Zone of Aeration

The zone of aeration, or vadose zone, is the unsaturated ground above the water table, where pore space holds both air and water and pressure is below atmospheric. It overlies the saturated phreatic zone, and the two meet at the water table. On sandy coasts this zone sits in the beach and dune above the beach water table, and its thickness oscillates with tide and wave run-up. The position of the beach water table relative to the swash controls infiltration versus exfiltration, which influences swash asymmetry, sediment deposition on the foreshore, and beach accretion or erosion. It is the medium through which a saltwater wedge meets fresh groundwater near the coast.