Water covers two-thirds of the Earth’s surface, with over 97% present in the oceans and less than 1% in freshwater streams and lakes. Water is also present in the atmosphere in solid form in the polar icecaps and as groundwater in water-bearing rocks deep underground. Water is called a universal solvent because many things get dissolved in it.
Water pollution may be defined as any chemical or physical change in water, harmful to living organisms. It can occur through natural processes. For example, water can be polluted by sediments produced by natural erosion. Water bodies get polluted as they receive a lot of waste produced by human activity. This waste is discharged directly into the water bodies by sewers or pipes from factories and washed down from agricultural or urban areas, especially after heavy rains.
Sources of pollution may be domestic, agricultural or industrial. In the underdeveloped and developing countries human and animal waste and sediments from defective agricultural and forestry practices are the main pollutants. In developed countries, industrial pollutants such as toxic metals and organic chemicals add to the water pollution. This is more dangerous than the pollution caused by human and animal waste.
Water pollution is caused by dierent things. They include excessive plant nutrients, acidification by acid rain and acid mine drainage, organic compounds containing chlorine like DDT and other pesticides, oil getting into water sources through drilling or accidental spillage from oil tankers, the discharge of huge quantities hot water into water bodies causing thermal pollution, fluoride and arsenal pollutants. Now the question comes how can we prevent water pollution? If the water is polluted people and animals easily become sick and die. But we can do certain things to prevent or reduce pollution. First of all industries should not be allowed to discharge untreated chemicals into water bodies, especially rivers and lakes.
Secondly, the domestic sewage system should be designed in a scientific manner. Thirdly, Underground water can be saved from pollution if the land is not exposed to pesticides and other industrial chemicals. Farmers should be encouraged to do organic farming instead of using a lot of artificial fertilizers, pesticides and other such things that pollute the soil and later get washed into the water bodies.
