Surface water–groundwater exchange in transitional coastal environments by airborne electromagnetics: The Venice Lagoon example

Viezzoli, Andrea; Tosi, Luigi; Teatini, Pietro; Silvestri, S.

doi:10.1029/2009gl041572

Cited by 84 publications

(49 citation statements)

References 25 publications

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“…This holds for both the surface and subsurface environments. Investigations carried out over recent years Viezzoli et al, 2010) revealed that fresh groundwater resources are found at quite low depths, i.e., 30-40 m and even less than 10 m beneath the lagoon bottom. Like the hydrogeological settings of other lagoons (e.g., Santos et al, 2008), the silty-clayey layer marking the boundary between the marine Holocene and continental Pleistocene deposits precludes or at least reduces the vertical leakage of the salt waters downward into the un- derlying freshwater aquifers.…”

Section: Main Insightsmentioning

confidence: 99%

Hydrogeological effects of dredging navigable canals through lagoon shallows. A case study in Venice

Teatini

Isotton²,

Nardean

et al. 2017

Hydrol. Earth Syst. Sci.

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Abstract. For the first time a comprehensive investigation has been carried out to quantify the possible effects of dredging a navigable canal on the hydrogeological system underlying a coastal lagoon. The study is focused on the Venice Lagoon, Italy, where the port authority is planning to open a new 10 m deep and 3 km long canal to connect the city passenger terminal to the central lagoon inlet, thus avoiding the passage of large cruise ships through the historic center of Venice. A modeling study has been developed to evaluate the short (minutes), medium (months), and long (decades) term processes of water and pollutant exchange between the shallow aquifer system and the lagoon, possibly enhanced by the canal excavation, and ship wakes. An in-depth characterization of the lagoon subsurface along the channel has supported the numerical modeling. Piezometer and sea level records, geophysical acquisitions, laboratory analyses of groundwater and sediment samples (chemical analyses and ecotoxicity testing), and the outcome of 3-D hydrodynamic and computational fluid dynamic (CFD) models have been used to set up and calibrate the subsurface multi-model approach. The numerical outcomes allow us to quantify the groundwater volume and estimate the mass of anthropogenic contaminants (As, Cd, Cu, Cr, Hg, Pb, Se) likely leaked from the nearby industrial area over the past decades, and released into the lagoon from the canal bed by the action of depression waves generated by ships. Moreover, the model outcomes help to understand the effect of the hydrogeological layering on the propagation of the tidal fluctuation and salt concentration into the shallow brackish aquifers underlying the lagoon bottom.

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Section: Main Insightsmentioning

confidence: 99%

Hydrogeological effects of dredging navigable canals through lagoon shallows. A case study in Venice

Teatini

Isotton²,

Nardean

et al. 2017

Hydrol. Earth Syst. Sci.

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“…This is particularly true for data collected by airborne electromagnetic methods (AEM) because they can be collected quickly, densely, and at a relatively low cost for the very large spatial coverage (Steuer et al, 2008;Viezzoli et al, 2010b;Abraham et al, 2012;Faneca Sànchez et al, 2012;Refsgaard et al, 2014;Munday et al, 2015). Large-scale AEM (or ground-based EM) investigations have been used to delineate aquifers, aquitards, and buried valleys or other structures containing aquifers Jørgensen et al, 2003;Abraham et al, 2012;Oldenborger et al, 2013), to assess aquifer vulnerability Foged et al, 2014), to map saltwater intrusion (Fitterman and Deszcz-Pan, 1998;Viezzoli et al, 2010b;Lawrie et al, 2012;Herckenrath et al, 2013b), and to map freshwater resources (Steuer et al, 2008;Faneca Sànchez et al, 2012;Munday et al, 2015).…”

Section: Informing Hydrologic Models With Geophysicsmentioning

confidence: 99%

Testing alternative uses of electromagnetic data to reduce the prediction error of groundwater models

Christensen¹,

Christensen²,

Ferré³

2016

Hydrol. Earth Syst. Sci.

