Assessing groundwater vulnerability and addressing salinization in the coastal region of Ba Ria–Vung Tau province, Vietnam: an enhanced DRASTIC model approach

For coastal areas, groundwater aquifers’ salinization has intensified due to multiple reasons, e.g., climate changes, continuous groundwater exploitation, and other anthropogenic activities. In Ba Ria–Vung Tau province, the Pleistocene aquifer is an essential source of water supply for drinking, agriculture, and industrial purposes. Thus, a groundwater vulnerability assessment was required. The objective of the study is to estimate groundwater vulnerability against salinization by applying the modified DRASTIC models with geographic information system (GIS). The modified DRASTIC models, which combine the original DRASTIC model with anthropogenic factor (land use). In addition to that, Entropy method (EN) was used to reassign the factor weights of the original DRASTIC model to improve the consistency of the conventional model with the actual conditions of the study area. The total dissolved solid (TDS) data collected from 31 monitoring boreholes was applied to validate the groundwater vulnerability assessments. The results show that around 0.97%, 84.94%, and 14.09% of areas fall under low-, moderate-, and high-vulnerable zones, respectively. They also confirm the seaward-increasing tendency of vulnerability. The study demonstrates that optimizing a conventional DRASTIC model through Entropy weight modification and integrating the land use layer in the original DRASTIC (DRASTIC-EN-LU) model had the best performance. Among the intrinsic factors, D, I, and LU are the most sensitive parameters in the study area. The accurate assessment of groundwater vulnerability is necessary for control and prevention in the province of Ba Ria–Vung Tau. Findings of this study can help authorities of Ba Ria–Vung Tau province in groundwater protection and decision-making with regards to salinization.