Hydrogeophysical exploration of three-dimensional salinity anomalies with the time-domain electromagnetic method (TDEM)

Publication: Research - peer-reviewJournal article – Annual report year: 2010

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Hydrogeophysical exploration of three-dimensional salinity anomalies with the time-domain electromagnetic method (TDEM). / Bauer-Gottwein, Peter; Gondwe, Bibi Ruth Neuman; Christiansen, Lars; Herckenrath, Daan; Kgotlhang, L.; Zimmermann, S.

In: Journal of Hydrology, Vol. 380, No. 3-4, 2010, p. 318-329.

Publication: Research - peer-reviewJournal article – Annual report year: 2010

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Bauer-Gottwein, Peter; Gondwe, Bibi Ruth Neuman; Christiansen, Lars; Herckenrath, Daan; Kgotlhang, L.; Zimmermann, S. / Hydrogeophysical exploration of three-dimensional salinity anomalies with the time-domain electromagnetic method (TDEM).

In: Journal of Hydrology, Vol. 380, No. 3-4, 2010, p. 318-329.

Publication: Research - peer-reviewJournal article – Annual report year: 2010

Bibtex

@article{33c9dfab2ed24f8ca7b0f732ed11b117,
title = "Hydrogeophysical exploration of three-dimensional salinity anomalies with the time-domain electromagnetic method (TDEM)",
publisher = "Elsevier BV",
author = "Peter Bauer-Gottwein and Gondwe, {Bibi Ruth Neuman} and Lars Christiansen and Daan Herckenrath and L. Kgotlhang and S. Zimmermann",
year = "2010",
doi = "10.1016/j.jhydrol.2009.11.007",
volume = "380",
number = "3-4",
pages = "318--329",
journal = "Journal of Hydrology",
issn = "0022-1694",

}

RIS

TY - JOUR

T1 - Hydrogeophysical exploration of three-dimensional salinity anomalies with the time-domain electromagnetic method (TDEM)

A1 - Bauer-Gottwein,Peter

A1 - Gondwe,Bibi Ruth Neuman

A1 - Christiansen,Lars

A1 - Herckenrath,Daan

A1 - Kgotlhang,L.

A1 - Zimmermann,S.

AU - Bauer-Gottwein,Peter

AU - Gondwe,Bibi Ruth Neuman

AU - Christiansen,Lars

AU - Herckenrath,Daan

AU - Kgotlhang,L.

AU - Zimmermann,S.

PB - Elsevier BV

PY - 2010

Y1 - 2010

N2 - The time-domain electromagnetic method (TDEM) is widely used in groundwater exploration and geological mapping applications. TDEM measures subsurface electrical conductivity, which is strongly correlated with groundwater salinity. TDEM offers a cheap and non-invasive option for mapping saltwater intrusion and groundwater salinization. Traditionally, TDEM data is interpreted using one-dimensional layered-earth models of the subsurface. However, most saltwater intrusion and groundwater salinization phenomena are characterized by three-dimensional anomalies. To fully exploit the information content of TDEM data in this context, three-dimensional modeling of the TDEM response is required. We present a finite-element solution for three-dimensional forward modeling of TDEM responses from arbitrary subsurface electrical conductivity distributions. The solution is benchmarked against standard layered-earth models and previously published three-dimensional forward TDEM modeling results. Concentration outputs from a groundwater flow and salinity transport model are converted to subsurface electrical conductivity using standard petrophysical relationships. TDEM responses over the resulting subsurface electrical conductivity distribution are generated using the three-dimensional TDEM forward model. The parameters of the hydrodynamic model are constrained by matching observed and simulated TDEM responses. As an application example, a field dataset of ground-based TDEM data from an island in the Okavango Delta is presented. Evaporative salt enrichment causes a strong salinity anomaly under the island. We show that the TDEM field data cannot be interpreted in terms of standard one-dimensional layered-earth TDEM models, because of the strongly three-dimensional nature of the salinity anomaly. Three-dimensional interpretation of the field data allows for detailed and consistent mapping of this anomaly and makes better use of the information contained in the TDEM field dataset.

AB - The time-domain electromagnetic method (TDEM) is widely used in groundwater exploration and geological mapping applications. TDEM measures subsurface electrical conductivity, which is strongly correlated with groundwater salinity. TDEM offers a cheap and non-invasive option for mapping saltwater intrusion and groundwater salinization. Traditionally, TDEM data is interpreted using one-dimensional layered-earth models of the subsurface. However, most saltwater intrusion and groundwater salinization phenomena are characterized by three-dimensional anomalies. To fully exploit the information content of TDEM data in this context, three-dimensional modeling of the TDEM response is required. We present a finite-element solution for three-dimensional forward modeling of TDEM responses from arbitrary subsurface electrical conductivity distributions. The solution is benchmarked against standard layered-earth models and previously published three-dimensional forward TDEM modeling results. Concentration outputs from a groundwater flow and salinity transport model are converted to subsurface electrical conductivity using standard petrophysical relationships. TDEM responses over the resulting subsurface electrical conductivity distribution are generated using the three-dimensional TDEM forward model. The parameters of the hydrodynamic model are constrained by matching observed and simulated TDEM responses. As an application example, a field dataset of ground-based TDEM data from an island in the Okavango Delta is presented. Evaporative salt enrichment causes a strong salinity anomaly under the island. We show that the TDEM field data cannot be interpreted in terms of standard one-dimensional layered-earth TDEM models, because of the strongly three-dimensional nature of the salinity anomaly. Three-dimensional interpretation of the field data allows for detailed and consistent mapping of this anomaly and makes better use of the information contained in the TDEM field dataset.

U2 - 10.1016/j.jhydrol.2009.11.007

DO - 10.1016/j.jhydrol.2009.11.007

JO - Journal of Hydrology

JF - Journal of Hydrology

SN - 0022-1694

IS - 3-4

VL - 380

SP - 318

EP - 329

ER -