Introduction:Water is the essential element that makes life
on earth possible. Without water there would be no life. We
usually take water for granted. It flows from our taps when
they are turned on. Most of us are able to bathe when we
want to, swim when we choose and water our gardens. Like
good health we ignore water when we have it.
Although 71% of the earth’s surface is covered by water only
a tiny fraction of this water is available to us as fresh water.
About 97% of the total water available on earth is found in
oceans and is too salty for drinking or irrigation. The
remaining 3% is fresh water. Of this 2.997% is locked in ice
caps or glaciers. Thus only 0.003% of the earth’ total volume
of water is easily available to us as soil moisture,
groundwater, water vapour and water in lakes, streams,
rivers and wetlands.
In short if the world’s water supply were only 100 litres our
usable supply of fresh water would be only about 0.003 litres
(one-half teaspoon). This makes water a very precious
resource. The future wars in our world may well be fought
over water. By the middle of this century, almost twice as
many people will be trying to share the same amount of fresh
water the earth has today. As freshwater becomes more
scarce access to water resources will be a major factor in
determining the economic growth of several countries
around the world.
WATER AVAILABILITY ON PLANET
Water that is found in streams, rivers, lakes, wetlands and
artificial reservoirs is called surface water. Water that
percolates into the ground and fills the pores in soil and rock
is called groundwater. Porous water-saturated layers of sand,
gravel or bedrock through which ground water flows are
called aquifers. Most aquifers are replenished naturally by
rainfall that percolates downward through the soil and rock.
This process is called natural recharge. If the withdrawal rate
of an aquifer exceeds its natural recharge rate, the water
table is lowered. Any pollutant that is discharged onto the
land above is also pulled into the aquifer and pollutes the
groundwater resulting in polluted water in the nearby wells.
India receives most of her rainfall during the months of June
to September due to the seasonal winds and the
temperature differences between the land and the sea.
These winds blow from the opposite directions in the
different seasons. They blow into India from the surrounding
oceans during the summer season and blow out from the
subcontinent to the oceans during the winter. The monsoon
in India is usually reasonably stable but varies geographically.
In some years the commencement of the rains may be
delayed considerably over the entire country or a part of it.
The rains may also terminate earlier than usual. They may be
heavier than usual over one part than over another. All these
may cause local floods or drought. However in India even areas that receive adequate rainfall during the monsoon
suffer from water shortages in the post monsoon period due
to lack of storage facilities.
When the quality or composition of water changes directly or
indirectly as a result of man’s activities such that it becomes
unfit for any purpose it is said to be polluted.