The addition of external and unwanted material in natural water which reduces its quality is called water pollution. 

Causes of water pollution :

1. Effluents coming out of factories. 

2. Sewage water contains several harmful material and uric acid and microbes. 

3. Nitrate and phosphate salts are used as fertilizers in the field. These salts mixing with soil and rainwater pollute the water. 

4. Crude oil, at the time of extraction mixes in rainwater and pollutes the water sources.

Effects Following are the effects: 

1. Diarrhoea, dysentery, cholera, typhoid, etc diseases are caused by the use of polluted water. 

2. By mixing of dangerous chemicals in water, animals living in water die. 

3. When man comes in contact of polluted water, several parasites enter in his body and cause the deceases like ‘Naru’ 

4. Chemical materials, present in water, cause several disease like small pox.

5. In polluted water different pollutants accumulate on the water surface and destroy floating plants.

Measure to Check Water Pollution : 

Following are the measures : 

1. Use of chemical soap should be stopped. 

2. Use of excess chemicals, fertilizers should be stopped and organic manure should be used. 

3. Radioactive material and hospital wastes should be buried into the earth instead of throwing them on garbage heaps or water. Before mixing into river water, the organic and inorganic materials should be destroyed from industrial wastes. 

4. The domestic sewage should not be mixed directly into water. 

5. The water of sewage and gutter should be treated in treatment plants and should be used in irrigation or other works.