Salinity distribution in the subterranean estuary of a meso-tidal high-energy beach characterized by Electrical Resistivity Tomography and direct push technology

Grünenbaum, Nele; Günther, Thomas; Greskowiak, Janek; Vienken, Thomas; Müller‐Petke, Mike; Massmann, Gudrun

doi:10.1016/j.jhydrol.2023.129074

Cited by 10 publications

(13 citation statements)

References 52 publications

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“…However, the pronounced loss of the freshwater lens along the MS transects on South Beach (and potentially concomitant vertical lens thinning) suggest that erosion has been the major SWI driver along the MS transect. In agreement with past studies, we demonstrate that short‐term groundwater monitoring programs only present a snapshot of coastal groundwater dynamics and are not representative of long‐term continuous changes in subsurface salinity distributions (Grünenbaum et al., 2023; Heiss & Michael, 2014; Paldor, Frederiks, & Michael, 2022). Coastal aquifers are challenging to monitor directly, and long‐term monitoring is prohibitively expensive, forcing coastal water resource management to rely heavily on numerical models calibrated to few field observations (Werner et al., 2017).…”

Section: Resultssupporting

confidence: 90%

Morphologic, Atmospheric, and Oceanic Drivers Cause Multi‐Temporal Saltwater Intrusion on a Remote, Sand Island

Cantelon,

Robinson,

Kurylyk

2023

Water Resources Research

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Small‐island populations disproportionately rely on fresh groundwater resources, which are increasingly threatened by salinization from changing ocean and climate conditions. This study investigates island groundwater dynamics and salinization over multiple timescales in response to marine, atmospheric, and morphologic drivers. To address this, new geophysical and hydrological datasets were collected on a remote sand island in the Northwest Atlantic Ocean between 2020‐2022 and compared to historical baseline data from the 1970s.Data reveal saltwater intrusion due to multi‐decadal erosion, seasonal climate patterns, tidal forcing, and episodic flooding from Atlantic hurricanes. Long‐term dune erosion has caused the freshwater lens to thin and become asymmetrical; however, a lagged groundwater response causes the freshwater lens to be in disequilibrium with present island morphology. The maximum vertical lens thickness is seasonally constant, but the lateral transition zone along the coast thickens and moves seaward in spring when the water table is high from precipitation and frequent beach flooding. Groundwater level and electrical conductivity along low‐lying beaches significantly increase following Atlantic hurricanes due to seawater flooding, and reach a maximum of 1.93 m above sea level and 38 mS/cm, respectively. While groundwater levels recover quickly, conductivity (salinity) remains elevated due to the short intervals between winter flood events that outpace freshening from meteoric recharge. Results emphasize the importance of multi‐temporal groundwater dynamics and feedbacks between coastal flooding, erosion, and salinization. Field‐based studies considering multiple drivers and timescales of saltwater intrusion are critical for understanding and managing coastal freshwater resources in an age of rapid environmental change.

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Section: Resultssupporting

confidence: 90%

Morphologic, Atmospheric, and Oceanic Drivers Cause Multi‐Temporal Saltwater Intrusion on a Remote, Sand Island

Cantelon,

Robinson,

Kurylyk

2023

Water Resources Research

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“…For instance, Röper et al (2014), Shen et al (2015), Zhang et al (2017) or Delwar et al (2024) mimicked coastal aquifers in laboratory experiments and found the freshwater–seawater interface in the STE to be far less stable than previously thought. These findings are of great value to further interpret the complexity of groundwater flow and transport in tidal real‐world STEs which were studied by, for example, Grünenbaum et al, 2023 or Waska et al, 2019.…”

Section: Introductionmentioning

confidence: 73%

“…We could show that iron oxides precipitated all along the position-stable interfaces as expected. However, previous numerical and/or experimental studies (e.g., Abarca et al, 2013;Greskowiak, 2014;Greskowiak & Massmann, 2021;Grünenbaum et al, 2023;Heiss & Michael, 2014;Robinson et al, 2007Robinson et al, , 2014Zhang et al, 2017) indicated that groundwater flow and transport can be quiet dynamic under more realistic conditions leading to transient redox interfaces (Greskowiak et al, 2023), and with that, presumably a widening of the iron curtain formation zone.…”

