• The introduction of any type of foreign materials into natural water to reduce the biodiversity of aquatic life may be regarded as water pollution.
• Water pollution is caused due to run off of wastes from kitchen, industries, and mines; agricultural wastes and pesticides; radioactive substances, and sewage.

Factors that contribute to water pollution can be categorized into two different groups

a) Point sources

b) Non-point sources

Point sources are the easiest to identify and control whereas non point sources are ambiguously defined and harder to control. Some point sources of water pollution include

a) Waste products from factories

b) Waste from sewage system

c) Waste from power plants

d) Waste from underground coalmines

e) Waste from oil wells

The term non-point source encompasses a large range of sources such as:

• when rain or snow moves through the ground and picks up pollutants as it move towards a major body of water
• the runoff of fertilizers from farm animals and crop land
• air pollutants getting washed or deposited to earth

• storm water drainage from lawns, parking lots, and streets