Vertical leakage in sharp-interface seawater intrusion models of layered coastal aquifers

Mehdizadeh, S. Sadjad; Werner, Adrian D.; Vafaie, Freydoon; Badaruddin, Sugiarto

doi:10.1016/j.jhydrol.2014.08.027

Cited by 33 publications

(25 citation statements)

References 33 publications

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“…To overcome this limitation, we considered heterogeneities corresponding to vertical stratification. This picture is widespread and agrees with several coastal sedimentary aquifers [61,77]. We assume that heterogeneity is perfectly layering with an exponential trend of hydraulic conductivity with depth.…”

Section: The Semi-analytical Solutionsupporting

confidence: 84%

“…The effect of anisotropy on SWI has been often investigated using the sharp interface model [77], which assumes that freshwater and saltwater are immiscible [78][79][80][81]. Abarca et al [13] were the first to investigate the influence of anisotropy on the saltwater wedge using the DDF model.…”

Section: Effect Of Anisotropy On Swi In a Homogenous Aquifermentioning

confidence: 99%

“…Significant research has been devoted to the evaluation of the influence of heterogeneity on SWI [9,10,60,72]. Particular attention has been paid to the stratified heterogeneity using the sharp interface model [77,[82][83][84]. The influence of stratification on SWI has been also investigated experimentally and numerically (using the DDF model) [61,77,85].…”

Section: Coupled Effect Of Anisotropy and Stratified Heterogeneity Onmentioning

confidence: 99%

See 2 more Smart Citations

A Generalized Semi-Analytical Solution for the Dispersive Henry Problem: Effect of Stratification and Anisotropy on Seawater Intrusion

Fahs

Koohbor

Belfort

et al. 2018

Water

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The Henry problem (HP) continues to play a useful role in theoretical and practical studies related to seawater intrusion (SWI) into coastal aquifers. The popularity of this problem is attributed to its simplicity and precision to the existence of semi-analytical (SA) solutions. The first SA solution has been developed for a high uniform diffusion coefficient. Several further studies have contributed more realistic solutions with lower diffusion coefficients or velocity-dependent dispersion. All the existing SA solutions are limited to homogenous and isotropic domains. This work attempts to improve the realism of the SA solution of the dispersive HP by extending it to heterogeneous and anisotropic coastal aquifers. The solution is obtained using the Fourier series method. A special hydraulic conductivity-depth model describing stratified heterogeneity is used for mathematical convenience. An efficient technique is developed to solve the flow and transport equations in the spectral space. With this technique, we show that the HP can be solved in the spectral space with the salt concentration as primary unknown. Several examples are generated, and the SA solutions are compared against an in-house finite element code. The results provide high-quality data assessed by quantitative indicators that can be effectively used for code verification in realistic configurations of heterogeneity and anisotropy. The SA solution is used to explain contradictory results stated in the previous works about the effect of anisotropy on the saltwater wedge. It is also used to investigate the combined influence of stratification and anisotropy on relevant metrics characterizing SWI. At a constant gravity number, anisotropy leads to landward migration of the saltwater wedge, more intense saltwater flux, a wider mixing zone and shallower groundwater discharge zone to the sea. The influence of stratified heterogeneity is more pronounced in highly anisotropic aquifers. The stratification rate and anisotropy have complementary effects on all SWI metrics, except for the depth of the discharge zone.

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Section: The Semi-analytical Solutionsupporting

confidence: 84%

Section: Effect Of Anisotropy On Swi In a Homogenous Aquifermentioning

confidence: 99%

Section: Coupled Effect Of Anisotropy and Stratified Heterogeneity Onmentioning

confidence: 99%

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A Generalized Semi-Analytical Solution for the Dispersive Henry Problem: Effect of Stratification and Anisotropy on Seawater Intrusion

Fahs

Koohbor

Belfort

et al. 2018

Water

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“…Following Mehdizadeh et al . [], x tip and x toe are calculated using 5% of seawater salinity. By connecting the toe and the tip of the interface with a straight line, the interface alignment ( θ ) is defined as shown in Figures a and b.…”

