GIS-Based Modeling Approach for Analysis of Groundwater Quality in the Dry Zone of Sri Lanka

Groundwater is a vital resource in Sri Lanka's dry zone, where limited rainfall and surface water make communities heavily dependent on groundwater for daily needs. This study assesses groundwater quality in the region using a GIS-based modeling approach that integrates the Analytic Hierarchy Process (AHP) and Multi-Criteria Decision Analysis (MCDA). Six key groundwater quality parameters, pH, Electrical Conductivity (EC), Total Dissolved Solids (TDS), Alkalinity, Hardness, and Fluoride, were used to develop thematic layers via the Inverse Distance Weighted (IDW) interpolation method in ArcGIS 10.4. These layers were classified based on World Health Organization (WHO) drinking water standards. Using MCDA, proportional weights were assigned to each parameter and corresponding feature class. The results reveal that groundwater quality is suboptimal in parts of the study area: 16.75% of areas fall under moderate quality, while 4.37% are categorized as unsuitable water quality. These statistical methods were employed to enhance understanding of the interrelationships among water quality parameters. Multivariate statistical techniques, Principal Component Analysis (PCA), K-means Cluster Analysis, and Correlation Matrix analysis were employed to support the analysis further. A notable negative correlation was found between EC and TDS with pH (r = -0.14), while alkalinity and hardness exhibited a strong positive correlation (r = 0.98). These findings underscore the effectiveness of geospatial methods over traditional techniques in assessing spatial variations in water quality. The results provide valuable insights for planners and policymakers to improve water resource management in Sri Lanka’s dry zone.