulation and the advancement of modern industry, more and more fresh water is needed, on the other hand, the water pollution is so serious that the available fresh water is Decreasing, which results in the shortage of fresh water.

4.  On one hand, there isn't so much fresh water available on the Earth , as people had thought about .

5.  Thought there is a lot of water on the earth, the available water is small for the quantity.

6.  Since, population increases, fresh water for industry adds and a lot of rivers is polluted by industry, the available fresh water is rare.