Hydrogeochemistry of Groundwater in a Part of the Hard Rock Terrain of Central India

Hydrogeochemical investigations have been carried out to determine the sources of dissolved ions in groundwater in a part of the hard rock terrain of central India. The high concentration of SiOl-and various geochemical signatures reflect the weathering of minerals. The groundwater chemistry favours the formation of clay minerals due to evaporation. The positive saturation index of calcite and the higher ratio of Mg/Ca and Na/Ca also support the occurrence of evaporation. The evaporation enhances the concentration of ions in groundwater during the summer. The high content of sulphate and chloride in some groundwater, and the occurrence of kankar in the area suggest a long history of evaporation. Greater ion concentrations in the groundwater of the post-monsoon period compared with the pre-monsoon period indicates the increasing addition of leachates into the groundwater from the soil and anthropogenic activities, which leads to a deteriorating quality of groundwater. The Gibbs diagram shows that the groundwater chemistry is controlled by rock weathering to some extent and that evaporation is a dominant factor leading to the deterioration of the quality of groundwater in the area.