Water is one of the most necessary things to life on earth. All organisms need it, some of them drink it and some live in it. Animals and plants need moderately pure water and they cannot live if water is loaded with harmful microorganisms or toxic chemicals. Polluted water can kill large numbers of birds, fishes and other animals and in few cases killing all the species in a affected area.

Pollution makes unpleasant to look at, lakes, streams and coastal waters to smell and to swim in. Fish and other sea foods harvested from polluted water may be unsafe to eat. People who intake polluted water can become ill and if they continue it for long time, may develop cancers or their may result it birth defects.

Point source and non-point source are two types of water pollution. Point source pollution occurs when harmful substances are directly put into a body of water, like an oil spill. Non-point source occurs when pollutants through environmental changes enter the water indirectly.