Curriculum fit: KS3 Geography and Science (water cycle); GCSE Geography (hydrology, depending on board). US: middle school Earth science (Earth's systems).
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What Is It?
The water cycle describes how water moves between the oceans, the atmosphere and the land. It is driven mainly by energy from the Sun, and gravity moves water downhill.
Water is never used up. It changes state and moves around the planet in a continuous cycle.
Key Formulas and Ideas
- Evaporation: liquid water becomes water vapour, powered by the Sun.
- Transpiration: plants release water vapour from their leaves.
- Condensation: vapour cools and forms clouds. Precipitation: rain, snow, sleet or hail.
- Surface runoff, infiltration and groundwater flow return water to rivers, lakes and the sea.
Worked Examples
Follow a Water Molecule
Describe the journey of water from the sea back to the sea.
- Sun's heat evaporates water from the sea.
- The vapour rises, cools and condenses into clouds.
- It falls as rain over land, runs into rivers and returns to the sea.
✓ Answer Evaporation, condensation, precipitation, then runoff
Human Impact
How could cutting down a large forest affect the water cycle?
- Fewer trees mean less transpiration.
- Less water vapour enters the air, and runoff may increase.
✓ Answer Less transpiration and more surface runoff
A Simple Model
How can you model the water cycle at school?
- Put a little water in a clear sealed bag and place it in a warm, sunny spot.
- Water evaporates and condenses on the bag, then runs down like rain.
✓ Answer A sealed bag shows evaporation, condensation and runoff
Common Mistakes to Avoid
- Saying water is created or destroyed in the cycle.
- Confusing evaporation and condensation.
- Forgetting transpiration from plants.
- Describing the cycle as if it only involves rain.
Practice Questions
Frequently Asked Questions
Is the water cycle powered by anything?
Yes. Mostly energy from the Sun, with gravity moving water downhill.
What drives the water cycle?
Mainly energy from the Sun, with gravity moving water downhill.
Keep Going With These Guides
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KS3GCSEMiddle SchoolHigh SchoolClimate Change: The Greenhouse Effect and the 1.5°C Target
Understand the greenhouse effect, what the Paris Agreement's 1.5°C goal means and the difference between mitigation and adaptation.
GCSEA-LevelHigh SchoolAPPlate Tectonics: Boundaries, Earthquakes and Volcanoes
Learn how Earth's plates move, the three types of plate boundary and why earthquakes and volcanoes happen, with real examples.
KS3GCSEMiddle SchoolHigh SchoolSources and Review
- DfE: National curriculum in England, geography programmes of study (key stages 1 to 3)
- Next Generation Science Standards: search the standards
Reviewed by StudyMorrow editorial review on 5 Nov 2026.