The water cycle — Earth science, 7–10 years
Water moves between the ground, air, rivers, lakes and oceans. It changes form, but the same water can travel around Earth again and again.
Water keeps moving
Sunlight warms water in seas, lakes and puddles, and some of it becomes invisible vapour. Higher up, vapour cools into tiny drops, making clouds. Water then falls as rain or snow and returns through streams, soil and plants.
Why does rain return?
A puddle disappearing can seem like water has vanished. The water cycle solves that puzzle by showing where it goes: into the air, clouds, falling rain, and the ground. This matters because living things need fresh water, while Earth keeps moving the same supply.
From puddle to rain
After a shower, a puddle lies in the playground. First, sunlight warms it and some water evaporates. The vapour rises and cools, joining other droplets in a cloud. When the droplets grow heavy enough, rain falls and can make another puddle.
The common mix-up
A common mistake is saying that clouds are made of water vapour, because vapour rises from warm water. That idea feels sensible, since both are linked to evaporation. Clouds are mostly tiny liquid drops or ice crystals; invisible vapour has cooled and changed form.
Planning water
Farmers, town planners and sailors watch the water cycle for practical reasons. It helps them think about rain, stored water and dry periods. A rain barrel, a reservoir or a field drain works with parts of the cycle, but none creates unlimited fresh water.
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