Assessing the potential of the multi-aquifer subsurface of the Mekong Delta (Vietnam) for land subsidence due to groundwater extraction

Land subsidence rates of similar to 1-4 cm yr(-1) are measured in the low-lying Vietnamese Mekong Delta. These relatively high subsidence rates are attributed to groundwater extraction, which has increased drastically over the past decades due to growing domestic, agricultural and industrial demands. As a result, hydraulic heads in aquifers are dropping, on average 0.3-0.7 m yr(-1). There is an urgent need to go from measurements to predictions in order to test possible future groundwater management scenarios and to reduce the increase of flood risk, salt water intrusion and, on the longer term, prevent the delta from drowning. In this study, we aim to assess the subsidence potential of the multi-aquifer subsurface of the Mekong delta due to groundwater extraction. The first step is to gain a thorough understanding of the complex sedimentary architecture of the heterogeneous subsurface. Combined with the related geotechnical properties, the subsurface build-up determines the subsidence potential. Here, we present our approach to develop a 3-D geo-hydrological model based on lithological borehole data, geophysical sedimentary properties, palaeogeography and conceptual models of delta evolution.