Water cycle

The surface of the earth is for a large part covered in water: about 70%. Of all the water on earth only about 3% is fresh water. Most of that fresh water is ice in pole caps and glaciers. Only 0,014% of all water can be used by people.

The sun warms the water in the oceans and seas and turns the water into water vapour (evaporation). High up in the atmosphere the air cools down and this vapour turns into tiny water droplets (condensation) which together form clouds. Part of these clouds rain out over sea. This is called the short water cycle.

In the long water cycle the droplets will go on a longer journey. The clouds float on air currents. Droplets fall down as snowflakes, or icicles, or raindrops (precipitation). They may fall on land or in a river or a lake. Water that falls on land may stay there as snow or ice or it may seep into the earth and become soil moisture or ground water (infiltration). Soil water is bound to the soil and is available for plants. Ground water can fill the empty spaces in the ground and can form underground rivers or lakes. Water may also flow over land and eventually enter a river. In the end it can flow all the way back to sea (transportation) or evaporate again somewhere along the way.

This animation shows the long watercycle, somewhat simplified. Watch the evaporation, condensation, precipitation, infiltration and transportation of water! Do you now know what these words mean? Then try the hydrology quiz!