Essential to life on Earth, this continuous process moves water throughout the Earth and its atmosphere.
The water cycle has 4 key processes which help to move water and transform it into different forms:
- Evaporation: the process of water transforming into a gaseous substance (water vapour or steam) due to an increase in temperature (via heat or light).
- Condensation: the process of a gaseous substance transforming into a liquid state
- Transpiration: the process of water passing through a plant and its evaporation thorough the leaves, stems and flowers.
- Precipitation: when water falls to the Earth's surface in the form of rain, heat, sleet, snow or mist.
Sunlight from the sun causes water (in the form of the sea, rivers, wetlands, dew) to evaporate and rise into the air as water vapour. This vapour then forms clouds in our atmosphere. As the temperature cools, water vapour falls back to Earth in the form of rain, hail, snow or mist in a process called precipitation. Some of this precipitation will evaporate and return to the atmosphere or soak into the ground. This ground water can then feed plants and grass through transpiration, or flow into our rivers, streams, lakes, wetlands or ocean.
The amount of water we have on Earth never changes and the water cycle is a natural way of recycling and transporting water throughout the planet.
Did you know?
- Water expands by 9% when it freezes.
- 97% of the Earth's water is in the oceans and seas.
- 70% of the world’s surface is water.
- Water dissolves more substances than any other liquid.
- A litre of water at 4°C weighs 1.0kg.
- Water is the only substance on Earth that can be found in 3 different forms – solid, liquid or gas.
Test your knowledge with our Water Cycle e-learning game!
The Water Cycle