Extending Electromagnetic Methods to Map Coastal Pore Water Salinities

Greenwood, W. J.; Kruse, Sarah; Swarzenski, Peter W.

doi:10.1111/j.1745-6584.2005.00137.x

Cited by 19 publications

(17 citation statements)

References 14 publications

(19 reference statements)

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“…The processing resolution was optimized by using a starting model with the apparent resistivity pseudo‐section coupled to real bathymetry and conductivity/temperature data collected at electrode 28 and 56. The best‐fitting layered model was then developed using an iterative least squares smooth model inversion method [ Greenwood et al , 2006].…”

Section: Methodsmentioning

confidence: 99%

Combined time‐series resistivity and geochemical tracer techniques to examine submarine groundwater discharge at Dor Beach, Israel

Swarzenski

Burnett

Greenwood³

et al. 2006

Geophysical Research Letters

106

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[1] A high-resolution, stationary geophysical and geochemical survey was conducted at Dor Beach, Israel, to examine the shallow coastal hydrogeology and its control on the exchange of submarine groundwater with the shallow Mediterranean Sea. Time-series resistivity profiles using a new 56 electrode (112-m long) marine cable produced detailed profiles of the fresh water/salt water interface and the subtle response of this interface to tidal excursions and other forcing factors. Such information, when ground-truthed with representative pore water salinities and formation resistivity values, can provide unique information of the extent and rates of submarine groundwater discharge (SGD). Time-series 222 Rn measurements of the adjacent coastal water column complemented these geophysical techniques and were modeled to yield integrated advective flow rates across the sediment/water interface, which at Dor Beach ranged from about 0 to 30 cm day À1 (mean = 7.1 cm d À1 ), depending on the tidal range. Such results suggest that the underlying hydrogeologic framework at Dor is favorable for substantial SGD. Extrapolating these SGD estimates across a 100-m wide coastal zone implies that the Rn-derived SGD rate would equal $7.1 m 3 d À1 per m of shoreline, and that the source of this discharging groundwater is a complex mixture of fresh groundwater derived from the upland Kurkar deposits, as well as locally recycled seawater.

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Section: Methodsmentioning

confidence: 99%

Combined time‐series resistivity and geochemical tracer techniques to examine submarine groundwater discharge at Dor Beach, Israel

Swarzenski

Burnett

Greenwood³

et al. 2006

Geophysical Research Letters

106

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“…Processing resolution was optimized using a starting model with the apparent resistivity pseudo‐section coupled to the real bathymetry and conductivity/temperature data, collected at electrode 14. The best‐fitting layered model was then developed using an iterative least‐squares smooth model inversion method (Greenwood et al , 2006).…”

Section: Comparison Of Observation With Simulationmentioning

confidence: 99%

Submarine groundwater discharge and seawater circulation in a subterranean estuary beneath a tidal flat

Nakada

Yasumoto

Taniguchi

et al. 2011

Hydrological Processes

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Abstract:A numerical simulation and stationary geophysical survey at Omaehama, Japan, described the hydrogeology in a tidal flat and adjacent sea water column. The simulation of a tidally influenced aquifer with inland fresh groundwater discharges showed three circulations in the subterranean tidal flat estuary: a small, tide-induced recirculation (TIR) near the sloping beach, a deeper circulation (DC) across the interface between saltwater and freshwater, and a large, tidal flat-induced circulation (TFIC) in the offshore subterranean tidal flat and slope. The horizontal distribution of the simulated submarine groundwater discharge (SGD) showed two peaks, depending on the distance from the coast along the transect line of tidal flat; the offshore peak was quantitatively consistent with the previously observed peak based on automated seepage measurements. Time-series of the observed resistivity profiles using a marine cable (140 m) showed the structure of the fresh water/salt water interface, and indicated a salt wedge intruding from the bottom aquifer and infiltration at the surface in the beach and nearshore tidal flat. The qualitative structure of the resistivity hardly changed at each tidal stage. These results qualitatively validated the circulation patterns shown by the numerical simulation. The source of this discharging groundwater in the tidal flat is a complex mixture of fresh groundwater derived from the landward aquifer, as well as locally recycled seawater, which can contribute to the purification of the nearshore seawater.

