The water cycle

Have you ever wondered where rain comes from, or where the water goes when a puddle dries up? The answer is a journey that never stops and has repeated for millions of years: the water cycle. It works like a giant wheel that moves water all around the planet, and thanks to it we have rivers, clouds, plants and, of course, ourselves.

1. The Sun heats the water

Everything starts with the Sun. Its rays warm the seas, lakes and rivers, and some of the water turns into vapor, a gas so tiny that we cannot see it. This step is called evaporation. Water also evaporates from wet laundry, from puddles and from the leaves of plants.

2. The vapor rises and forms clouds

Vapor is light, so it rises through the air. The higher it goes, the colder it gets, and the vapor cools down and turns back into tiny droplets of water. This is condensation. Millions of droplets together make a cloud. If you have ever seen a bathroom mirror or a cold glass of water fog up, you have seen condensation on a small scale.

3. Clouds release the water

When the droplets in a cloud join together and become too heavy, they fall. If it is warm, rain falls; if it is very cold, the water freezes and falls as snow or hail. We call this precipitation.

4. The water starts again

Rainwater soaks the ground, feeds the plants, fills the rivers, and the rivers carry it back to the sea. Some of it seeps underground and becomes groundwater, and mountain snow, when it melts in spring, also flows down to the rivers. Then the Sun warms it again and the cycle starts over.

Experiment: make your own water cycle!

You need a zip-top plastic bag, a permanent marker and a little water. Draw a sun and a cloud on the bag, pour a little water into the bottom, seal it well and tape it to a sunny window. After a few hours you will see droplets on the inside of the bag: the water has evaporated, condensed and is falling again. You have made a tiny water cycle!

Why it matters so much

The water on Earth is always the same: it is never created or lost, it just changes place and form. That is why it is so important to look after it and not waste it. Every drop you drink has passed through clouds, rivers and seas many times. Understanding the water cycle helps us value something as simple as turning on the tap.

💡 The water you drink was already around in dinosaur times.