Abstract:
Water is a truly amazing resource on Earth that
nature offers us absolutely free of charge, and it is ranked
second only to oxygen as being essential for life. More
than 70% of the Earth’s surface is covered with water.
However, fresh water comprises only 2.5% of the total
water content on Earth and the rest is too salty to use.
From the available fresh water content, less than 1%
is easily accessible for Earth’s biota. These accessible
fresh water sources are streams, lakes, reservoirs and
underground sources.