### Theory:

Water covers roughly around $$71\%$$ of the earth's surface, which is why the earth is termed the water planet or blue planet. Water is an essential element of all living things. It is also the $$second$$ most abundant substance in the earth's biosphere after the air. Oceans, seas, and other saline inland water bodies account for $$97.3\%$$ of the total global water supply that is not suitable for human consumption due to high salinity. Only $$2.7%$$ of the entire estimated global water supply is freshwater.

Earth's water cover

Of this, $$75\%$$ of the freshwater on the planet is frozen in polar ice caps and glaciers. There is some freshwater present under the ground. The amount of freshwater available to humans is less than $$0.003\%$$ of the total amount of water available on the planet. Freshwater is available from $$three$$ primary sources, including:

i. Rainwater

ii. Surface-water - rivers, ponds, lakes, and streams

iii. Groundwater

Earth's water distribution

The first is India's rainwater resource. India receives roughly $$105$$ to $$117\ cm$$ of rain every year, resulting in $$3\ million^3$$ of water. Rains in India are due to the monsoons, and most of the rainwater is collected in that season (few months of the year).

Surface water is the second source. There are $$14$$ major rivers, including the Ganga, Brahmaputra, Godavari, Krishna, Cauvery, etc. Ponds, lakes, and streams are examples of other surface water sources.

Groundwater, the water the that percolates down the surface soil into the pore spaces of rocks, is the third source. Groundwater provides soil moisture for the growth of plants. The agricultural and urban water supply sectors utilise the groundwater. Thus, the groundwater level is declining in the groundwater aquifer.

Groundwater source
Reference:
https://commons.wikimedia.org/wiki/File:Earth%27s_water_distribution.svg