Page 5 - Curriculum Visions Dynamic Book

The water cycle
Why is water so readily available? It is because it constantly circulates between the oceans,
the air, and the land (including the rocks) in a pattern known as the water cycle. We are all
so familiar with it that we tend to take it for granted. But the water cycle only works because water can occur in the three forms, or states: solid, liquid, and gas, at normal temperatures. We will find out more about the importance of states of matter on
pages 21 to 23.
3. Rain
Rainwater is pure water – it is
not salty and normally quite safe
to drink. But it is not easy to catch. When rain falls, most of it immediately sinks into the soil. However, some other living things are better able to use it than us. Most important are plants, which suck up water from the soil through their roots.
6. Floods
4. Rocks
Any rain not used by plants seeps into the ground, first through the soil and then into the rocks below. Water moves very slowly through the rocks. It may take weeks or months to travel to
a river.
5. Rivers and lakes
Once the rocks are full, water begins to seep out at the surface, perhaps as springs, mostly unseen through the beds of rivers and lakes. This (not rainfall) is the main source of water for most rivers.
Finally, rivers carry the water back to sea and so complete the water cycle.
Only during the heaviest rain or after the wettest of seasons do we ever see water flowing on the surface. When it does this, we call the surface water a flood.
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