Assessment of the impact of sea-level rise on steady-state seawater intrusion in a layered coastal aquifer

Abstract

Previous studies on the impact of sea-level rise (SLR) on seawater intrusion (SWI) are mostly based on the assumption of a homogeneous coastal aquifer. In this study, we extend those studies by investigating SLR-induced SWI in a layered coastal aquifer using the analytical method developed by Strack and Ausk (2015). We provide analytical solutions for steady-state SWI in confined and unconfined coastal aquifers, where both constant-head and constant-flux inland boundary conditions are considered. The analysis based on a three-layer aquifer indicates that in general aquifer stratification affects either or both the initial location and response distance of the interface toe. Specifically, for flux-controlled unconfined coastal systems, the toe response distance driven by SLR is a linear function of the hydraulic conductivity of the top layer and independent of hydraulic conductivities of lower layers. Using an equivalent homogeneous hydraulic conductivity (derived based on the initial interface toe location before SLR) would result in overestimation or underestimation of the toe response distance, depending on the hydraulic conductivities and thicknesses of the layers. For flux-controlled confined layered coastal systems, by contrast, SLR can not cause variation of the steady-state interface toe location, which is consistent with previous findings for homogeneous coastal aquifers. The interface toe location in head-controlled layered coastal systems is only a function of relative hydraulic conductivities between the layers. Moreover, the effect of the layer thickness on the interface toe location and response distance in the head-controlled system exhibits a more complicated pattern than in the flux-controlled coastal system, as changing the layer thickness changes both the overall aquifer transmissivity and inland freshwater flux. The results obtained enhance the understanding of the impact of SLR on SWI, which could provide a first-order assessment tool for relevant practitioners.

A Study on the Cause of Layered Seawater Intrusion in the Daqing River Estuary of Liaodong Bay, China

“…A coastal stratum deposit is affected by the alluvial-diluvial effects of coastal rivers and presents the stratification phenomenon. Some scholars have studied the law of seawater intrusion in the multi-layered aquifer system [7,19,21,42,[53][54][55][56][57]. A few studies have considered seawater intrusion under the influence of pumping in multi-layered aquifers.…”

Experiment and Numerical Simulation of Seawater Intrusion under the Influences of Tidal Fluctuation and Groundwater Exploitation in Coastal Multilayered Aquifers

“…Two types of flow models were developed for seawater intrusion simulation, including the sharp interface models and mixing interface models [14,[19][20][21][22][23][24]. There are many analytical solutions for variable density flow models to solve the coupled seawater intrusion equations under special conditions [6,19,20,25]. Most of the analytical solutions are predominantly based on the Ghyben-Herzberg relation in the sharp interface models, in which the freshwater and saltwater are treated as separated fluids by an interface.…”

Numerical investigation on seawater intrusion and water leakage in different types of stratified coastal aquifers

“…Recently, studies have concentrated on different types of heterogeneity and their proper solutions [10,[20][21][22][23]. Shi et al [24] examined the effect of layered coastal aquifer on SWI by using the analytical method developed by Strack and Ausk (2015) [21]. Their results indicated that in general the initial location and response distance of the interface toe were affected by aquifer stratification [24].…”

“…Shi et al [24] examined the effect of layered coastal aquifer on SWI by using the analytical method developed by Strack and Ausk (2015) [21]. Their results indicated that in general the initial location and response distance of the interface toe were affected by aquifer stratification [24]. For stratified aquifers, Lu et al [25] conducted a series of experiments and numerical simulations to investigate the effect of parameters involved in SWI.…”