The phenomenon, by which the quality of water in the hydrosphere is decreased, is called as "water pollution". Though water occupies a major portion of the earth, very little water is available for drinking. Drinking water is available in ponds, rivers, and as underground water. This is also used for cultivation. Dissolved oxygen present in water, supports the aquatic life. In short, the welfare of the people depends on the quality of water. In olden days, when the population was less, people used to perform their daily activities in the nearby lakes or ponds. Old-water was always replaced by new water. Thus, there was a little chance for the water to get polluted. With an increase in the population, industries and progress made in the agricultural sector, many unwanted substances were released into the water, due to which the quality of the water has decreased sharply.
Mode of Water Pollution
The chart below shows how water gets polluted in various ways.