Three-dimensional hydrostratigraphical modelling to support evaluation of recharge and saltwater intrusion in a coastal groundwater system in Vietnam

Abstract

Saltwater intrusion is generally related to seawater-level rise or induced intrusion due to excessive groundwater extraction in coastal aquifers. However, the hydrogeological heterogeneity of the subsurface plays an important role in (non-)intrusion as well. Local hydrogeological conditions for recharge and saltwater intrusion are studied in a coastal groundwater system in Vietnam where geological formations exhibit highly heterogeneous lithologies. A three-dimensional (3D) hydrostratigraphical solid model of the study area is constructed by way of a recursive classification procedure. The procedure includes a cluster analysis which uses as parameters geological formation, lithological composition, distribution depth and thickness of each lithologically distinctive drilling interval of 47 boreholes, to distinguish and map well-log intervals of similar lithological properties in different geological formations. A 3D hydrostratigraphical fence diagram is then generated from the constructed solid model and is used as a tool to evaluate recharge paths and saltwater intrusion to the groundwater system. Groundwater level and chemistry, and geophysical direct current (DC) resistivity measurements, are used to support the hydrostratigraphical model.Results of this research contribute to the explanation of why the aquifer system of the study area is almost uninfluenced by saltwater intrusion, which is otherwise relatively common in coastal aquifers of Vietnam.

Influence of coastal groundwater salinization on the distribution and risks of heavy metals

“…Groundwater is also important drinking/ domestic water resource in many countries and regions (Béjar-Pizarro et al, 2017;Eschauzier et al, 2013;Fram and Belitz, 2011). Groundwater has attracted wide attention due to various problems caused by overextraction such as land subsidence (Zhu et al, 2015) and seawater/saltwater intrusion (Tam et al, 2014) as well as groundwater quality deterioration such as salinization (Du et al, 2015;Han et al, 2014) and pollution (Santucci et al, 2018;Wen et al, 2018;Wu et al, 2018a).…”

The effects of high salinity on nitrogen removal and the formation characteristics of aerobic granular sludge

“…The intrusion of seawater caused by excessive groundwater extraction and the rising sea level due to global warming add to the volume of high-salinity wastewater flowing into the sewage treatment plants in coastal areas [1][2][3]. Furthermore, the high-salinity wastewater generated by marine aquaculture and seafood processing industries is known to be a factor impacting the efficient treatment of the contamination sources in established wastewater treatment plants [4,5].…”

Summary of responses

“…These loading styles are examined with and without pumping. The results address important questions for the BAS which are likely also relevant to similarly extensive and strategically important fluvio-deltaic aquifer systems elsewhere in south Asia (Fendorf et al, 2010;Benner et al, 2008;Larsen et al, 2008;Tam et al, 2014;Xu et al, 2011): how can piezometer heads in the poroelastic aquifer be used to indicate recharge, as required for conventional groundwater resources management; under what conditions can piezometer heads be used to measure ΔTWS using geological weighing lysmetry; can ground surface deflections be related to changes in groundwater storage; and what errors may arise if the poroelastic behaviour of the aquifer is ignored? Second, we apply the partial coupling approach to these questions in the BAS, with reference to multi-level piezometer data from Khulna and Laksmipur in southern Bangladesh (Fig.…”