Section: Wts Conceptual Models: Active and Passive Swimentioning

confidence: 98%

“…The seawater wedge ''toe'' is the extent of seawater along the aquifer basement (x toe [L]; Figure 1). Following Mehdizadeh et al [2014], x tip and x toe are calculated using 5% of seawater salinity. By connecting the toe and the tip of the interface with a straight line, the interface alignment (h) is defined as shown in Figures 1a and 1b.…”

Section: Wts Conceptual Models: Active and Passive Swimentioning

confidence: 99%

Water table salinization due to seawater intrusion

Badaruddin

Werner

Morgan

2015

Water Resources Research

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Seawater intrusion (SWI) is a significant threat to freshwater resources in coastal aquifers around the world. Previous studies have focused on SWI impacts involving salinization of the lower domain of coastal aquifers. However, under certain conditions, SWI may cause salinization of the entire saturated zone of the aquifer, leading to water table salinization (WTS) in unconfined aquifers by replacing freshwater within the upper region of the saturated zone with seawater, thereby posing a salinity threat to the overlying soil zone. There is presently limited guidance on the extent to which WTS may occur as a secondary impact of SWI. In this study, physical experiments and numerical modeling were used to explore WTS associated with SWI in various nontidal, unconfined coastal aquifer settings. Laboratory experiments and corresponding numerical simulations show that significant WTS can occur under active SWI (i.e., the freshwater hydraulic gradient slopes toward the land) because the cessation of freshwater discharge to the sea and the subsequent landward flow across the entire sea boundary eventually lead to water table salinities approaching seawater concentration. WTS during active SWI is larger under conditions of high hydraulic conductivity, rapid SWI, high dispersivity and for deeper aquifers. Numerical modeling of four published field cases demonstrates that rates of WTS of up to 60 m/yr are plausible. Under passive SWI (i.e., the hydraulic gradient slopes toward the sea), minor WTS may arise as a result of dispersive processes under certain conditions (i.e., high dispersivity and hydraulic conductivity, and low freshwater discharge). Our results show that WTS is probably widespread in coastal aquifers experiencing considerable groundwater decline sustained over several years, although further evidence is needed to identify WTS under field settings.

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The impact of aquifer stratification on saltwater intrusion characteristics. Comprehensive laboratory and numerical study

Etsias

Hamill

Águila

et al. 2021

Hydrological Processes

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Laboratory experiments and numerical simulations were utilized in this study to assess the impact of aquifer stratification on saltwater intrusion. Three homogeneous and six layered aquifers were investigated. Image processing algorithms facilitated the precise calculation of saltwater wedge toe length, width of the mixing zone, and angle of intrusion. It was concluded that the length of intrusion in stratified aquifers is predominantly a function of permeability contrast, total aquifer transmissivity and the number of heterogeneous layers, being positively correlated to all three. When a lower permeability layer overlays or underlays more permeable zones its mixing zone widens, while it becomes thinner for the higher permeability strata. The change in the width of the mixing zone (WMZ) is positively correlated to permeability contrast, while it applies to all strata irrespectively of their relative vertical position in the aquifer. Variations in the applied hydraulic head causes the transient widening of WMZ.These peak WMZ values are larger during saltwater retreat and are negatively correlated to the layer's permeability and distance from the aquifer's bottom. Moreover, steeper angles of intrusion are observed in cases where low permeability layers overlay more permeable strata, and milder ones in the inverse aquifer setups. The presence of a low permeability upper layer results in the confinement of the saltwater wedge in the lower part of the stratified aquifer. This occurs until a critical hydraulic head difference is applied to the system. This hydraulic gradient value was found to be a function of layer width and permeability contrast alike.

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Vertical leakage in sharp-interface seawater intrusion models of layered coastal aquifers

Cited by 33 publications

References 33 publications

A Generalized Semi-Analytical Solution for the Dispersive Henry Problem: Effect of Stratification and Anisotropy on Seawater Intrusion

A Generalized Semi-Analytical Solution for the Dispersive Henry Problem: Effect of Stratification and Anisotropy on Seawater Intrusion

Water table salinization due to seawater intrusion

The impact of aquifer stratification on saltwater intrusion characteristics. Comprehensive laboratory and numerical study

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