The The Water CycleWater Cycle

Water is…Water is…

The only common The only common substance that substance that exists exists as a solid, a liquid, and as a solid, a liquid, and a gas.a gas.

Present everywherePresent everywhere on on Earth.Earth.

In a In a continuous state continuous state of changeof change and and movement.movement.

The Water CycleThe Water Cycle

Definition:Definition: the combination the combination of all of theof all of the different movements of waterdifferent movements of water

Also known as the Also known as the hydrologic cyclehydrologic cycle A A flow of matter (water) and energyflow of matter (water) and energy Called a Called a “closed” system“closed” system

– A material [water] moves from place to place A material [water] moves from place to place but but nothing is gained nor lost.nothing is gained nor lost.

The Water CycleThe Water Cycle

Major Processes of the Water CycleMajor Processes of the Water Cycle

EvaporationEvaporation and and PrecipitationPrecipitation

There is There is more evaporationmore evaporation than precipitation over the than precipitation over the surface of the surface of the Earth’s Earth’s oceans.oceans.

There is There is more precipitationmore precipitation than evaporation over the than evaporation over the surface of the surface of the Earth’s Earth’s continents.continents.

EvaporationEvaporation

Definition: the change Definition: the change of state of matter from of state of matter from a a liquid to a gas.liquid to a gas.

Heat is absorbed.Heat is absorbed. Example: boiling water Example: boiling water

to steamto steam

OceansOceans

CoverCover about about 75% of the Earth75% of the Earth Ocean water is Ocean water is constantly evaporatingconstantly evaporating into into

the atmosphere (becomes water vapor)the atmosphere (becomes water vapor) When When water vapor coolswater vapor cools::

– Forms Forms clouds at higher altitudesclouds at higher altitudes– Forms Forms fog if close to the groundfog if close to the ground

PrecipitationPrecipitation

Definition: Definition: water that falls to the surfacewater that falls to the surface from the from the atmosphere as rain, snow, hail, or sleetatmosphere as rain, snow, hail, or sleet

After the precipitationAfter the precipitation

Water can take Water can take different routes:different routes:– Evaporate Evaporate – Ground WaterGround Water– Soil MoistureSoil Moisture– Surface runoffSurface runoff

EvaporationEvaporation

Back into the atmosphereBack into the atmosphere The higher the temperature, the faster The higher the temperature, the faster

evaporation occurs.evaporation occurs.

Ground WaterGround Water

Water soaks into the ground until it reaches Water soaks into the ground until it reaches a zone where all of the pores are filled with a zone where all of the pores are filled with water.water.

Example: underground streams, aquifersExample: underground streams, aquifers

Soil MoistureSoil Moisture

Water that remains in Water that remains in the surface layer of soilthe surface layer of soil

the roots of plants the roots of plants absorb this water.absorb this water.– Travels up through the Travels up through the

stems and branches of stems and branches of the plant into the leaves the plant into the leaves and is and is released into the released into the atmosphere as vaporatmosphere as vapor in in a process called a process called transpirationtranspiration..

Surface RunoffSurface Runoff

Water that flows Water that flows downhill into streams downhill into streams and riversand rivers

Eventually empties into Eventually empties into the oceanthe ocean

What makes the ocean salty?What makes the ocean salty?

Water flows from the surface of the Water flows from the surface of the continents into the oceanscontinents into the oceans

This water carries sediment particles and This water carries sediment particles and dissolved minerals into the ocean.dissolved minerals into the ocean.

When ocean water evaporates, it leaves the When ocean water evaporates, it leaves the sediments behind.sediments behind.

Over time, the ocean becomes more and Over time, the ocean becomes more and more salty.more salty.

Reservoir vs. FluxReservoir vs. Flux

Reservoir – a place in the Earth system that Reservoir – a place in the Earth system that holds waterholds water..– Ex. Ex. Oceans, Atmosphere, CloudsOceans, Atmosphere, Clouds, etc, etc

Flux – the Flux – the movement of watermovement of water from one from one reservoir to another.reservoir to another.

Energy is requiredEnergy is required to make water flow from to make water flow from one reservoir to another.one reservoir to another.

On average, the total amount of water in all On average, the total amount of water in all reservoirs combined is nearly the same. reservoirs combined is nearly the same.

The amount of water stored in any one The amount of water stored in any one reservoir varies over time.reservoir varies over time.