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

Abstract

The current 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. Findings revealed that the major ion types in atmospheric waters are calcic and magnesium bicarbonate, whereas hydrothermal springs predominantly indicated chloride–sodic composition, showing an evolving pattern resulting from hydrothermal and atmospheric waters mixing. Investigating the ionic ratios and the saturation index to determine the origin of ions 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 in some cases, ionic exchange also plays a role. The recession curve analysis revealed a predominant 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, indicating the development of systems with two types of flow regimes. Estimating the Qmax/Qmin ratio for selected hydrothermal and atmospheric springs as 2.3 and 36.8, respectively, and calculating the electrical conductivity coefficient as 11% and 18% respectively, confirmed the recession curve analysis result. HIGHLIGHTS Determination of the origin and type of flow by investigating the hydrochemical and hydrodynamic characteristics of water flowing out through hydrothermal and atmospheric springs.; The major ion types in atmospheric waters are calcic and magnesium bicarbonate while in hydrothermal springs are chloride sodic indicating evolving water from mixing hydrothermal and atmospheric waters.; The ionic ratios and saturation index suggest that ions in waters resulted from the weathering of silicates and plagioclase-bearing minerals in the volcanic units.; Evaluation of maximum to minimum discharge and EC variation confirmed the type of flow system defined by the recession curve.; The recession curve analysis and type of flow regime revealed that atmospheric springs originate from precipitation while hydrothermal springs result from atmospheric and hydrothermal waters mixing.;

Keywords

• atmospheric and hydrothermal springs
• hydrochemistry
• hydrodynamic analysis
• saein basin