THE WATER TABLE

As water infiltrates gravity draws it as far as possible downward.  There is som average surface below which gravity keeps the pores of a sediment (or any other type of porosity) saturated with water except during extreme drought.  This is called the ZONE OF SATURATION.  Above this water is only present in pores as it actively infiltrates through after a rain event.  Most of the time at least part of the pore space here is air-filled and so this is the ZONE OF AERATION.  The boundary between these two zones is the WATER TABLE.  The picture summarizes this.

The lower part of the zone of aeration may continually have a thin film of water clinging to the pore walls/grain edges because surface tension of the water pulls it upward along those boundaries.  This is called the CAPILLARY FRINGE.

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