On the representation of subsea aquitards in models of offshore fresh groundwater

Solórzano-Rivas, S. Cristina; Werner, Adrian D.

doi:10.1016/j.advwatres.2017.11.025

Cited by 14 publications

(12 citation statements)

References 29 publications

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“…Extensive, low-permeability aquitards have trapped freshwater emplaced during periods of sea level lowstands in inner and middle shelf regions (Bratton, 2007 Gustafson et al, 2019;Hanebuth et al, 2002;Jiao et al, 2015;Kwong & Jiao, 2016;Marksammer et al, 2007;Reijenstein et al, 2011;Thomas et al, 2019;Uchupi et al, 2001;Zamrsky et al, 2020). Analytical and modeling studies provide further support that such a sedimentary architecture is conducive to OFG preservation (Knight et al, 2018;Kooi & Groen, 2001;Langevin et al, 2008;Michael et al, 2016;Morgan et al, 2018;Solorzano-Rivas & Werner, 2018;Thomas et al, 2019;Van Engelen et al, 2018). The base of most OFG bodies coincides with a change from coarse-to fine-grained sediments (predominantly sand to clay) (Micallef, 2020).…”

Section: Controlling Factors 231 Geological Factorsmentioning

confidence: 98%

Offshore Freshened Groundwater in Continental Margins

Micallef

Person

Berndt

et al. 2021

Reviews of Geophysics

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First reported in the 1960s, offshore freshened groundwater (OFG) has now been documented in most continental margins around the world. In this review we compile a database documenting OFG occurrences and analyze it to establish the general characteristics and controlling factors. We also assess methods used to map and characterize OFG, identify major knowledge gaps, and propose strategies to address them. OFG has a global volume of 1 × 10 6 km 3 ; it predominantly occurs within 55 km of the coast and down to a water depth of 100 m. OFG is mainly hosted within siliciclastic aquifers on passive margins and recharged by meteoric water during Pleistocene sea level lowstands. Key factors influencing OFG distribution are topography-driven flow, salinization via haline convection, permeability contrasts, and the continuity/connectivity of permeable and confining strata. Geochemical and stable isotope measurements of pore waters from boreholes have provided insights into OFG emplacement mechanisms, while recent advances in seismic reflection profiling, electromagnetic surveying, and numerical models have improved our understanding of OFG geometry and controls. Key knowledge gaps, such as the extent and function of OFG, and the timing of their emplacement, can be addressed by the application of isotopic age tracers, joint inversion of electromagnetic and seismic reflection data, and development of three-dimensional hydrological models. We show that such advances, combined with site-specific modeling, are necessary to assess the potential use of OFG as an unconventional source of water and its role in sub-seafloor geomicrobiology. Plain Language Summary This review paper considers offshore freshened groundwater (OFG), which is water hosted in sediments and rocks below the seafloor, with a total dissolved solid concentration lower than seawater. We have compiled >300 records to demonstrate that freshened groundwater occurs offshore on most continents around the world and has a global volume of 1 × 10 6 km 3. The majority of OFG was deposited when sea level was lower than today and is hosted in sandy sub-seafloor layers that are located within 55 km of coasts in water depths less than 100 m. We present a range of geochemical, geophysical, and modeling approaches that have successfully been used to investigate OFG systems. We also propose approaches to address key scientific questions related to OFG, including whether it may be used as an unconventional source of potable water in coastal areas.

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Section: Controlling Factors 231 Geological Factorsmentioning

confidence: 98%

Offshore Freshened Groundwater in Continental Margins

Micallef

Person

Berndt

et al. 2021

Reviews of Geophysics

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“…The Werner and Robinson (2018) solution is used here to provide exact distributions of the offshore freshwater-seawater interface under steady-state sharp-interface conditions. The conceptual model used by Werner and Robinson (2018) and others (e.g., Bakker, 2006; Solórzano-Rivas and Werner, 2018) for the offshore continuation of continental fresh groundwater is illustrated in Figure 1. This two-dimensional, cross-sectional conceptual model is based on the assumption of one-dimensional flow (i.e., the Dupuit approximation) within an offshore aquifer that is homogeneous and isotropic.…”

Section: Analytical Solutionmentioning

confidence: 99%

Dispersion effects on the freshwater–seawater interface in subsea aquifers

Solórzano-Rivas

Werner

Irvine

2019

Advances in Water Resources

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This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Highlights Dispersion effects on offshore freshwater extent and discharge investigated  Toe moves seaward monotonically with increased dispersion  Tip-dispersion relationship is non-monotonic  Dispersion increases fresh groundwater discharge to the sea

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“…This assumption is reasonable when the considered offshore submarine aquifer is far enough from the coastline. There are even many offshore freshwater submarine aquifers extending in all horizontal directions extensively and very far from the coastline [22][23][24][25][26]. In addition, several existing analytical studies assume that the coastal aquifer systems extend seaward infinitely (e.g., [10,14,17,27]).…”

Section: Mathematical Model and Analytical Solutionmentioning

confidence: 99%

“…Although there are some analytical solutions of tide-induced groundwater fluctuations in the submarine confined aquifer system in the offshore part (e.g., [14,17,18]), the dependency of the tide-induced groundwater head fluctuation in the offshore submarine aquifer on the model parameter was not analyzed or discussed. The offshore submarine aquifers are important both in water resources and in marine environments (e.g., [21][22][23][24][25][26]). Therefore, the study of the groundwater flow in offshore submarine aquifer systems is necessary and important.…”

Section: Introductionmentioning

confidence: 99%

Analytical Solution of Tidal Loading Effect in a Submarine Leaky Confined Aquifer System

Song¹,

et al. 2019

Geofluids

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Although there are many existing analytical studies of tidal groundwater level fluctuations in coastal aquifer systems, few of them focus on an offshore submarine aquifer. Here, we consider tidal groundwater head fluctuations in a submarine leaky confined aquifer overlain by a semipermeable seabed. Both the seabed and the confined aquifer are assumed to extend horizontally infinitely. A one-dimensional mathematical model is established to describe the problem, and the analytical solution is derived. The impacts of the tidal loading efficiency, hydraulic conductivity and elastic storage of the semipermeable layer and aquifer on the groundwater head fluctuations in the aquifer system are analyzed and discussed. Solution analyses indicated that tidal loading effects tend to enhance the amplitude of the tidal groundwater fluctuation in the confined aquifer system and to reduce the phase shift between the groundwater head and the sea tide fluctuations.

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On the representation of subsea aquitards in models of offshore fresh groundwater

Cited by 14 publications

References 29 publications

Offshore Freshened Groundwater in Continental Margins

Offshore Freshened Groundwater in Continental Margins

Dispersion effects on the freshwater–seawater interface in subsea aquifers

Analytical Solution of Tidal Loading Effect in a Submarine Leaky Confined Aquifer System

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