Assessing the Impacts of Excessive Groundwater Extraction in the Vietnamese Mekong Delta and proposing Aquifer Recharge  Management Solutions

The Vietnamese Mekong Delta (VMD) is one of the largest economic centers in southern Vietnam, home to approximately 18 million inhabitants. The geological composition of the region encompasses seven aquifers namely Holocene (qh), Middle-Pleistocene (qp3, qp2-3, qp1), Pliocene (n22, n21) and Upper-Miocene (n13) characterized by porous formations and fractures, facilitating the percolation and retention of groundwater. In the region, groundwater is a vital role as a fundamental water resource, serving essential functions in domestic, agricultural, and industrial domains. However, the intensive extraction of groundwater leads to several negative impacts, including reduction of groundwater level, saline water intrusion into the groundwater, and the potential threat of land subsidence in several locations. This study aims to quantitatively assess the future change in groundwater level in VMD through the utilization of a FEFLOW forecasting model consideing several climate change groundwater exploitation scenarios. The results reveals a substantial decline in groundwater levels by the year 2100, ranging from 15 m to 25 m in the aquifers qp2-3, qp3, n22, n21, n13 and a deeper more than 35 m in the aquifer qp1. Due to the influence of the groundwater extraction process in the main aquifer, the groundwater level will be lowered, forming lower funnel-shaped depressions and a subsequent shift of saline boundary in the aquifer system.  The findings also underscore the occurrence of varying degrees of saline intrusion across all six aquifers, observed in both the Pleistocene (qp) and Neogene (n) aquifers. To mitigate the risks associated with saltwater intrusion, it is recommended to strategically plan the placement of water extraction wells at a considerable distance from the saline boundary. Additionally, it is advisable to implement measures focused on artificial replenishment, the development of water sources, and the promotion of surface water utilization, especially in regions experiencing water scarcity.