| The water
cycle is the process by which water travels from the Earth's
surface to the atmosphere
and then back to the ground again. It is a constant process
with the same water going through the cycle over and over
again.
The diagram below shows the different parts
of the water cycle.
The Earth's water
Nearly all (about 97%) of the Earth's water
is contained in the oceans. A tiny amount is locked away
as ice sheets and glaciers. This leaves a very small amount
which travels around in our water cycle, although it may
not always seem this way on wet days.
Stages of the water cycle
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Stage 1
The first stage of the water cycle is
when moisture from the sea and plants is lifted into the
atmosphere.
As the sun beats down it warms the oceans, rivers and
lakes. This causes the water to rise into the air as water
vapour. This process is known as evaporation.
A tiny amount of moisture is also released from trees
and plants. This is known as transpiration.
Stage 2
As the water vapour rises in the atmosphere,
it cools and condenses, forming clouds. This process is
known as condensation.
It is the same process that makes you see your breath
on a cold winter morning. The clouds will then produce
rain or snow (known as precipitation)
which returns to the Earth's surface as water. The cycle
then starts all over again.
Stage 3
Only about three quarters of the rain
which falls back to Earth lands in the oceans. This is
much less than leaves in the first place. The remaining
water makes only a slow return to the oceans. Most is
locked up in glaciers and icebergs and can take several
thousands of years to complete its cycle. In tropical
areas the process can take just a few hours.
The remaining water runs slowly overground,
seeps into the ground or is taken up by plants as
the cycle begins again.
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Importance of water
The water cycle is vital for making sure rain
falls around the world. People depend on it for drinking water
for themselves and their animals and also for growing their
food. Droughts
caused by a lack of rain affect many parts of the world causing
famine and many deaths.
Activities
Why not try making your own mini water cycle.
Check out our Water
Cycle in a Bag experiment.
See evaporation working in your school playground
or garden. Check
out our Measuring a Puddle experiment.
If any of these words are new to
you, check out our dictionary of weather
words.
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