Assessment of groundwater quality in Vavuniya and Mullaitivu, Sri Lanka using multivariate statistical techniques and a Water Quality Index

Abstract

Groundwater is the primary source of potable water in the Northern province of Sri Lanka. Extensive development projects, comprising resettlements after the civil war, resulted in more groundwater extraction. This study focused to assess water quality considering drinking by developing a Water Quality Index (WQI), applying Hierarchical Cluster Analysis (HCA) and Principal Component Analysis (PCA), and developing spatial distribution maps. Findings revealed more than 50% of samples reported total dissolved solid (TDS), hardness, and alkalinity values above the Sri Lankan drinking water quality standards (SLS 614:2013). 7 and 13% of sampling sites were in the ‘Excellent’ and ‘Poor’ subclasses, respectively. PCA results explained >77% of variability by the first four principal components (PCs). PC1 and PC2 reflect geogenic processes while PC3 reflects natural processes like high rainfall and PC4 indicates anthropogenic pollution sources. HCA rendered 122 sampling sites into three clusters. An integrated map of the WQI and three clusters discovers a predominant analysis of potable water quality, highlighting the deterioration of groundwater quality mainly in the study area's 18 Grama Niladhari Divisions (GNDs). Artificial recharging at the household level and introducing proper sanitation facilities and regulations in agricultural practices shall be implemented to improve the WQI further.