Definition The term phreatic is used in geology to refer to matters relating to ground water below the static water table (the word originates from the Greek phrear, phreat- meaning "well" or "spring"). "Phreatic surface" is a synonym for "water table." The phreatic zone is the layer(s) of soil or rock below the water table in which voids are permanently saturated with groundwater, as opposed to the higher vadose zone in which the pore spaces are not completely filled with water. Phreatic actio… (More on Phreatic)