1.  Introduction

Groundwater is the primary source of drinking and domestic water supply in Bangladesh, particularly in rural and coastal regions where surface water is scarce or heavily polluted (Ahmed, 2003). The increasing population, economic activities, and seasonal variability of surface water have led to a growing dependence on groundwater resources. In southwest Bangladesh-where Satkhira district is located groundwater plays an essential role in sustaining agricultural practices, domestic consumption, aquaculture, and small-scale industries (Das, 2021).

Kaliganj upazila, situated within the coastal belt of Satkhira, experiences distinctive hydrogeological challenges shaped by saline water intrusion, tidal surges, storm surges, and the impacts of climate change (Haque et al., 2024). Due to its proximity to the Bay of Bengal and low elevation, the region is highly vulnerable to salinity contamination of groundwater, which is exacerbated by sea-level rise and reduced freshwater inflow from upstream river systems. Furthermore, cyclones such as Aila, Sidr, and Amphan have intensified salinity intrusion into both surface and groundwater systems (Rasheed et al., 2019). Human activities further contribute to groundwater quality deterioration. Practices such as unplanned shrimp culture, overuse of agrochemicals, and improper waste disposal have increased the presence of contaminants like nitrates, phosphates, and heavy metals in aquifers (Hussain et al.,2015). In Satkhira, groundwater studies show elevated concentrations of sodium, chloride, and total dissolved solids (TDS), making water unsuitable for drinking without treatment (Das, 2021).

Other coastal studies reveal widespread risks from arsenic, microbial contaminants, and salinity, threatening both public health and crop productivity (Rahman et al., 2019). Poor groundwater quality has multidimensional consequences. High salinity intake through drinking water has been associated with hypertension, pre-eclampsia, and pregnancy complications in coastal communities