19998051 Hydrological Cycle

7/28/2019 19998051 Hydrological Cycle

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Hydrological Cycle


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The Hydrologic Cycle

(Water Cycle)

The path water takes as it circulates from

the land to the sky and back again. Water

is recycled this way so we do not run out.So every time you get a drink of water

remember you are drinking the same

water the dinosaurs drank.


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Parts of the hydrologic cycle

Evaporation

Condensation

Precipitation


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Evaporation

Evaporation is when

the sun heats up

water in rivers or

lakes or the oceanand turns it into

vapor or steam. The

water vapor or

steam leaves theriver, lake or ocean

and goes into the

air.


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Evapotranspiration

Evaporation often implicityincludes transpiration fromplants, though togather theyare specifically refered to asEvapotranspiration. Herewater given off through thepores of plants and animals

joins the atmosphere as avapor.

Annual Evapotranspirationamounts approximately =505,000 km of water

From the ocean = 434,000

km.


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Condensation

Water vapor inthe air gets coldand changesback into liquid,formingclouds. This is

calledcondensation.


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Precipitation

Precipitation occurs whenso much water has

accumulated that the aircannot hold itanymore. The clouds get

heavy and water falls backto the earth in the form ofrain, hail, sleet or snow.


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Run-off When the precipitation

reaches the ground, severalthings can happen to it. First,it might be re-evaporated.For instance, we have all

seen the mist rising off hotroads after a summershower.

If it isnt re-evaporated,

much of the water willbecome RUNOFF that goesinto streams, lakes andrivers as it flows back to the

ocean.


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Infiltration

Some of the precipitation willbe absorbed into the ground.

This is called INFILTRATION.

Once in the ground, the water

can join the earths groundwater supply.

This is one of the worlds

largest store house of water.

The water could also be

absorbed from the ground by

the roots of plants.


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Reservoirs

The largest reservoir is the collection of

oceans, accounting for 97% of the Earths

water. The next largest quantity(2%) is stored

in solid form in ice caps and glaciers.

The small amount accounts for

approximately(75%) of all fresh water reserves

on the planet. The water contained within allliving organisms represents the smallest

reservoir


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Volume of water stored in the water

cycle reservoirs

Reservoir Volume of water(106km

Percent of total%

Oceans 1370 97.25%

Icecaps,glaciers 29 2.05%Ground water 9.5 0.68%

Lakes 0.125 0.01%

Soil moisture 0.625 0.005%Atmosphere 0.013 0.001%

Streams&rivers 0.0017 0.0001%

Biosphere 0.0006 0.00004%


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Residence times

The residence time of a reservoir within the

Hydrological cycle is the average time awater molecule will spend in that reservoir.

It is a measure of the average age of thewater in that reservoir, though some water

will spend much less time than average, and

some much more.


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Average reservoir residence times

Reservoir Avg residence time

Oceans 3,200 years

Glaciers 20100 years

Seasonal snow cover 2-6 months

Soil moisture 1-2 months

Ground water-shallow 100-200 years

Ground water-deep 10,000 years

Lakes 50-100 years

Rivers 2-6 months

Atmosphere 9 days


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Effects on climate

The water cycle is powered from solarenergy.

86% of the global evaporation occurs from

the oceans, reducing their temperature byevaporative cooling.

Without the cooling effect of evaporation the

green house effect would lead to a muchhigher surface temperature of 67c, and a

warmer planet


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Effects on Biogeochemical cycling

While the water cycle itself a biogeochemicalcycle, flow of water over and beneath the

Earth is a key component of the cycling of

other biogeochemical Runoff is responsible

for almost all of the transport of eroded

sediment and phosphorus from land to water

bodies.

The salinity of oceans is derived fromerosion and transport of dissolved salts from

the land.


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Agriculture

Industry waste

Alteration of the chemical composition of the

atmosphere

Construction of dams

Deforestation and Afforestation

Removal of ground water from wells

Dont alter the

water cycle


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Cont

Water abstraction from rivers

Urbanization

Contributing to climate change

Withdrawing large amount of fresh water

Clearing Vegetation and underground water

Polluting surface and underground water

Precipitation changes worldwideGlaciers melt-loss of water source

Over population

Wild fires accelerate several cycles


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Discussions


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19998051 Hydrological Cycle

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