THE WATER CYCLETHE WATER CYCLE

© Copyright 2007.  M. J. Krech.

The Water CycleThe Water Cycle

WWater is constantly ater is constantly being cycled between being cycled between the atmosphere, the the atmosphere, the ocean and land. This ocean and land. This cycling is a very cycling is a very important process that important process that helps sustain life on helps sustain life on Earth. Earth. 

Each part of the cycle drives the other parts.

EvaporationEvaporation

Evaporation is Evaporation is the process the process where a liquid, where a liquid, in this case in this case water, changes water, changes from its liquid from its liquid state to a state to a gaseous state.gaseous state.

EvaporationEvaporation Some of the Some of the

water in the water in the oceans and oceans and freshwater freshwater bodies, such bodies, such as lakes and as lakes and rivers, is rivers, is warmed by warmed by

the sun and the sun and evaporates.evaporates.

EvaporationEvaporation During the process During the process

of evaporation, of evaporation, impurities in the impurities in the water are left water are left behind. As a result, behind. As a result, the water that goes the water that goes into the into the atmosphere is atmosphere is cleaner than it was cleaner than it was on Earth. on Earth. 

CondensationCondensation Condensation Condensation

is the is the opposite of opposite of evaporation. evaporation. Condensation Condensation occurs when a occurs when a gas is gas is changed into changed into a liquid.a liquid.

CondensationCondensation

When the water When the water droplets formed droplets formed from from condensation condensation are very small, are very small, they remain they remain suspended in the suspended in the atmosphere. atmosphere.

CondensationCondensation These These

millions of millions of droplets of droplets of suspended suspended water form water form clouds in clouds in the sky or the sky or fog at fog at ground ground level.level.

PrecipitationPrecipitation When the When the

temperature and temperature and atmospheric atmospheric pressure are right, pressure are right, the small droplets the small droplets of water in clouds of water in clouds form larger form larger droplets and droplets and precipitation precipitation occurs. The occurs. The raindrops fall to raindrops fall to Earth.  Earth. 

Surface RunoffSurface Runoff Much of the Much of the

water that water that returns to Earth returns to Earth as precipitation as precipitation runs off the runs off the surface of the surface of the land, and flows land, and flows downhill into downhill into streams, rivers, streams, rivers, ponds and lakes.ponds and lakes.

Surface RunoffSurface Runoff Small Small

streams flow streams flow into larger into larger streams, streams, then into then into rivers, and rivers, and eventually eventually the water the water flows into flows into the ocean.  the ocean. 

Surface RunoffSurface Runoff Surface runoff is Surface runoff is

an important part an important part of the water cycle of the water cycle because, through because, through surface runoff, surface runoff, much of the water much of the water returns again to returns again to the oceans, where the oceans, where a great deal of a great deal of evaporation evaporation occurs. occurs. 

PercolationPercolation Percolation is an Percolation is an

important process important process where rain water where rain water soaks into soaks into (infiltrates) the (infiltrates) the ground, into the ground, into the soil and underlying soil and underlying rock layers. rock layers.

PercolationPercolation

Some of this Some of this water water ultimately ultimately returns to returns to the surface the surface at springs or at springs or in low spots in low spots downhill. downhill.

Percolation Percolation (Infiltration)(Infiltration)

Some of the water Some of the water percolatespercolates underground underground

and is called and is called groundwatergroundwater..   

GroundwaterGroundwater As the water As the water

moves through moves through the soil and the soil and rock layers, rock layers, many of the many of the impurities in impurities in the water are the water are filtered out. filtered out. This filtering This filtering process helps process helps clean the water. clean the water.

GroundwaterGroundwater

Water moves Water moves into caves into caves formed by formed by carbonation, carbonation, forming many forming many other other KarstKarst features.features.

TranspirationTranspiration One final One final

process is process is important in the important in the water cycle. As water cycle. As plants absorb plants absorb water from the water from the soil, the water soil, the water moves from the moves from the roots through roots through the stems to the the stems to the leaves. leaves.

TranspirationTranspiration Once the water Once the water

reaches the reaches the leaves, some of leaves, some of it evaporates it evaporates from the leaves, from the leaves, adding to the adding to the amount of amount of water vapor in water vapor in the air. the air.

TranspirationTranspiration This process of This process of

evaporation evaporation through plant through plant leaves is called leaves is called transpirationtranspiration. In . In large forests, an large forests, an enormous amount enormous amount of water will of water will transpire through transpire through leaves.  leaves. 

EvaporationEvaporation And we’re back And we’re back

to to EvaporationEvaporation again! The again! The endless cycle of endless cycle of water moving water moving through our through our planet goes on planet goes on and on and and on and on…on…

The Water CycleThe Water Cycle Condensation Condensation

transpiration, transpiration, precipitation and all precipitation and all the othersthe others are part are part

of of the water the water cyclecycle, a complex , a complex process that not only process that not only gives us water to gives us water to drink and food to drink and food to eat, but also the eat, but also the weather patterns weather patterns that help grow our that help grow our crops.  crops. 

WATERWATER Water is an Water is an integralintegral part of part of life on this planet.life on this planet.

THE ENDTHE ENDBONUS QUESTIONS:

1. Why is clean water important to you?

2. How does the water cycle contribute to

clean water?