Seawater intrusion in fractured coastal aquifers influenced by tides: Laboratory and numerical investigations

Xie, Yifan; Wang, Yi; Zhang, Jiaxu; Ye, Yu; Shen, Chengji; Zeng, Yi; Wu, Jichun; Luo, Jian; Lu, Chunhui

doi:10.1016/j.jhydrol.2023.129637

Cited by 3 publications

(5 citation statements)

References 42 publications

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“…From the experimental results in Xie et al (2023) and numerical simulation results (Figure 2), the simulated results matched the experimental in all cases well (Figure 2). We can find that tidal forcing formed a USP and SW in the intertidal zone where saltwater infiltrated near the high tide mark and was discharged near the low tide mark.…”

Section: Model Calibrationsupporting

confidence: 59%

“…To verify the reliability of the model, we developed a numerical model consistent with the lab experiment of Xie et al (2023), with an aquifer length of 4 m and width of 0.7 m and porosity of 0.45; the parameters a and n i were set to 5.9 m -1 and 2.68, respectively, and the longitudinal dispersion coefficient (a L ) was 0.005 m and transverse dispersion coefficient (a T ) was 0.0005 m [for the specific parameters, please refer to Xie et al (2023) for details]. We consider three case conditions: non-preferential flow, preferential flow at x = 0.8 m, z = 0.3 m, and preferential flow at x = 1.8 m, z = 0.3 m, and the preferential flow scales and parameter settings are also consistent with those of Xie et al (2023).…”

Section: Model Calibrationmentioning

confidence: 99%

“…The high hydraulic conductivity of the preferential flow increased the salt transport, resulting in a larger USP than the nonpreferential flow; this could control SWI to some extent. Several previous studies have been performed to investigate saltwaterfreshwater mixing dynamics-for example, Xie et al (2023) investigated the effect of fracture characteristics on salinity distribution and groundwater flow through experiments and numerical simulations. They reported that the vertical fractures had a limited impact on most SWI properties.…”

Section: Starting Position (M)mentioning

confidence: 99%

“…FIGURE 2Experimental (A1), (B1), (C1)(Xie et al, 2023) and simulated (A2), (B2), (C2) results of non-preferential flow and preferential flow. The horizontal dotted lines is tidal range; in (A1), (B1), and (C1), the solid black lines indicate the numerical results for 50% salinity contour isohalines byXie et al (2023), and in (A2), (B2), and (C2), the solid black lines indicate 50% salinity contour isohalines based on COMSOL. PF is preferential flow.…”

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confidence: 99%

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Nitrate fate in coastal unconfined aquifers influenced by preferential flows

Gao,

Kong,

Wang

et al. 2024

Front. Mar. Sci.

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This study examined the influence of preferential flow on pore water flows and marine nitrogen transport reaction in variable saturation and variable density coastal aquifers. The 2-D unconfined aquifer model established was based on the software COMSOL by coupling the dynamic and chemical processes together. The results showed that preferential flow affects groundwater flow and salinity distribution, leading to a more complicated mixing process. The preferential flow resulted in an increase in mixing zone area and the upper saline plume area of 10.33 and 2.62 m2, respectively, a decrease in saltwater wedge area of 7.22 m2, and an increase in nitrate (NO3-) removal efficiency from 7.9% to 8.97%. The NO3- removal efficiency increases progressively with the depth (h) and quantity (n) of preferential flows; however, it decreases after a certain quantity. Further quantitative analysis revealed an increase in the intensity of nitrification and dissolved oxygen inflow flux with preferential flow depth and quantity increase. This phenomenon usually occurs on coasts where biological caves are abundant. The results also offer significant implications for designing engineering measures to mitigate saltwater intrusion and are significant to prevent groundwater quality deterioration in coastal zones.

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Section: Model Calibrationsupporting

confidence: 59%

Section: Model Calibrationmentioning

confidence: 99%

Section: Starting Position (M)mentioning

confidence: 99%

mentioning

confidence: 99%

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Nitrate fate in coastal unconfined aquifers influenced by preferential flows

Gao,

Kong,

Wang

et al. 2024

Front. Mar. Sci.

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“…Coastal aquifers play a vital role as a pathway for land-sourced solutes to enter the sea, and the hydrodynamic processes within the aquifer significantly influence the migration characteristics of these solutes, thereby impacting the water ecology and environment of the nearshore sea (Morales-Ojeda et al, 2010). Numerous studies conducted in the past decades have primarily focused on the hydrodynamics in coastal aquifers, considering the individual or combined effects of tides (Robinson et al, 2007;Xie et al, 2023), waves (Xin et al, 2010;, sea level rise (Werner and Simmons, 2009;Guimond et al, 2022;Chambers et al, 2023), aquifer heterogeneity (Song et al, 2022;Zhuang et al, 2023), and rainfall (Geng and Boufadel, 2017;Yu et al, 2017;Pandey et al, 2023).…”

Section: Introductionmentioning

confidence: 99%

Variable-density solute transport in unconfined coastal aquifers with a subsurface dam

Fan,

Shen,

Xie

et al. 2024

Front. Mar. Sci.

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Recently, the influence of subsurface dams on solute transport in coastal aquifers has become a hot research topic. Although many studies have been conducted, the combined effects of subsurface dam and tides on variable-density solute transport remain unclear, and this study aimed to fill this research gap. In the current study, a numerical model representing a 2-D cross-shore coastal aquifer was established. The model simulated cases with and without a subsurface dam, and sensitivity analysis cases with different height and location of the subsurface dam and solute concentration. The results show that a subsurface dam blocks a portion of the solute plume, which can only be discharged by dilution at the edges, thereby altering its discharge pattern and reducing their discharge rate. The addition of a subsurface dam may either prolong or shorten the residence time of solute,depending on the location rather than the height of the subsurface dam. In particular, a more landward subsurface dam would significantly increase the residence time; sensitivity analysis demonstrates that both the landward shift and the height increase of the subsurface dam contribute to a heightened ratio of dynamic mass distribution for the solute plume within the freshwater and saltwater zones of the aquifer, with maximum changes in mass distribution ratios of 87.22% and 300%, respectively. Also, these factors cause the solute to migrate both seaward and landward, respectively, across the primary outflow regions of the aquifer-ocean interface. Results from this study may provide theoretical guidance for the optimal design and environmental impact assessment of subsurface dams.

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Research methods for seawater intrusion in China and recommendations for novel radium-radon technologies

Zhang,

2024

Marine Environmental Research

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Seawater intrusion in fractured coastal aquifers influenced by tides: Laboratory and numerical investigations

Cited by 3 publications

References 42 publications

Nitrate fate in coastal unconfined aquifers influenced by preferential flows

Nitrate fate in coastal unconfined aquifers influenced by preferential flows

Variable-density solute transport in unconfined coastal aquifers with a subsurface dam

Research methods for seawater intrusion in China and recommendations for novel radium-radon technologies

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