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“…Although subterranean resistivity is influenced by variations in lithology and porosity, it is primarily controlled by interstitial salinity (Manheim et al, 2004;Greenwood et al, 2006). In the present study, resistivity was measured using stationary deployment of a 112 m long cable with 56 electrodes in a dipole-dipole array coupled to an Advanced Geosciences SuperSting R8 resistivity meter.…”

Section: Resistivity Measurementsmentioning

confidence: 99%

“…The resulting data were processed to resolve the best fit layered earth model using EarthImager 2D 2.0.8 software with an iterative least squares smooth model inversion method. Resolution of sharp salinity boundaries was increased by using a starting model where the apparent resistivity pseudo-section was overlain by measured water column resistivity and seabed bathymetry (Greenwood et al, 2006).…”

Section: Resistivity Measurementsmentioning

confidence: 99%

Submarine groundwater discharge to Tampa Bay: Nutrient fluxes and biogeochemistry of the coastal aquifer

Kroeger¹,

Swarzenski²,

Greenwood³

et al. 2007

Marine Chemistry

Self Cite

122

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To separately quantify the roles of fresh and saline submarine groundwater discharge (SGD), relative to that of rivers, in transporting nutrients to Tampa Bay, Florida, we used three approaches (Darcy's Law calculations, a watershed water budget, and a 222 Rn mass-balance) to estimate rate of SGD from the Pinellas peninsula. Groundwater samples were collected in 69 locations in the coastal aquifer to examine biogeochemical conditions, nutrient concentrations and stoichiometry, and salinity structure. Salinity structure was also examined using stationary electrical resistivity measurements. The coastal aquifer along the Pinellas peninsula was chemically reducing in all locations sampled, and that condition influences nitrogen (N) form and mobility of N and PO 4 3− . Concentrations of NH 4 + , PO 4 3− and ratio of dissolved inorganic N (DIN) to PO 4 3− were all related to measured oxidation/reduction potential (pε) of the groundwater. Ratio of DIN: PO 4 3− was below Redfield ratio in both fresh and saline groundwater. Nitrogen occurred almost exclusively in reduced forms, NH 4 + and dissolved organic nitrogen (DON), suggesting that anthropogenic N is exported from the watershed in those forms. In comparison to other SGD studies, rate of PO 4 3− flux in the seepage zone (μM min Tampa Bay was higher than previous estimates, likely due to 1) high watershed population density, 2) chemically reducing conditions, and 3) high ion concentrations in fresh groundwater. Estimates of freshwater groundwater flux indicate that the ratio of groundwater discharge to stream flow is ∼ 20 to 50%, and that the magnitudes of both the total dissolved nitrogen and PO 4 3− loads due to fresh SGD are ∼ 40 to 100% of loads carried by streams. Estimates of SGD based on radon inventories in near-shore waters were 2 to 5 times greater than the estimates of freshwater groundwater discharge, suggesting that brackish and saline SGD is also an important process in Tampa Bay and results in flux of regenerated N and P from sediment to surface water. Published by Elsevier B.V.

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Extending Electromagnetic Methods to Map Coastal Pore Water Salinities

Cited by 19 publications

References 14 publications

Combined time‐series resistivity and geochemical tracer techniques to examine submarine groundwater discharge at Dor Beach, Israel

Combined time‐series resistivity and geochemical tracer techniques to examine submarine groundwater discharge at Dor Beach, Israel

Submarine groundwater discharge and seawater circulation in a subterranean estuary beneath a tidal flat

Submarine groundwater discharge to Tampa Bay: Nutrient fluxes and biogeochemistry of the coastal aquifer

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