The Water CycleThe Water Cycle

Water, water everywhere?Water, water everywhere?

The HydrosphereThe Hydrosphere

• Oceans cover approximately 71% of Earth’s surface.

Most of Earth’s water is in the oceans. Less than 3% is freshwater. And less than 1/3 of that can be used as drinking water.

The Water CycleThe Water Cycle

•The process by which Earth’s water moves in and out of the atmosphere.

The Sun’s RoleThe Sun’s Role

•The sun provides the energy that powers the water cycle.

EvaporationEvaporation• The Sun warms Earth’s surface. Water The Sun warms Earth’s surface. Water

molecules heat up and change from a molecules heat up and change from a liquid to a gas (water vapor). The water liquid to a gas (water vapor). The water vapor is circulated by winds and carried vapor is circulated by winds and carried upward by rising, warm air.upward by rising, warm air.

CondensationCondensation• As the air carrying water vapor rises As the air carrying water vapor rises

and cools it changes back to water and cools it changes back to water droplets and forms clouds.droplets and forms clouds.

PrecipitationPrecipitation

• When the water When the water droplets become droplets become large enough they large enough they fall back to the fall back to the surface as surface as precipitation.precipitation.

• This can be rain, This can be rain, sleet, snow or sleet, snow or hail. hail.

Rain

Sleet

Snow

Hail

RunoffRunoff• If the precipitation If the precipitation

falls on land it may falls on land it may become runoff, water become runoff, water that runs downhill that runs downhill into rivers or into rivers or streams.streams.

GroundwaterGroundwater• If precipitation seeps If precipitation seeps

(infiltrates) into the (infiltrates) into the earth it may become earth it may become groundwater, water groundwater, water that has filled pore that has filled pore spaces in the spaces in the ground.ground.

• Porosity and Porosity and saturation effect saturation effect infiltration. If the infiltration. If the surface is non-surface is non-porous saturated or porous saturated or steep it will become steep it will become runoff.runoff.

TranspirationTranspiration

• Groundwater is available Groundwater is available to plants. to plants.

• Plant’s roots take in Plant’s roots take in water that has seeped water that has seeped into the soil. into the soil.

• The water is transported The water is transported to the leaves and to the leaves and released back into the released back into the atmosphere by the atmosphere by the process of transpiration.process of transpiration.

• Groundwater seeps through Groundwater seeps through Earth’s crust and may end up in Earth’s crust and may end up in rivers, lakes or the ocean.rivers, lakes or the ocean.

• When this happens the water When this happens the water cycle starts all over again.cycle starts all over again.