Impact of 2018 Climate Extreme on Groundwater Quality: Assessment of Environmental Pollution and Health in Periyar Basin, Southern Western Ghats, India

ABSTRACT The increasing frequency and intensity of climate extremes such as heavy rainfall, tropical cyclones, and large-scale flooding are key manifestations of Anthropocene-driven climate change, with profound impacts on Earth system processes. These disruptions have heightened the prevalence of climate-sensitive diseases and intensified environmental contamination, particularly in tropical regions. This study examines the influence of the 2018 Kerala floods on groundwater quality and associated public health risks in the Periyar River Basin (PRB), a low-lying region with a shallow water table vulnerable to rapid floodwater infiltration. Groundwater samples (n = 47) were collected across four hydrological phases: pre-flood, flood, and post-flood periods of 2018, and a non-flood period in 2021. Analysis revealed that 69% of wells experienced improved water quality post-flood, 19% showed deterioration during the flood compared to pre-flood conditions, and 12% exhibited negligible change. In 2021, degraded water quality was observed in 15% of samples during the pre-monsoon and in 11% during the post-monsoon period. Health data analysis indicated a peak in diarrheal illnesses prior to the flood, correlating with Escherichia coli concentrations reaching 760 CFU/mL likely due to infiltration from septic systems or compromised sewage infrastructure. Following flood response measures such as systematic well disinfection and chlorination, E. coli levels declined to 280 CFU/mL. The findings highlight the vulnerability of shallow aquifers to climate-induced flooding and emphasize the critical need for integrated water quality monitoring and post-disaster sanitation interventions to mitigate microbial and chemical contamination in groundwater.