Groundwater Quality Assessment Using Water Quality Index, Principal Component and Cluster Analyses: A Case Study

Abstract

This study assessed groundwater quality in Can Tho city, Vietnam using groundwater quality index (GWQI), principal component analysis (PCA), and cluster analysis (CA). Groundwater samples were collected in April (dry season) and October (rainy season) in 2019 and then analyzed for thirteen parameters: pH, color, total hardness, chloride, sulfate, chemical oxygen demand, magnesium, total iron, nitrate, arsenic, lead, mercury, and coliforms. The results showed that the values of these parameters were mainly within the Vietnamese regulations on groundwater quality, except for coliform density. Computed GWQI values in all monitoring sites were lower than 50 and suitable for potable purposes. The GWQI values in the dry season were slightly higher than in the rainy season because of higher concentrations of Cl-, SO42-, COD, As, Pb, and coliforms in the southeast of Can Tho. The results of CA revealed that 27 monitoring sites can be divided into nine clusters in the dry season and five clusters in the rainy season, which means that more noticeable spatial variation in groundwater quality occurred in the dry season. The PCA results can explain 63.4% and 73.9% of the total variation in the dry season via 4PCs and in the rainy season via 3PCs, respectively. It also indicated that this water resource could be affected by different sources such as industrial and agricultural activities, domestic wastewaters, and saltwater intrusion. These findings can be useful for policymakers in assessing current groundwater status and recognizing threats to its quality, and then developing long-term management policy.