water cycle(present)

7/31/2019 Water Cycle(Present)

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What is this? The water cycle, also known as the hydrologic

cycle or H2O cycle, describes the continuousmovement of water on, above and below the surface ofthe Earth.

The water moves from one reservoir to another, suchas from river to ocean, or from the ocean to the

atmosphere, by various physical processes. The water goes through different phases: liquid, solid,

and gas.


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How it happens?


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The sun heats the water bodies and the surroundings.

Water evaporates from heated water bodies and soil,and also is transpired by plants.

Rising hot air takes the vapors into cooler altitudes ofthe atmosphere where it condenses to form clouds.

Cloud particles collide, grow, and fall out of the skyas precipitation.

Precipitation takes place in the form of Rain

fall(mainly), Hail or Snow, and Sleet. Most of the water comes back to the Oceans and Seas.

Part forms Ice caps and Glaciers, and part remains asGround water and other fresh water sources.


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Different processes involved in water cycle:

Evaporation Precipitation: It is any product of condensation of water vapour that falls to

the earth under gravity.

Canopy Interception: The precipitation that is intercepted by the plantfoliage, eventually evaporates back to the atmosphere rather than falling to theground.

Snowmelt

Runoff: It is the variety of ways by which water moves across the land.

Infiltration: It is the flow of water from the ground surface into the ground.

Subsurface Flow: It is the flow of water underground (through wetunderground layer of permeable rocks or consolidated materials)

Advection: It is the movement of water- in solid, liquid, or vapor states,through the atmosphere. Without advection, water that evaporated over theoceans may not precipitate over land.

Condensation

Transpiration: It is the release of water vapor from plants and soil into the air.


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Effects of Water Cycle Effects on Climate: The water cycle is powered from solar energy. 86% of

the global evaporation occurs from the oceans, reducing their temperaturebyevaporative cooling. Without the cooling, the effect of evaporation onthe greenhouse effect would lead to a much higher surface temperatureof 67 C (153 F), and a warmer planet.

Effects on Biogeochemical Cycling: Flow of water over and beneath theEarth is a key component of the cycling of other biogeochemicals. Runoffis responsible for almost all of the transportof eroded sediment and phosphorous from land to water bodies.The salinity of the oceans is derived from erosion and transport ofdissolved salts from the land.


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Humans affects the Water Cycle agriculture

industry

alteration of the chemical composition of theatmosphere

construction of dams

deforestation and afforestation

removal of groundwater from wells

water abstraction from rivers

urbanization


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Facts of Water Cycle

[It is estimated that of the (1,386,000,000 km3) of the world's watersupply, about (1,338,000,000 km3) is stored in oceans, or about 95%. Itis also estimated that the oceans supply about 90% of the evaporated

water that goes into the water cycle. ]

During colder climatic periods more ice caps and glaciers form, andenough of the global water supply accumulates as ice to lessen theamounts in other parts of the water cycle. The reverse is true during

warm periods. [About three million years ago the oceans could havebeen up to 165 ft (50 m) higher.]

Glacial retreat is also an example of a changing water cycle, where thesupply of water to glaciers from precipitation cannot keep up with theloss of water from melting and sublimation. Glacial retreat since1850 has been extensive.


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water cycle(present)

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