ABSTRACT
Rising sea levels, groundwater exploitation, and urbanization were the primary causes of seawater intrusion, exerting pressure on coastal aquifers. In Sri Lanka's urban coastal region, a comprehensive physicochemical description of groundwater has yet to be identified. Therefore, the objectives of this research were to (a) use a Geographic Information System (GIS) to designate spatial distribution of various water physicochemical characteristics, (b) detect "suitable" groundwater zones for drinking, and (c) estimate groundwater quality by developing a groundwater quality index (GWQI) in Sri Lanka's urban coastal region. The physiochemical parameters of 18 groundwater samples [pH, electrical conductivity (EC), turbidity, total dissolved solids (TDS), Na+, K+, Ca2+, Mg2+, Cl-, and HCO3-] were studied in terms of their spatial and temporal variation. According to the World Health Organization (WHO) and Sri Lankan Standard Institution (SLS), EC levels in 11% of samples were above the acceptable range, while turbidity levels in 22% of samples were above the acceptable range. Water was consumable in 77.78% of the locations and unsatisfactory in 22.22%. The main hydrochemical facies detected in groundwater samples were Na+- Cl- and the mixed Ca2+- Mg2+- Cl- face, which indicated carbonate dissolution and weathering of silicate minerals and the main mechanism controlling the water chemistry in the study area is water-rock interaction. Based on daily water consumption, it was discovered that the HQ is greater than one, in 61% of males, 78% of females, and 89% of children, indicating a health hazard. Furthermore, groundwater quality in the study region is deteriorating due to significant coastal erosion, making it critical to maintain a comprehensive groundwater management strategy to promote sustainable water consumption.
