Laboratory and numerical investigation of saline intrusion in fractured coastal aquifers

Etsias, Georgios; Hamill, Gerard; Campbell, Daniel; Straney, Ryan; Benner, Eric M.; Águila, Jesús F.; McDonnell, Mark C.; Ahmed, Ashraf; Flynn, Raymond

doi:10.1016/j.advwatres.2021.103866

Cited by 22 publications

(21 citation statements)

References 79 publications

(70 reference statements)

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“…Moreover, multiple experimental studies demonstrated that the presence of extremely low permeability or impermeable formations, like walls (Abdoulhalik et al, 2017), or high permeability zones, like fractures (Etsias et al, 2021) can significantly alter groundwater hydrodynamics and lead to unique shapes of intruding saline wedges.…”

Section: Angle Of Intrusionmentioning

confidence: 99%

“…Chang et al, 2019;Guo et al, 2019;Kuan et al, 2019;Lee et al, 2019;Levanon et al, 2019;Memari et al, 2020;Na et al, 2019;Noorabadi et al, 2017;Shen et al, 2020;Stoeckl et al, 2019;Yu et al, 2019). Nevertheless, sandbox setups have been successfully employed to study freshwater-saltwater interface in aquifers with structuredsedimentary heterogeneity (Houben et al, 2018), in freshwater lenses, located in heterogeneous island aquifers (Dose et al, 2014;Stoeckl et al, 2015), as well as inside fractured porous media (Etsias et al, 2021). Regarding layered coastal aquifers in particular, the impact of stratified heterogeneity has been studied in correlation with a series of different phenomena.…”

Section: Introductionmentioning

confidence: 99%

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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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Section: Angle Of Intrusionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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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“…The final head difference applied was the same as the initial one (dh = 6 mm) to verify the occurrence of any hysteresis throughout the test. The experimental images recorded during the tests were analysed using automated image analysis techniques [15][16][17], and the toe length (TL) was derived. The saline water was allowed to penetrate into the aquifer by dropping the freshwater head to 135.7 mm, thereby imposing an initial head difference dh = 6 mm.…”

Section: Experimental Methodsmentioning

confidence: 99%

Towards a Correlation between Long-Term Seawater Intrusion Response and Water Level Fluctuations

Abdoulhalik

Ahmed

Abdelgawad

et al. 2021

Water

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Laboratory and numerical experiments were conducted to provide a quantitative steady-state analysis of the effect of incremental variations of water level on saltwater intrusion. The purpose was to seek mathematical correlations relating both the wedge toe length and the height along the coastline to the boundary head difference. The laboratory experiments were completed in a 2D sand tank where both freshwater and seawater levels were varied. The experiments were conducted for two bead sizes having different hydraulic conductivities. The numerical model SEAWAT was used to validate the results and then to perform sensitivity analysis. The experimental results show that at steady-state conditions, the logarithmic toe length could be expressed as a linear function of the boundary head difference. The linear relationship was recorded in both advancing and receding wedge phases. The linearity of the correlation was also well demonstrated with analytical solutions. Similar relationships were also derived in the scenarios where the sea level fluctuated while the freshwater boundary head was constant. The height of the saltwater wedge along the coastline was also found to be a linear function of the boundary head difference. The sensitivity analysis shows that the regression coefficients were sensitive to the hydraulic conductivity, the dispersivity, and the saltwater density, while the porosity and the rate of boundary head change induced negligible effects. The existence of a linear relationship between the logarithmic toe length and the boundary head difference was also well evidenced in a field-scale aquifer model for all the different hydrogeological aquifer conditions tested. This study is the first attempt in identifying the underlying correlation between the boundary water level variations and the main seawater intrusion (SWI) external metrics under controlled laboratory conditions, which is of great relevance from a water resources management perspective.

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“…The other major group of publications focusses on the numerical description of processes and effects of idealised or generalised heterogeneity, including fractures, connected to SWI or submarine groundwater discharge (e.g. Kerrou and Renard 2010;Sebben et al 2015;Etsias et al 2021). In general, literature related to hydrogeological aspects of fractures is abundant (Berkowitz 2002); hence, the following paragraphs will focus on properties in the topmost approximately 300 m of coastal areas, representing the typical depth of groundwater wells, and processes directly related to SWI in fractured crystalline bedrock.…”

Section: Characteristics Of Fractured (Crystalline) Bedrockmentioning

confidence: 99%

Review: Saltwater intrusion in fractured crystalline bedrock

Giese

Barthel

2021

Hydrogeol J

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During the past few years, the number of regional and national assessments of groundwater quality in regard to saltwater intrusion in coastal aquifers has increased steadily. However, most of the international literature on saltwater intrusion is focused on coastal plains with aquifers in unconsolidated material. Case studies, modelling approaches and parameter studies dealing with saltwater intrusion in those systems are abundant. While the hydrogeology of fractured rock has been intensively studied with both modelling approaches and parameter studies—mainly in relation to deep-laying fractured crystalline bedrock as potential waste repositories—case studies on saltwater intrusion in shallow fractured rocks are still an exception. This review summarizes the actual knowledge on saltwater intrusion in fractured crystalline rock. In combination with short overviews of the processes of saltwater intrusion, flow in fractured systems and the genesis of these systems, the review highlights the importance of the fracture systems and its specific characteristics. Fracture properties are a direct consequence of the geological history as well as the current situation of the coastal area. A holistic assessment of water quality in coastal areas hosting fractured crystalline bedrock therefore requires the combination of different approaches in order to investigate the impact of saltwater intrusion through the fractured system.

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Laboratory and numerical investigation of saline intrusion in fractured coastal aquifers

Cited by 22 publications

References 79 publications

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

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

Towards a Correlation between Long-Term Seawater Intrusion Response and Water Level Fluctuations

Review: Saltwater intrusion in fractured crystalline bedrock

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