Hydrogeology of thermal waters. A case stydy in Portugal

Abstract

The main purpose of this work was to investigate the cause(s) of the loss of sulfur observed in one of the existing groundwater wells in Termas da Fonte Santa, county of Almeida, region of Guarda. It was carried out a characterization of the thermal waters, in particular the alkaline sulfur ones, in which the waters of the wells under analysis are inserted. Then, the area under study was characterized from a geographical, geomorphological and geological-structural point of view. After some brief historical considerations about these wells, it was undertaken a survey of the characteristics of the aquifer. The existing wells in the area were described, in particular the FS2 and AQ1 ones, as well as the hydrochemistry of the respective waters. A multiplicity of statistical treatments was carried out to investigate the problem of the loss of sulfur at the FS2 well. It was given particular emphasis to the application of the Principal Component Analysis (PCA), as a data processing method which, in the multivariate statistics scope, seeks a multidimensional understanding of the phenomenon under study, being analysed the eventual relation of all hydrochemical variables in the general behavior of the considered hydrogeological system. With this study it was possible to recognize the vital importance of such relevant aspects as the efficient isolation of the wells, the consideration of the fracturing state of the surrounding massifs or the influence of the regionŽs climate on the proper functioning of the well.