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Abstract. In spite of geophysics being used increasingly, it is often unclear how and when the integration of geophysical data and models can best improve the construction and predictive capability of groundwater models. This paper uses a newly developed HYdrogeophysical TEst-Bench (HYTEB) that is a collection of geological, groundwater and geophysical modeling and inversion software to demonstrate alternative uses of electromagnetic (EM) data for groundwater modeling in a hydrogeological environment consisting of various types of glacial deposits with typical hydraulic conductivities and electrical resistivities covering impermeable bedrock with low resistivity (clay). The synthetic 3-D reference system is designed so that there is a perfect relationship between hydraulic conductivity and electrical resistivity. For this system it is investigated to what extent groundwater model calibration and, often more importantly, model predictions can be improved by including in the calibration process electrical resistivity estimates obtained from TEM data. In all calibration cases, the hydraulic conductivity field is highly parameterized and the estimation is stabilized by (in most cases) geophysics-based regularization.For the studied system and inversion approaches it is found that resistivities estimated by sequential hydrogeophysical inversion (SHI) or joint hydrogeophysical inversion (JHI) should be used with caution as estimators of hydraulic conductivity or as regularization means for subsequent hydrological inversion. The limited groundwater model improvement obtained by using the geophysical data probably mainly arises from the way these data are used here: the alternative inversion approaches propagate geophysical estimation errors into the hydrologic model parameters. It was expected that JHI would compensate for this, but the hydrologic data were apparently insufficient to secure such compensation. With respect to reducing model prediction error, it depends on the type of prediction whether it has value to include geophysics in a joint or sequential hydrogeophysical model calibration. It is found that all calibrated models are good predictors of hydraulic head. When the stress situation is changed from that of the hydrologic calibration data, then all models make biased predictions of head change. All calibrated models turn out to be very poor predictors of the pumping well's recharge area and groundwater age. The reason for this is that distributed recharge is parameterized as depending on estimated hydraulic conductivity of the upper model layer, which tends to be underestimated. Another important insight from our analysis is thus that either recharge should be parameterized and estimated in a different way, or other types of data should be added to better constrain the recharge estimates.

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“…For example, this is fairly common at landfills and waste dump sites [1][2][3], saline disposal basins [4], seawater inundation along coastal aquifers [5], and in estuaries [6][7][8][9][10][11]. Typically, when saltwater and freshwater are in contact with each other, the groundwater flow is due to natural hydraulic gradients, and the movement of the fluid is termed "forced" convection.…”

Section: Forced Free and Mixed Convective Flowmentioning

confidence: 99%

Stochastic Nature of Salt Mass Transport in Porous Media Under Unstable Conditions

Mamoua¹,

Pandit²,

Heck³

2017

Hydrol Current Res

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The two main transport mechanisms that occur simultaneously under unstable flow conditions are transport of saltwater from an overlying salt source to the porous media, and transport of salt through the porous media. These mechanisms were simultaneously studied through two fixed mass experiments conducted over 15 days. The transport through the porous media was also studied via three continuous injection experiments lasting between 5 to 29 days. There was no hydraulic gradient across the porous media in any of the experiments. Experiments were conducted in a 1 cm thick plexiglass rectangular sand column (1.70 m × 0.61 m × 0.61 m). The saline source concentration was 36 g/l, and the source heights were 4.5 cm. The sand porosity and hydraulic conductivity were 32% and 9.0 m/d, respectively. The rate of mass transport from the source to the porous media was observed by measuring the salt concentration within the source, while the salt transport through the porous media was documented by measuring breakthrough curves at five locations within the sand column. Fixed mass experiment results, using mass analysis, showed that the salt transport from the source to the porous media was deterministic since both experiments produced identical rates of mass transport from the source to the porous media, the salt transport through the porous media was stochastic since the observed breakthrough curves at the five locations were considerably different. The breakthrough curves measured in three identical continuous injection experiments were also very different supporting the results of the fixed mass experiments. The implications of these findings are that, under unstable conditions, one can predict the salt mass that would enter from a salt source into the underlying porous media with certainty, one cannot predict the rate or pattern of salt transport through the porous media itself.

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Surface water–groundwater exchange in transitional coastal environments by airborne electromagnetics: The Venice Lagoon example

Cited by 84 publications

References 25 publications

Hydrogeological effects of dredging navigable canals through lagoon shallows. A case study in Venice

Hydrogeological effects of dredging navigable canals through lagoon shallows. A case study in Venice

Testing alternative uses of electromagnetic data to reduce the prediction error of groundwater models

Stochastic Nature of Salt Mass Transport in Porous Media Under Unstable Conditions

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