Hydrochemical and hydrodynamic studies to explore the origin of water in a volcanic aquifer

Abstract

This research aimed to determine the origin of ions and the type of flow system in groundwater flowing out through two types of atmospheric and hydrothermal springs by hydrochemical and hydrodynamic approaches in a volcanic aquifer. The indings revealed that the major ion types in atmospheric waters are calcic and magnesium bicarbonate, whereas hydrothermal springs predominantly have a chloride-sodic composition. It shows an evolving pattern resulting from the mixing of hydrothermal and atmospheric waters. Investigating the ionic ratios and the saturation index helps to determine the origin of ions, which suggests that the presence of ions in the waters can be attributed to the weathering of silicates and plagioclase-bearing minerals in the volcanic units and the ionic exchange in some cases. The results of the recession curve analysis revealed a predominance of conduit flow with α = 0.144 in the system feeding the representative hydrothermal spring. Two micro-regimes with α1 = 0 = 0.46 and α2 = 2.68 were detected on the hydrograph of the atmospheric representative spring, which indicates the development of systems with two types of flow regimes. The Qmax/Qmin ratio for selected hydrothermal and atmospheric springs was 2.3 and 36.8, respectively, and the calculation of the electrical conductivity coefficient confirmed the result of rescission curve analysis, with values of 11% for hydrothermal springs and 18% for atmospheric springs, respectively.