In order to study the origin of the salinity and the salinization mechanisms that operate in the Pliocene Aloha Aquifer, hydrochemical and isotopic environmental techniques have been used, due to their known effectiveness and usefulness in the identification of water-rock interaction processes, location of recharge zones and its origin. Analyzing major ions, trace elements, ionic ratios and isotopic ratios of the elements of the water molecule, stable isotopes (δ 18 O and δ 2 H) and δ 18 O and δ 34 S of sulphate. Previous hydrochemical studies of the Pliocene Aloha Aquifer indicate high concentrations of Cland Na + as well as HCO 3 , SO 4 and Ca that should be indicated the interaction with waters of highersalinity, but also with rocks (longer residence time in the aquifer). Therefore, as a starting hypothesis, two possible origins of the high salinity are considered: mixture with seawater or connate waters stored in Pliocene formations. Finally, the study confirmed that the salinity of the Aloha Aquifer is of a localcharacteristic and not due to seawater intrusion.