Ground Water Sources:

Water precipitated upon the surface of the earth is disposed off in three ways - by evaporation, by surface flow and by percolation.

Percolating water that passes beyond vegetation passes on downward in obedience to the law of gravitation until it reaches an impervious layer of some kind. The accumulation of water which exists in the ground is called ground water and its top is known as ground water level or ground water table. The volume of water stored in any soil/rock strata depends mainly on porosity (i.e. maximum water storage capacity) and permeability (which determines the ability to transmit water through itself) of rock/soil strata.

To obtain large quantity of water economically, it is necessary that water bearing strata be of open and porous character. The sand and gravel deposits possess high porosity as well as permeability, hence they are considered as most favourable formations for furnishing large quantity of water for public water supply schemes. The clay is highly porous but more impervious (practically nil permeability), whereas lime stone and dolomite possess medium porosity but contain water only if fissured.