The essential about water on Earth
How much water is there on Earth ?
On Earth there are about 1 400 000 000 000 000 000 000 liters
This amount may seem very high nevertheless water exists under various
forms and states and only a small percentage of it can be useful for
Percentage of water on the Earth
sources of water
70% of the surface of the Earth (almost three quarters) is
covered by water (seas, oceans, lakes, rivers). This
makes of water the most important material on the surface of Earth and
justifies the expression " Blue planet " used to called the Earth.
Earth is the only known planet ( so far ) whose surface is partially
covered with liquid water .
water on Earth, view from space. Photo courtesy of
US Fish & Wildlife Service Photo
All available water resources on Earth are also called "
Mains sources of water are:
- Seas and Oceans
- The waterways (rivers, streams)
- The underground reserves
- Ices (glaciers, sea ice, icebergs, snow)
- Various forms of water present in air (clouds, water vapor).
Fresh water and salt water
There are two kinds of water:
- Salt water (97.2%) present in the seas and oceans.
- Fresh water (2.8%), that is to say water that does not contain salt,
in lakes, streams, groundwater, ice and in the atmosphere.
To survive man needs fresh water but it is rare compared to salt water.
The fresh water reserves are very precious and must be protected.
- Can be drunk by humans and animals (as opposed to salt water).
- Can be used for irrigation in agriculture (most plants can't tolerate
- Can be used for washing (salt water partially neutralizes the effects
of soap and leaves some salt on the skin as it dries)
water on Earth
water must not be mistaken with drinkable water. Fresh water can
be consumed without danger for health only if it doesn't contain
bacteria, virus or pollution.
: official website of Fairfax
that provides water to roughly 2 millions people in Virginia.
website offers educational resources about water for kids and teachers
: This page provides acurates
data and percentage about sources of water.
National geographic kids networks gives free access to educational
resources based on standard science curriculum. This page is about
percentage of water on Earth, drinkable water and water cycle.