ONE PLANET … ONE WATER CYCLE …
Water is present everywhere on earth and is indispensable for life.
Astronauts who have been lucky enough to observe our planet from space come back fascinated by its
The quantity of water has remained unchanged for 4.4 billion years, and is distributed between four major sources :
incredible beauty and its amazing blue colour. This colour, which has earned Earth its nickname of the
oceans, coastal waters, the atmosphere and biosphere.
“blue planet”, is partly linked to the vast expanses of water that cover it.
On average a molecule of water
remains in the atmosphere for 8 days
Atmosphere
Precipitation before falling back to the ground.
0,001 %
billion
Condensation
Storage
The volume of water on Earth amounts to
1.385 billion km3. If it were to be spread in depressions
out evenly over the surface of the globe, it
(lakes, ponds, etc.)
would form a layer 2.7 km thick.
Run-off
The oceans cover 71% of
the Earth’s surface. It’s the
A molecule of water remains for a few
blue planet.
hours only in the cell of a plant or ani-
mal.
Evaporation
Plants and animals
0,0001 %
Large and small rivers
Salt water accounts for 97.2%
0,0001 %
of water on Earth, with fresh In soils
Lakes
water only accounting for 2.8% 0,005 %
0,01 %
Water is an asset that is poorly
shared out on Earth. 40% of the
world’s population lack water.
The water available to
Infiltration
mankind on Earth repre-
On average a drop of
sents less than 1% of the
water remains in a Oceans
total volume.
river for 2 weeks
65% of an adult human’s body 97,2 %
and in a lake for 17
is made up of water.
years.
Glaciers and polar ice caps
2,2 %
Subterranean water
Renauld
sources
0,6 %
In the glaciers and polar ice caps, water
One kilogram of sea
On average a drop of water remains is sometimes stored for up to 10,000 years.
water contains on
in the seas and oceans for 2,500
average 34.4 g of salt.
years.
Underground discharge
… AND MANY
Key
Bacteriological pollution Waste pollution
Nitrate and phosphate pollution
Hydrocarbon pollution Physical-chemical pollution
TYPES OF
POLLUTION!
Water is the preferred vehicle for all types of
pollution. Watercourses, rivers, then streams
sweep the poison along for miles before pouring
it out into the ocean.