Top 11 Water Cycle (Part 2)

7/30/2019 Top 11 Water Cycle (Part 2)

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CHEM115 Environmental Chemistry

Background Source: www.opus1.com 1

CHAPTER 11

(part 2)

HYDROLOGIC CYCLE





Water Cycle

Only about 0.001% of the total water on earth is

in the atmosphere anytime.

Around 85% of all water that enters the

atmosphere is derived from the ocean.

More than 99% of earth’s water in its natural state

is unavailable for beneficial human use.





Where is water found?

Location % of water Avg. Residence time

Oceans 97.20 thousands of year

Ice caps and glaciers 2.15thousands of years andlonger

Atmosphere 0.0010 9 day

Fresh water lakes 0.0009 tens of years

Groundwater (to depthof 0.8km) 0.31

hundreds to thousands of years

Rivers and streams 0.0001 2 weeks





Hydrologic Cycle

Cloud formation

Rain clouds

Precipitation

Infiltration

Percolation

Groundwater Rock

Soil

Ocean

To ocean

Surface runoff



Hydrological Cycle







Source: http://oceanworld.tamu.edu/resources/oceanography-book/Images/water-cycle.jpg



Hydrological Cycle

Circurlation and conservation of earth’s water as itcirculates from the land to the sky and back again is

called the ‘hydrological cycle’ or ‘water cycle’.

The stages of the cycle are:

• Evaporation

• Transport

• Condensation

• Precipitation

• Groundwater

• Run-off CHEM115 Environmental Chemistry




Hydrological CycleEvaporation

• Process by which water changes from a liquid to a gas.

The sun’s heat provides energy to evaporate water from

the earth’s surface. Land, lakes, rivers and oceans send

up a steady stream of water vapour and plants also lose water to the air (transpiration).

• Approximately 80% - oceans

20% - inland water and vegetation.





Transport• The movement of water through the

atmosphere, specifically from over the oceans to

over land.• Some of the earth’s moisture transport is visible as

clouds, which themselves consist of ice crystals and/or

tiny water droplets.

• Most water is transported in the form of water vapour, which is actually the third most abundant gas in the

atmosphere. CHEM115 Environmental Chemistry


Hydrological Cycle



Condensation• The transported water vapour

eventually condenses , forming tiny droplets in

clouds.

Precipitation

• Primary mechanism for transporting water fromthe atmosphere to the surface of the earth.



Hydrological Cycle



Hydrological CycleGroundwater

• Some of the precipitation soaks into the ground and

this is the main source of the formation of the waters

found on land - rivers, lakes, groundwater and glaciers.

• Some of the underground water is trapped betweenrock or clay layers.

• Under special circumstances, groundwater can even

flow upward in artesian wells. The flow of groundwater

is much slower than run-off with speeds usually

measured in centimetres per day, metres per year or

even centimetres per year.CHEM115 Environmental Chemistry




Hydrological CycleRun-off

• Most of the water which returns to land flows

downhill.

• Different surfaces hold different amounts of

water and absorb water at different rates. As a

surface becomes less permeable, an increasing

amount of water remains on the surface,

creating a greater potential for flooding .







Evaporation and transpiration are important inhydrologic cycle.

Evaporation of water reduces the temperature.Condensation is exothermic and increase temp

at the air/water interface.





Water infiltrating the ground will either reach water table or be taken up by plants.

Though water is trapped as glaciers or ice caps in

cold regions for thousand years, eventually it

returns to hydrologic cycle when ice caps andglaciers melt.



Bonus (0.5)

Briefly describe the evaporation process inhydrological cycle.



Top 11 Water Cycle (Part 2)

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