71.  In other word , they think fresh water is enough for us to use.

72.  Scientists have draw a conclusion from many facts that the average people's use fresh water is Decreasing.

73.  Thirdly, with the devolping of science, we can use water from sea that have been changed into fresh water or use the ice to restore the fresh water.

74.  We can find some methods to cut down the industrial use of water.

75.  The other hand, the population increases largely, so the fresh water is used increasely , adding the water of industry use, but our resource of water is limited, all these make the supply of water short and sense .

76.  This need to use advanted science.

77.  People always think fresh water won't be use up: Yes , the surface of the earth is covered by water of a large part , more than 70% and their are 97% of water in weight of the earth surface but the water is not the same as fresh water only 3% of the water is fresh water, the fresh water is in the rains, rivers and wells .

78.  People always think that there is plenty of fresh water for us to use.

79.  Is there enough water for us to use?

80.  But, in fact, fresh water is limited, it will run out, if we don't pay enough attention to the use of fresh water .