Classification of thermal waters based on their inorganic fingerprint and hydrogeothermal modelling

Abstract. Hydrothermal features in Galicia have been used since ancient times for therapeutic purposes. A characterization of these thermal waters was carried out in order to understand their behaviour based on inorganic pattern and water-rock interaction mechanisms. In this way 15 thermal water samples were collected in the same hydrographical system. The results of the hydrogeochemistry analysis showed one main water family of bicarbonate type sodium waters, typical in the post-orogenic basins of Galicia. Principal component analysis (PCA) and partial lest squared (PLS) clustered the selected thermal waters in two groups, regarding to their chemical composition. This classification agreed with the results obtained by the use of geothermometers and the hydrogeochemical modelling. The first included thermal samples that could be in contact with surface waters and therefore, their residence time in the reservoir and their water-rock interaction would be less important than for the thermal waters of the second group.