11.  They must not waste water any more.

12.  First, we should not waste fresh water.

13.  So, they think that it doesn't matter to waste some water.

14.  We must not waste water when we don't need it.

15.  First, we should not waste fresh water and use it in proper ways.

16.  It is necessary for government to educate people not to waste water.

17.  Many people have not concious of the importance of preserving our sourse of fresh water and many people are even wasting fresh water.

18.  First, we should enhance the consciousness of environmental protection, call for the public not to waste water.

19.  I think that we should not waste fresh water, and we should prevent factories from giving off wasted-water .

20.  Third, we should use water economically so that less water is wasted.