Water pollution is caused by chemical and industrial waste, agricultural waste, trash, mining activities, waste and sewage water, accidental oil leakage, marine dumping and energy use. Many kinds of human activities cause water pollution, making it a complex problem.
Water pollution refers to the contamination of natural sources of water such as groundwater, streams, rivers, lakes and oceans due to the introduction of contaminants directly or indirectly into these waters. Polluted water can have serious negative effects to the health of any organism that lives in or drinks this water.
As a major global problem, water pollution is known to be the leading cause of diseases and deaths worldwide, accounting for more than 14,000 deaths daily. Since water comprises about 70 percent of the surface of the earth, it's often called the most valuable natural resource on earth.
There are two ways in which water pollution occurs: point-source and nonpoint-source. If pollution originates from a single, specific location, it is called point-source pollution. Examples include a factory chimney discharge, an oil leakage from a tanker, a discharge pipe connected to a factory or a person pouring oil from a vehicle down a drain.
Pollution that comes from many different sources is known as nonpoint-source pollution. Examples of this include traffic pollution, acid deposition in the air and pollutants that enter water through rivers and groundwater. This type of pollution is more difficult to control as the sources cannot be traced.