Hydrogeochemical characteristics of groundwater in a mid-western coastal aquifer system, Korea

Hydrogeochemical characteristics of shallow groundwater in a mid-western coastal aquifer system, Korea have been investigated to identify the salinization process. The spatial distributions of the groundwater components are well consistent with the groundwater flow pattern that follows topography in the study area. The groundwater at many locations in the study area is not suitable for drinking water because of its high salinity, which is mainly caused by seawater intrusion. The chemical composition of the groundwater is characterized by high chloride concentration and high variations in cation concentrations due to the cation exchange reaction between aquifer minerals and seawater components. The similar distributions of chemical components between rainy and dry seasons suggest that the groundwater flow system is almost in a steady state condition. The groundwater is classified into Ca(HCO ₃)₂, CaCl₂, and NaCl types based on its hydrogeochemical characteristics. The groundwater from the alluvial aquifer shows higher salinity in the rainy season than the dry season while the groundwater in the bedrock aquifer shows lower salinity year-round. Isotope data and factor analysis also indicate that the hydrogeochemical characteristics of groundwater are not only influenced by seawater intrusion but also by agricultural activities.