Based on the study of ionic relationships, ionic deltas and mineral saturation indices, it was possible to elucidate the main processes that condition the chemical composition of each of these groups of samples. The most important among said processes is the dissolution of dolomite or dolomitic limestone, the primary component of the aquifer rock. Compositional changes are due to SO42- concentration resulting from gypsum dissolution (G2). In G3, salinity is the result of dissolution of salts, or contamination through saline waters of the upper detrital aquifer. Seawater intrusion, a consequence of the overexploitation of the aquifer, increases the salinity in the G4 samples. In this intrusion process, waters of marine origin rich in Mg, interact with the carbonated rock, favouring a cation exchange in which Mg is fixed in dolomite or dolomitic limestone and Ca ion is released. This process is supported by the ionic delta values of these two cations. The marine intrusion in the area is facilitated through groundwater overexploitation, and also by the structuring of the aquifer. Marine intrusion exists where tectonics has allowed interconnection between the carbonate rock and the sea. In other areas on this coast, marine intrusion has not been possible because of the presence of impermeable Neogene materials that prevent this interconnection.