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CHAPTER - VI
GROUNDWATERRESOURCES
Groundwater hydrology may be defined as the science of the occurrence,
distribution and movement of water below the surface of the earth (Todd, 1959).
We refer frequently to "geohydrology" and "hydrogeology" to connote the same
as defined above. Hydrogeology, however, gives more emphasis on geology,
while "geohydrology" gives more importance to hydrology. The subject
essentially is an earth science and encompasses within its domain geology,
mathematics, fluid mechanics, soil science, meteorology, oceanography,
chemistry etc. When we think on a broader perspective including utilization and
applied aspects, we are to include civil, mechanical, agricultural and electrical
engineering in its domain. Civil Engineers, Agricultural Engineers and
Geologists are the generally professional groundwater scientists.
What is Groundwater ?
Literally, it means water that occurs below the ground surface. Surface water
infiltrates into underground through suitable geological formations and its
vertical flow continues until it reaches the zone of saturation, below which the
entire permeable geological formation is saturated with water i.e. all the
interstices are filled with water under hydrostatic pressure. The zone above the
zone of saturation is the zone of aeration where the interstices of soil particles
are filled with water and air. The upper surface of the imaginary line between the
zone of saturation and the zone of aeration is known as water table. The
pressure on the water table is the atmospheric pressure. In certain geologic
conditions, the upper surface of the zone of saturation may be an impermeable
layer and the pressure on the saturated zone may be more than the
atmospheric pressure and a well or a tube piercing this zone may experience
the rushing out of water through a tube to the surface (artesian condition). The
upper surface of this pressure zone is known as "piezometric surface". Water
occurring in the zone of saturation is "groundwater" commonly used by us.
Groundwater occurring under atmospheric condition is known to be water table
