INTEGRATION OF GIS, ENTROPY WEIGHTING, AND THE GROUNDWATER QUALITY INDEX (GWQI) FOR ASSESSING GROUNDWATER QUALITY ON PHU QUOC ISLAND, AN GIANG PROVINCE
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Abstract
With ongoing socio-economic development, water demand on Phu Quoc Island has been steadily increasing. While surface water resources are insufficient to meet this demand, groundwater has not yet been comprehensively assessed, particularly in terms of quality. This study integrates GIS, the entropy weighting method, and the groundwater quality index (GWQI) to evaluate groundwater quality on Phu Quoc Island, based on Vietnamese water quality standards and those of the World Health Organization (WHO). The results indicate that the groundwater is predominantly of the Na–Cl type and generally exhibits good quality, with most parameters falling within permissible limits. Among the twelve parameters used in the GWQI calculation, pH shows the highest entropy weight. The GWQI results reveal that groundwater quality ranges from good to very good. These findings suggest that groundwater on Phu Quoc Island is generally suitable for domestic use, while also highlighting the objectivity of the entropy method in groundwater quality assessment.