Hydrogeochemical characteristics of Karst Aquifer from a semi-arid region of Southern India and impact of rainfall recharge on groundwater chemistry

Abstract : he highly heterogeneous and anisotropic property of karst aquifers is a result of the dissolution and karstification of carbonate rocks. Hydrogeochemical evolution and possible water–rock interaction is therefore discussed through spatial and temporal variations in physico–chemical variables of groundwater. Samples were collected both from spring and bore wells. Dissolution of carbonate minerals is the main source of major ions (Ca2+, Mg2+ and HCO3−) in the water. Agricultural activities cause an increase in the concentration of pollution-related ions (nitrates, sulphates, chlorides, etc.). The variability of water chemistry was discussed in terms of different processes like dilution and water–rock interactions, etc. The study reveals a pronounced seasonal hydrochemical variation in the limestone aquifer. In general, the karst groundwater is of Ca–Mg–HCO3 type. Hydrogeochemical signature also helped to analyse the recharge types in the area. The semi-arid climate of the area also contributes to the increase of concentration of certain ions.