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WATER:
ü The water is very important for all forms of
life.
ü The chemical symbol of water is H2O.
ü Water is a chemical substance.
ü H2O contains two Hydrogen and one oxygen
atoms.
ü Water is liquid.
ü The solid state of water is Ice.
ü The gaseous state of water is stream.
ü The water is mainly available in 3 forms.
v Ground water
v Surface water
v Ice cap and Vapor.
ü The water moves from one pool to the other
and is called Hydrological cycle or water cycle.
ü (Note: We all know that through rain we get
water on to the earth, oceans etc. The same water evaporates and reaches the
atmosphere again precipitates and rains on the earth. This is Hydrological
cycle).
ü Evaporation: This is the transition of water
from liquid state to gaseous state.
ü Transpiration: This is the diffusion of water
into the atmosphere.
ü Through evaporation and transpiration water
is added to the atmosphere.
ü The amount of water that is added to the
atmosphere through evaporation and transpiration and the amount of water that
is returned to the earth in the form of precipitation (rain) is equal. This is
how the global water balance is maintained.
ü (Note:
the important forms of precipitation are rain, snow, hail, sleet etc).
ü Oceans are the largest reservoirs of the
water.
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| OCEAN |
ü Out of the total water that is available on
the earth more than 97 percent is present in the oceans.
ü Ice caps and glaciers account for 2.15
percent of water.
ü The ice caps are the largest
reservoirs of fresh
water.
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| ICE CAPS |
ü The atmosphere contains only 0.001 percent of
water.
ü The amount of the ground water is only 0.635
percent.
ü The total mass of water put together is
called Hydrosphere. (Water covers 71 percent of the earth surface. Out of this the oceans
constitute the majority of the water, Regarding Oceans we discuss later).
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v THE MOST
IMPORTANT SOURCE OF FRESH WATER ON THE EARTH IS PRECIPITATION.
v
THE MOST COMMON SOURCE OF GROUND WATER IS SPRING.
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Does all the
water precipitating from the atmosphere reach the earth?
v
The answer is “No”.
v
Some amount is evaporated in the atmosphere.
v
Some part will be in the form of snowfall.
v
A part is absorbed by the soil in the form of soil water.
v
The remaining water flows over the surface and reaches the sea or ocean
and is called runoff water.
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v
Did you hear Water harvesting? Why is it done?
v
Did you hear some places become dry and the people
suffer with lack of drinking water? Do you know why?
v
In some area there is no harvesting of crops because of
lack of water. Where is the water?
v
Please think about this, we answer at a later stage.
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Now let us try to know some important terms.
v
Percolation: This is a process of water entering the rocks. This happens after the
soil is saturated. Percolation depends on porosity and permeability.
v
Porosity: This is the presence of pores in the rocks.
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| POROSITY |
v
Permeability: The capacity of the rock to allow water to move from upper parts to
the lower parts.
v
Ground water: The water that is percolated and available in the rocks is called the
ground water.
v
Connate water: This is the water that is present in the rocks since its formation.
v
Zone of saturation: The area of the rocks where the pore spaces are completely filled by
water.
v
Water Table: It is the uppermost surface of the Zone of saturation.
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| WATER TABLE |
v
Aquifers: The rocks of the earth that contain water. (These rocks are porous).
v
Aquicludes: The rocks that do not contain any water. (These rocks are non porous).
v
Seepage: This is a limited flow of water on to the ground from a spring.
v
Geyser: This is a periodic jet of hot water and steam. (Old Faithful is a
geyser. This is present in Yellowstone National park in USA. This ejects every
65 minutes).
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| GEYSER |
v
Artesian well: The water comes to the surface on its own without any pressure.
Are the porosity and the permeability permanent? No, over a period
of this is decreased?
·
As more water percolates the pore spaces will be clogged.
·
The mineral particles will expand because of the absorption of the
water and the porosity is reduced.
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ü
The water that is present in the ground is not perfectly horizontal.
ü
There are slopes.
ü
When a water table intersects the ground a spring is formed.
ü
If the hot water emerges out of a spring then it is called hot spring.
ü
If the spring contains minerals then it is called mineral spring.
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