After glaciers, ice caps and snowfields, ground water is the next largest fresh water reservoir. Precipitation that does not evaporate back into the air and does not run off over the surface penetrates through the soil and accumulates as underground water. Ground water is located in the pore space of soils and rocks and is the major source of fresh water for agricultural and domestic use. We can obtain it through tube wells, wells, aquifers etc.
Characteristics of ground water:
Ground water is generally rich in mineral content as large number of salts is dissolved in it when it percolates down. It may contain high iron contents also. The quality of ground water is generally uniform. In surface water it is relatively free from suspended impurities because they are filtered as the moves down through the different layers of soil. The filtration also removes most of the biological contamination.