Earth: The Earth: The Water PlanetWater Planet

The Water CycleThe Water Cycle

Water Cycle NotesWater Cycle Notes

•The total The total amount of amount of water on the water on the Earth Earth remains remains fairly fairly constant.constant.

•The water The water moves above, moves above, across, and across, and through through Earth’s crust Earth’s crust and and ecosystemsecosystems..

The SunThe Sun

•HeatHeat energy from the sun energy from the sun drives the drives the water cyclewater cycle..

•Heat reaches the Earth by Heat reaches the Earth by radiationradiation..

EvaporationEvaporation

•The process of The process of liquidliquid waterwater changing into changing into waterwater vaporvapor..

•OceansOceans contribute about contribute about 8080% of all the water vapor % of all the water vapor in the air.in the air.

CondensationCondensation

• The process in which The process in which waterwater vaporvapor changes into changes into liquidliquid waterwater as the as the water vapor rises into the air and water vapor rises into the air and coolscools..

• When water vapor condenses on When water vapor condenses on particlesparticles inin thethe airair and tiny water and tiny water droplets or ice crystals form, a droplets or ice crystals form, a cloudcloud is visible.is visible.

PrecipitationPrecipitation

• SolidSolid or or liquidliquid water that falls from the air water that falls from the air to Earthto Earth

• RainRain, , snowsnow, , sleetsleet, and , and hailhail are forms of are forms of precipitation.precipitation.

• Form when drops of Form when drops of condensationcondensation in in clouds come together and grow clouds come together and grow tootoo largelarge to remain to remain suspendedsuspended

• Precipitation always “runs” Precipitation always “runs” downwarddownward due due to to gravitygravity

All precipitation starts as All precipitation starts as snowsnow!!

• Snow falls into warm air and meltsSnow falls into warm air and melts = = rainrain

• Snow falls into cold air and never melts Snow falls into cold air and never melts on the way downon the way down==snowsnow

• Snow falls, melts, and refreezes as it Snow falls, melts, and refreezes as it travels through cold airtravels through cold air==sleetsleet

• Snow falls, melts, refreezes and becomes Snow falls, melts, refreezes and becomes the “seed” kept suspended by updrafts the “seed” kept suspended by updrafts until it gets too heavy and fallsuntil it gets too heavy and falls==hailhail

““Lake Effect” SnowLake Effect” Snow

•Cold , dry air blows over Cold , dry air blows over large lakes and then large lakes and then over landover land

Where does precipitation Where does precipitation go?go?

• Most Most falls back into the oceanfalls back into the ocean

• Some falls on the ground and Some falls on the ground and soakssoaks inin

• Some falls on the ground and Some falls on the ground and runsruns offoff the surface into the surface into tributariestributaries (streams (streams and small rivers that feed into a main and small rivers that feed into a main river)river)

TranspirationTranspiration

• The process by which The process by which plants release plants release water vapor into the air through their water vapor into the air through their leavesleaves

GroundwaterGroundwater

• Water located in the Water located in the gapsgaps and and porespores in rocks below in rocks below earth’searth’s surfacesurface..

• Water gets there because the soil in Water gets there because the soil in places is places is permeablepermeable which means which means water can easily pass throughwater can easily pass through..

• It can collect in large underground It can collect in large underground lakes called lakes called aquifersaquifers..

• WellsWells can be dug to access can be dug to access groundwater.groundwater.

Fresh WaterFresh Water

• Humans are Humans are 60%60%--75%75% water. water.

• Plants Plants useuse water to water to make their own foodmake their own food..

• Both humans (animals) and plants need Both humans (animals) and plants need fresh waterfresh water..

• Fresh water has a very low Fresh water has a very low saltsalt contentcontent

• Only about Only about 3%3% of all the water on Earth of all the water on Earth is fresh water.is fresh water.

• Of that 3% over 2% is Of that 3% over 2% is frozenfrozen..

Preserving Water ResourcesPreserving Water Resources

• Since Since groundwatergroundwater is our richest source of is our richest source of fresh water, we must be careful with fresh water, we must be careful with disposing of chemicalsdisposing of chemicals..

• WaterWater treatmenttreatment factories can filter and factories can filter and partially purify water. (Boise WaterShed)partially purify water. (Boise WaterShed)

• WetlandsWetlands act as act as natural water natural water filtersfilters as some waste settles out, is absorbed by as some waste settles out, is absorbed by plants, and silt and mud are trapped by plants, and silt and mud are trapped by plantplant rootsroots..