The Amazing Journey of Earth's Water

Did you know that the water you drink today might be the same water a dinosaur drank millions of years ago? This is because Earth’s water is always moving in a big circle called the water cycle. Even though water changes from a liquid to a gas or a solid, the total amount of water on our planet stays about the same.

The sun is the engine that keeps the water cycle moving. Its heat warms up the water in our oceans, lakes, and rivers. When water gets warm enough, it turns into an invisible gas called water vapor. This part of the journey is called evaporation. Plants help too! They pull water from the ground and let it out through tiny holes in their leaves. This is called transpiration.

As the water vapor rises high into the sky, the air gets colder. When the vapor cools down, it turns back into tiny liquid water droplets. These droplets grab onto bits of dust in the air to form clouds. This process is called condensation. You can see condensation on a cold glass of lemonade on a hot day!

When too many water droplets gather in a cloud, they get heavy. Gravity pulls them down to Earth. This is precipitation. Depending on how cold the air is, water can fall as rain, snow, or even ice called hail.

Once the water hits the ground, it has work to do. Some of it flows over the land into streams and oceans. This is called runoff. Other water soaks deep into the soil. It fills up underground spaces called aquifers. This groundwater stays hidden until we pump it up or it flows into a spring.

The water cycle is very important for our weather. It helps move heat around the planet to keep us comfortable. However, when the Earth gets too warm, the water cycle speeds up. This can cause bigger storms or long times without any rain. By understanding the water cycle, we can learn how to protect our planet's most precious resource.