Influence of Short-Term Climate Extremes on Surface Water-Groundwater Interaction: A Regional Perspective on Drinking Water Vulnerability

Coastal aquifers are hydraulically connected to the sea, making them highly sensitive to storm-induced disturbances; however, the impacts of tropical cyclones on surface water-groundwater (SW–GW) interactions remain poorly understood. This study has investigated the impact of short-term climate extremes specifically cyclone-induced storm surges on coastal aquifer systems along India’s eastern coastal regions in Nizampatnam Andhra Pradesh (Tropical cyclone Dana, May 2024) and in Sundarbans of Ganges delta front (Tropical cyclone Bulbul, November 2019) adjoining to Bay of Bengal. The study has incorporated a field-laboratory, isotopic, and multivariate statistical observations-based approaches to assess and compare the influence of storm-driven impacts on groundwater level (GWL) and displacement of toxic solutes in porewater which eventually hampered the SW-GW interaction processes across the regions. Results revealed a positive relationship between cyclonic translation speed, rainfall intensity, and GWL response, especially in lithologically conductive aquifers. In Sundarbans, the storm surge was associated with increased GWL, enhanced salinity, and the downward transport of surface-derived contaminants into groundwater. In addition, wave surges produced instantaneous, rapid, and synchronous GWL fluctuations across all aquifer depths in Sundarbans. Whereas in Nizampatnam, cyclone-induced atmospheric pressure decline and storm surge caused transient offshore displacement of the SW–GW interface, enhancing fresh groundwater discharge, as indicated by depleted δ¹⁸O elevated ²²²Rn, and reduced salinity. The duration of SW–GW system re-stabilization varies widely from weeks to several years and is strongly controlled by local hydrogeological conditions and storm intensity. Therefore, the findings highlight the growing vulnerability of coastal groundwater resources under increasing storm frequency and intensity, emphasizing the need for proactive management strategies to ensure freshwater sustainability to achieve SDG-6 in a changing climate.

Keywords: Coastal aquifer; Groundwater Level; Porewater; Tropical Cyclone; SW-GW Interaction; SDG-6