abstract
- The dynamics of surface-groundwater interaction (SGI) in the alluvial Gangetic plains are critically analyzed using multivariate statistical techniques (MST) applied to major and trace ion chemistry of river water (RW) and groundwater (GW) samples. The study reveals an unusual decline in SGI, even in typically stable alluvial zones. A higher saturation index for RW indicates increasing risks in critical regions, suggesting disruption in natural recharge-discharge processes. Probability exceedance plot highlights an inverse relationship between contaminant concentrations and the likelihood of exceeding regulatory thresholds. RW is contaminated by both domestic and industrial wastewater, while GW remains largely unaffected, as shown by lower total organic carbon levels. Hydrogeochemical analyses indicate that RW generally contains higher levels of micropollutants such as arsenic (As) and lead (Pb) compared to GW. A novel integration of Q and R¿mode hierarchical clustering with heat mapping is applied for the first time to assess SGI in the Mid-Gangetic Plain, enabling clearer differentiation of RW and GW and revealing complex geogenic¿anthropogenic interactions. The altered ionic associations identified through MST require further investigation to understand their hydrogeochemical implications and potential risks to ecosystem health. Immediate action is recommended as rapid hydrogeologic change threatens sustainable water management.