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The Water Cycle
The Water Cycle
If it was not for the small temperature range that allows water to exist in the liquid state, life on the planet would not be possible.
Animation
Animation
The Water Cycle
The Water Cycle
Renewing our valuable water supply on Earth.
We have kept roughly the same amount of water on Earth as solid ice, liquid rain and gaseous water vapor throughout time. It continually cycles and moves from the ocean, polar ice caps, rivers, lakes, wetlands, snow, underground aquifers and water vapor in the clouds.
How Does the Water Cycle Work?
The water cycle is driven by the sun, which evaporates the water on Earth to rise as vapor. It then cycles back to earth as rain or snow and starts all over again. Without this vital cycle there would not be life on Earth, as we know it.
To follow the water cycle you can start in the ocean, which stores more than 95% of the Earth’s water.
1) Water, heated by the sun, evaporates up from the ocean and other waterways to form clouds in the sky. Some water evaporates from plants (transpiration) and a small amount evaporates directly from glacial ice (sublimation).
2) The clouds gather all the tiny water droplets together until they are big enough to fall as rain or snow. This is precipitation. Precipitation falls much more in warm tropical places than in deserts. In colder places precipitation falls as snow.
3) When rain falls on land, it soaks into the groundwater and runs into rivers and streams, on their way to the ocean.
Here the cycle starts all over again!
The water in your glass may have fallen from the sky as rain just last week, but the water itself has been around pretty much as long as the earth has!
When the first fish crawled out of the ocean onto the land, your glass of water was part of that ocean. When the Brontosaurus walked through lakes feeding on plants, your glass of water was part of those lakes. When kings and princesses, knights and squires took a drink from their wells, your glass of water was part of those wells.
The earth has a limited amount of water. That water keeps going around and around and around and around and (well, you get the idea) in what we call the "Water Cycle".
This cycle is made up of a few main parts:
- evaporation (and transpiration)
- condensation
- precipitation
- collection
Evaporation:
Evaporation:
Evaporation is when the sun heats up water in rivers or lakes or the ocean and turns it into vapor or steam. The water vapor or steam leaves the river, lake or ocean and goes into the air.
Do plants sweat?
Do plants sweat?
Well, sort of.... People perspire (sweat) and 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 back up into the air.
Condensation:
Condensation:
Water vapor in the air gets cold and changes back into liquid, forming clouds. This is called condensation.
You can see the same sort of thing at home... Pour a glass of cold water on a hot day and watch what happens. Water forms on the outside of the glass. That water didn't somehow leak through the glass! It actually came from the air. Water vapor in the warm air, turns back into liquid when it touches the cold glass.
Precipitation:
Precipitation:
Precipitation occurs when so much water has condensed that the air cannot hold it anymore. The clouds get heavy and water falls back to the earth in the form of rain, hail, sleet or snow.
Collection:
When water falls back to earth as precipitation, it may fall back in the oceans, lakes or rivers or it may end up on land. When it ends up on land, it will either soak into the earth and become part of the “ground water” that plants and animals use to drink or it may run over the soil and collect in the oceans, lakes or rivers where the cycle starts all over again
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