Science
What is the water cycle?
Quick answer
The water cycle is the endless movement of water between the land, the sea and the sky. Water evaporates, condenses into clouds, falls as rain or snow and collects in rivers and oceans.
In one sentence
The water cycle is the way water keeps moving round and round between the sea, the sky and the land, powered by the Sun.
Explained
The water on Earth today is the same water that has been here for millions of years. It just keeps moving and changing state. The water in your glass may once have fallen as rain on dinosaurs.
The cycle has four main stages:
- Evaporation. The Sun warms water in oceans, lakes, rivers and puddles. Some of it turns into an invisible gas called water vapour and rises into the air. Plants also give off water vapour from their leaves. See evaporation.
- Condensation. As the vapour rises, it cools. Cool vapour turns back into tiny droplets of liquid water, or ice crystals, which gather together to form clouds.
- Precipitation. When the droplets join and grow too heavy to float, they fall as rain, or as snow, sleet or hail if it is cold enough.
- Collection. The water lands in seas, lakes and rivers, or soaks into the ground. Rivers carry it back to the sea, and the cycle starts again.
Think of it like a giant recycling system with the Sun as the engine and gravity as the force pulling water back down.
Examples
- A puddle in the playground disappears on a sunny afternoon (evaporation).
- Droplets form on the outside of a cold drink (condensation).
- A thunderstorm in the rainy season (precipitation).
- Rainwater running into drains, streams and rivers (collection).
sun
cloud
rain
wave
Common mistakes
- "Clouds are made of water vapour." Vapour is invisible. Clouds are millions of tiny liquid droplets or ice crystals.
- "Water only evaporates when it boils." Water evaporates at any temperature; heat just makes it happen faster.
- "Rain is new water made in the clouds." No new water is made. Rain is water that evaporated earlier, recycled.
Quick quiz
The water cycle
Check what you know with 4 quick questions.
Question 1 of 4
What is it called when water vapour cools and turns into droplets?
Practise it
Try it
Make a mini water cycle: put a little warm water in a clear bowl, cover with cling film and place an ice cube on top. Watch droplets form and "rain" back down. Then see how it shapes our weather.
Water cycle and weather activities
For grown-ups
Related topics
Evaporation
Evaporation is when a liquid slowly turns into a gas from its surface, like a puddle drying in the sun. It happens faster when it is warm, windy or the liquid is spread out.
Weather
Weather is what the air is like at a particular place and time, such as hot or cold, wet or dry, windy or calm, sunny or cloudy. It changes from day to day.
Solids, liquids and gases
Solids, liquids and gases are the three main states of matter. Solids keep their shape, liquids flow and take the shape of their container, and gases spread out to fill any space.
Rivers
A river is a large stream of fresh water that flows downhill from its source, often in hills or mountains, to its mouth at a sea, lake or another river.
Oceans
Oceans are the huge bodies of salt water that cover most of Earth. There are five: the Pacific, Atlantic, Indian, Southern and Arctic.
Seasons
Seasons happen because Earth is tilted. As Earth orbits the Sun over a year, each half of the planet takes turns leaning towards the Sun, getting more direct sunlight and longer days.