Hydrogeochemical Characterization of Groundwater in and around Rajahmundry, Andhra Pradesh, South India

Groundwater quality assessment is critical for ensuring sustainable water resources in rapidly urbanizing regions. This study evaluates the hydrogeochemical characteristics and water quality of groundwater in and around Rajahmundry, Andhra Pradesh, South India, an area influenced by both natural geological processes and anthropogenic pressures. A total of 151 groundwater samples were collected during pre- and post-monsoon seasons and analyzed for major ions using standard APHA procedures. Hydrochemical facies were identified through classical graphical methods (Piper, Durov, Chadha, Schoeller, Gibbs, and Gaillardet plots) and supported by statistical clustering. The results reveal that the groundwater is predominantly of calcium–magnesium–bicarbonate (Ca–Mg–HCO₃) type, indicating dominance of rock–water interaction, particularly carbonate weathering, as the primary hydrogeochemical process. Both pre- and post-monsoon datasets showed minimal seasonal variation, suggesting a stable aquifer system with strong geogenic control and high buffering capacity. Gibbs and Gaillardet plots confirm rock-weathering as the major mechanism governing groundwater chemistry, while Schoeller plots highlight the consistency of ion concentrations across the study area.