Geochemical Modeling of Groundwater in Chinnar River Basin: A Source Identification Perspective

Abstract

Understanding the geochemical evolution of groundwater is an essential part of the performance assessment and safety analysis of the geological system. Geochemical modeling techniques using PHREEQCI will aid in demarcating the main factors and mechanisms controlling the chemistry of groundwater. An attempt has been made in hard rock terrain of Chinnar basin, Dharmapuri district of Tamilnadu, India to interpret the processes and factors controlling hydrogeochemistry of groundwater. The area is made up of rock units belonging to Charnockite and Granitic Gneiss. Groundwater chemistry has been attempted based on laboratory observations of major cations like Na+, K+, Ca2+ and Mg2+and anions like Cl-, HCO3-, NO3-, F-, SO42-and PO43−. Piper diagram reveals higher bicarbonate, calcium and magnesium along the recharge zones and tend to decrease along the flow path and vice versa for ions like sodium, potassium and chloride. Two flow paths based on piper and saturation index were identified for two major lithounits. The granitic terrain shows precipitation of calcium and sulfate minerals and dissolution of silicate minerals. The charnockite terrain shows precipitation of silicates and dissolution of calcium and sulfate minerals. From initial to final solution slight variation in calcium and sulfate stability were identified but drastic change with reference to silicate minerals stability due to effective dissolution of silicate minerals from the litho units of the study area.