This presentation by ACWADAM explains the occurrence of groundwater and deals with the vertical distribution of groundwater. To begin with, the openings in rocks in the zone of rock fracture such as intergranular openings, vesicles in volcanic rock, joints & fractures and solution cavities are described.

The portion of rock below the zone of rock fracture is very dense and may contain isolated openings. This zone of dense rock generally has no openings that can hold significant quantities of water. The zone of rock fracture shows variable thickness and depends upon type of rock and geological conditions within a single rock type. The zone of aeration and zone of saturation within the zone of rock fracture is described. The forces at work in the zone of aeration - adhesion, cohesion and capillary action are explained. 

The presentation also deals with the following -

• The uppermost surface of the zone of saturation is called the water table. The level of water in a well (shallow dugwell) penetrating the zone of saturation is the visible manifestation of the water table.
• Joining the water levels in shallow dug wells helps us trace the imaginary surface of the water table in an area.
• The water stored in the saturated zone can be readily augmented through wells and is commonly referred to as groundwater.
• The capillary fringe is an upward extension from the water table.
• The height of the capillary fringe will be greater in fine grained material such as clay.

This presentation is part of the training modules on planning, development and management of groundwater with special reference to watershed management programmes by ACWADAM. Please write to ACWADAM at acwadam@vsnl.net for sourcing these presentations.