The study area is in the northern central part of Crete Island (municipally of Chersonisos) and is formed by limestones of the Tripoli zone. This aquifer lies between a distance of 0,7 Km from the coast and the mountainous area, and it is in direct hydraulic continuity with seawater in the western part of the border area. The Tripoli series consist of faulted and karstfied Upper Triassic-Upper Eocene age thickheaded limestones, dolomites and calcareous dolomites, showing high permeability due to theyr well developed wide jointing and karstfication (Alexopoulos, 2001). The Phyllite-Quartzite series form the impervious basic layer.