The
Water Cycle
Pour
yourself a glass of water -- and guess how old it is?
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!
The earth has a limited amount of water. That
water keeps going around and around 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
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?
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:
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
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.
