Water is necessary for life. All organisms contain it, some drink it
and some live in it. Plants and animals require water that is
moderately pure and they cannot survive if water contains toxic
chemicasl or harmful microorganisms. Water pollution kills large
quantity of fish, birds, and other animals, in some cases killing
everything it affects. So it is very important to have clean water. Water
pollution occurs mostly, when people overload water sources such
as streams, lakes, underground flows, bays or seas with waste or
substances harmful to living beings. Pollution makes streams, lakes and
coastal waters unpleasant to swim in or to have rest. Fish and
shellfish harvested from polluted waters may be unsafe to eat. People
who consume polluted water may get ill if they drink polluted water for a
long time.