Abstract

Pleistocene aquifer is exploited for many purposes, including irrigation, domestic, production, and livestock use in Phu My town, Ba Ria – Vung Tau province. Groundwater Quality Index (GWQI) method combined with Geographic Information System (GIS) foundation is applied to determine the spatial variation as well as the suitability of groundwater in the study area. Water quality parameters in this study include pH, TDS, total hardness, Cl^-, F^-, NH₄⁺, NO₃^-, SO₄^2-, Pb^2+, and Fe²⁺ were selected for analyzing from 17 monitoring wells in dry and wet seasons in 2017. The results indicate that water quality parameters such as Cl^-, F^-, NH₄⁺-N, Pb²⁺ và Fe²⁺ exceed the maximum allowable levels by National Technical Regulation on Groundwater Quality. The groundwater quality, according to GWQI analysis results, shows that indicate 88% and 94% of the monitoring wells are from “good” to “excellent” type in the dry and wet seasons, respectively. The number of wells that have water quality from “poor” to “water unsuitable for drinking purpose” varies between the dry and wet seasons. Corresponding with the GWQI map, it shows that the area with good quality groundwater accounts for 98% of the total study area (331.44 km²) in the dry season and 94.5% of the study area (319.58 km²) in the wet season.