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Two things show how important water is on earth. First, water is essential to life
survival. Second, the total amount of water in the world is constant and can neither be increased
or diminished, as it is true for wood or for coal, oil, etc.
All Water in the World
97%
3%
Seawater
Fresh Water
The total volume of water on earth is about 1,400 million cubic kilometers (1018 tones).
How many zeros that makes after the number 10?
10 _______________ tons
That is a lot of water!
However, more than 97% of this water is seawater.
How many cubic kilometers water is then seawater?
__________________________________
How many tones?
_________________________________________
How many % of water is not seawater?
_____________________________________
How many cubic kilometers are not seawater?
________________________________________
How many tons?
_____________________________________
World Fresh Water (3% of all water available)
Groundwater
22%
Snow & Ice
78%
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Of the percentage of water that is not seawater on Earth, 22% is groundwater, and 77% is ice,
locked in glaciers and ice caps.
How many cubic kilometers of water are available then for land usage?
____________________________________________________
How many tons?
_______________________________________________
So, less than 1% of fresh water is available for groundwater or surface water (actually 0.6%)
Less than 1% of Fresh Water is available
for Surface water, respectively:
3%
7%
33%
57%
Biologic
Atmosphere
Soil Moisture
Rivers & Lakes
Actually, of these 0.6% of surface water, 3% are found inside living creatures, 7% in the
atmosphere, 33% in soil moisture, 57% in rivers and lakes.
Even though, there is plenty of water for all our needs.
But surface water is unevenly distributed: some areas of the world are desertic or semi-arid while
others suffer from torrential rains and seasonal flooding. In fact, 15% of world’s largest rivers
carry one-third of the global runoff (roughly rivers of the Americas and Russia).
Problems:
Most of the surface water is used for agriculture, but 70 to 80% never reach the crops, so
there is much waste. Furthermore, the soil can become waterlogged and salinized in the process
because of men’s ignorance of the nature of their soil.
Even if industry does not use much water, it pollutes much more since water is needed for cooling
and cleaning. Actually 80% of the water is being returned to its source, if not polluted, at least
hot (in the case of nuclear power pants) which can disturb significantly the natural environment
of rivers and lakes.
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