Geochemistry of thermomineral waters in the overexploited Alto Guadalentín aquifer (South-East Spain)

The hydrochemical study of Alto Guadalentín aquifer shows an unusually high bicarbonate content between 15 to 35 mmol l−1 and PCO2 between 0.044 to 1.289 bars and, in accordance with electric geophysical data, he is in relation with horst areas. The waters have temperatures between 19 to 32°C and conductivity between 1087 and 6810 μS cm−1 (which increased in zones with high exploitation) and are fundamentally sulphate and chloride types. Chemical equilibrium modelling shows that the waters are oversaturated in quartz, calcite and dolomite and undersaturated in anhydrite and gypsum. 18O, 2H and 13C isotopes revealed that there is an enrichment in 18O and mixing processes between meteoric waters and deep circulating waters.