The water cycle

That glass of water you drank yesterday, do you remember it? Can you guess how old that water was?
That water probably fall as rain a couple of days ago not far from your home. But it's older than a couple of days. It's millions years old. Maybe as old as 4.800 million years old.

When the first fish crawled out of the ocean, onto the land, your glass of water was part of that ocean. When the Tyrannosaurus Rex walked the earth it might have drank the same water that you drank. Presidents, kings and queens, Columbus, Napolion and your great great grandfathers all drank that very same water. The water is as old as the earth.

The amount of water is limited and this same water keeps going around and around. We call i the "Water Cycle" This cycle is made out of four main parts:

• Evaporation (and transpiration)
• Condensation
• Precipitation
• Collection

1. Evaporation
Evaporation is when the sun heats up water in the ocean, rivers or lakes and turns the water into vapor or steam. The water vapor or steam leaves the ocean, river or lake and goes into the air. Even plants transpire, transpiration is the process by which plants lose water out of their leaves. Transpiration gives evaporation a bit of a hand in getting the water vapor up into the air.

2. Condensation
Water vapor in the air raises and gets cold and changes back into liquid, forming clouds. This is called condensation. You can see the same sort of thing at home, take a cold water bottle out of the fridge and se what happends, water forms on the outside of the bottle. That water didn't somehow leak through the bottle! It actually came from the air. Water vapor in the warm air, turns back into liquid when it touches the cold glass.

3. Precipitation
Precipitation occurs when so much water has condensed that the clouds cannot hold it anymore. The clouds get heavy and water falls back to the earth in the form of rain, hail or snow.

4. Collection
When water falls back to earth as precipitation, it may fall back in the oceans (71% of the earth surface), lakes or rivers or it may end up on land. When it ends up on land, it will either go into the soil or ground and become part of the “ground water” that plants use or it may run over the ground and collect in the oceans, lakes or rivers where the cycle starts all over again.