Section: Burke Et Al [2013]mentioning

confidence: 99%

“…For instance, Röper et al (2014), Shen et al (2015), Zhang et al (2017) or Delwar et al (2024) mimicked coastal aquifers in laboratory experiments and found the freshwater-seawater interface in the STE to be far less stable than previously thought. These findings are of great value to further interpret the complexity of groundwater flow and transport in tidal realworld STEs which were studied by, for example, Grünenbaum et al, 2023or Waska et al, 2019 In this study, we mimic the 'iron curtain' formation below a beach in a sand tank experiment to highlight the importance of the USP as well as the associated mixing zone at the interface between USP and underlying freshwater on mixing controlled reactions in tidal STEs.…”

Section: Introductionmentioning

confidence: 99%

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Visualizing the ‘iron curtain’ formation in the subterranean estuary using sand tank experiments

Grünenbaum,

Volk,

Delwar

et al. 2024

Hydrological Processes

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“…The presence and morphology of USPs are strongly dependent on factors including beach morphology, tidal range, density differences, and heterogeneity (Bakhtyar et al., 2013; Evans & Wilson, 2016; Robinson et al., 2018). The USP dimensions and spatial and temporal stability are also dependent on the magnitude and timing of external forcing (Buquet et al., 2016; Fang et al., 2021; Fang, Zheng, Guo, et al., 2022; Fang, Zheng, Wang et al., 2022; Grünenbaum et al., 2023; Kuan et al., 2012; Yu et al., 2019). Despite the relationship between tidal amplitude and USP morphology and dynamics, numerical modeling studies investigating USP dynamics, or more generally aquifer‐ocean interactions, have been limited to micro‐ (and occasionally macro‐) tidal ranges (e.g., Levanon et al., 2017; Yang et al., 2013).…”

Section: Introductionmentioning

confidence: 99%

Mega‐Tidal and Surface Flooding Controls on Coastal Groundwater and Saltwater Intrusion Within Agricultural Dikelands

LeRoux,

Frey,

Lapen

et al. 2023

Water Resources Research

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Climate change will increase sea levels, driving saltwater into coastal aquifers and impacting coastal communities and land use viability. Coastal aquifers are also impacted by tides that control groundwater‐ocean interactions and maintain an “upper saline plume” (USP) of brackish groundwater. Coastal dikes are designed to limit the surface impacts of high‐amplitude tides, but, due to ongoing sea‐level rise (SLR), low‐lying dikelands and underlying aquifers are becoming increasingly vulnerable to flooding from high tides and storm surges. This study combines field observations with numerical modeling to investigate ocean‐aquifer mixing and future saltwater intrusion dynamics in a mega‐tidal (tidal range >8 m) dikeland along the Bay of Fundy in Atlantic Canada. Field data revealed strong connectivity between the ocean and coastal aquifer, as evidenced by pronounced tidal oscillations in deeper groundwater heads and an order of magnitude intra‐tidal change in subsurface electrical resistivity. Numerical model results indicate that SLR and surges will force the migration of the USP landward, amplifying salinization of freshwater resources. Simulated storm surges can overtop the dike, contaminating agricultural soils. The presence of dikes decreased salinization under low surge scenarios, but increased salinization under larger overtopping scenarios due to landward ponding of seawater behind the dike. Mega‐tidal conditions maintain a large USP and impact aquifer freshening rates. Results highlight the vulnerability of terrestrial soil landscapes and freshwater resources to climate change and suggest that the subsurface impacts of dike management decisions should be considered in addition to protection measures associated with surface saltwater intrusion processes.

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Salinity distribution in the subterranean estuary of a meso-tidal high-energy beach characterized by Electrical Resistivity Tomography and direct push technology

Cited by 10 publications

References 52 publications

Morphologic, Atmospheric, and Oceanic Drivers Cause Multi‐Temporal Saltwater Intrusion on a Remote, Sand Island

Morphologic, Atmospheric, and Oceanic Drivers Cause Multi‐Temporal Saltwater Intrusion on a Remote, Sand Island

Visualizing the ‘iron curtain’ formation in the subterranean estuary using sand tank experiments

Mega‐Tidal and Surface Flooding Controls on Coastal Groundwater and Saltwater Intrusion Within Agricultural Dikelands

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