Vulnerability Assessment of the Upper-Middle Pleistocene (qp_2-3) Aquifer in Ho Chi Minh City, Vietnam Using GIS and Expanded DRASTIC Methods

Abstract

The groundwater vulnerability assessment model (DRASTIC) for zoning sensitivity based on natural and objective factors of aquifers is currently used and applied widely. In this study, we have expanded the weights in the DRASTIC index through the Entropy weight-based technique and visualized them in association with GIS for assessing the vulnerability of the Upper-Middle Pleistocene aquifer in Ho Chi Minh City, Vietnam. The value of Entropy weights calculated from the collected dataset of 106 monitoring boreholes of the study area. The Entropy-DRASTIC results divided into three categories: 9.45% of the study area was in the high vulnerability zones, low and medium vulnerability zones are 21.5% and 69.05% of the total study area, respectively. The highly vulnerable area, which is shallow aquifer roofs and recharged significantly (directly from rains or runoff from the surface flows exposed to contaminants from runoff flows). Low vulnerability areas with clay cover are weak permeability and medium vulnerability area is a sizable transitional zone surrounding the high and low vulnerability. This result suggests that the DRASTIC index model in association with GIS is a useful tool to assist policymakers in formulating solutions for the use of groundwater resources. Importantly, this finding is useful to the local authorities in shaping regulations on the use and exploitation of groundwater resources in suburban areas, where the public water supply network is inadequate, constrained groundwater resource and exposed to contamination.