The water cycle

In short: Water evaporates from oceans, lakes and plants, forms clouds, falls to Earth as precipitation and flows back to the sea. This cycle runs constantly and is driven by the Sun.

In more detail: Water on Earth changes between the states solid, liquid and gas (aggregatzustaende).

In detail

• Evaporation and transpiration: The Sun warms water surfaces. Plants also release water vapour through their leaves.
• Condensation: Rising moist air cools, vapour forms droplets and clouds.
• Precipitation: Rain, snow, hail. It feeds rivers, lakes and groundwater.
• Groundwater: Water that seeps in collects in the ground and is an important source of drinking water.
• Amounts: Most water (about 97 percent) is salty. Only a small part is usable fresh water.