scholarly journals Calibration of seawater intrusion models: Inverse parameter estimation using surface electrical resistivity tomography and borehole data

2014 ◽  
Vol 50 (8) ◽  
pp. 6828-6849 ◽  
Author(s):  
J. Beaujean ◽  
F. Nguyen ◽  
A. Kemna ◽  
A. Antonsson ◽  
P. Engesgaard
Keyword(s):  
Electrical Resistivity ◽  
Parameter Estimation ◽  
Seawater Intrusion ◽  
Electrical Resistivity Tomography ◽  
Borehole Data ◽  
Resistivity Tomography

scholarly journals Identifying Changes in Sediment Texture along an Ephemeral Gravel-Bed Stream Using Electrical Resistivity Tomography 2D and 3D

2021 ◽  
Vol 11 (7) ◽  
pp. 3030
Author(s):  
Marcos A. Martínez-Segura ◽  
Carmelo Conesa-García ◽  
Pedro Pérez-Cutillas ◽  
Pedro Martínez-Pagán ◽  
Marco D. Vásconez-Maza
Keyword(s):  
Electrical Resistivity ◽  
Cross Sections ◽  
Electrical Resistivity Tomography ◽  
Environmental Changes ◽  
Subsurface Layer ◽  
Sediment Texture ◽  
Borehole Data ◽  
Resistivity Tomography ◽  
Gravel Bed ◽  
Basin Scale

Differences in deposit geometry and texture with depth along ephemeral gravel-bed streams strongly reflect fluctuations in bedload which are due to environmental changes at the basin scale and to morphological channel adjustments. This study combines electrical resistivity tomography (ERT) with datasets from borehole logs to analyse the internal geometry of channel cross-sections in a gravel-bed ephemeral stream (southeast Spain). The survey was performed through longitudinal and transverse profiles in the upper channel stretch, of 14 to 30 m in length and 3 to 6 m in depth, approximately. ERT values were correlated with data on sediment texture as grain size distribution, effective grain sizes, sorting, and particle shape (Zingg’s classification). The alluvial channel-fills showed the superposition of four layers with uneven thickness and arrangement: (1) the softer rocky substrate (<1000 Ω.m); (2) a thicker intermediate layer (1000 to 2000 Ω.m); and (3) an upper set composed of coarse gravel and supported matrix, ranging above 2000 Ω.m, and a narrow subsurface layer, which is the most resistive (>5000 Ω.m), corresponding to the most recent armoured deposits (gravel and pebbles). The ERT results coupled with borehole data allowed for determining the horizontal and vertical behaviour of the materials in a 3D model, facilitating the layer identification.

scholarly journals Time-lapse cross-hole electrical resistivity tomography (CHERT) for monitoring seawater intrusion dynamics in a Mediterranean aquifer

2019 ◽  
Author(s):  
Andrea Palacios ◽  
Juan José Ledo ◽  
Niklas Linde ◽  
Linda Luquot ◽  
Fabian Bellmunt ◽  
...  
Keyword(s):  
Electrical Conductivity ◽  
Electrical Resistivity ◽  
Seawater Intrusion ◽  
Electrical Resistivity Tomography ◽  
Low Cost ◽  
Heavy Rain ◽  
Time Lapse ◽  
Resistivity Tomography ◽  
Bulk Electrical Conductivity ◽  
Spatial Coverage

Abstract. Surface electrical resistivity tomography (ERT) is a widely used tool to study seawater intrusion (SWI). It is noninvasive and offers a high spatial coverage at a low cost, but it is strongly affected by decreasing resolution with depth. We conjecture that the use of CHERT (cross-hole ERT) can partly overcome these resolution limitations since the electrodes are placed at depth, which implies that the model resolution does not decrease in the zone of interest. The objective of this study is to evaluate the CHERT for imaging the SWI and monitoring its dynamics at the Argentona site, a well-instrumented field site of a coastal alluvial aquifer located 40 km NE of Barcelona. To do so, we installed permanent electrodes around boreholes attached to the PVC pipes to perform time-lapse monitoring of the SWI on a transect perpendicular to the coastline. After two years of monitoring, we observe variability of SWI at different time scales: (1) natural seasonal variations and aquifer salinization that we attribute to long-term drought and (2) short-term fluctuations due to sea storms or flooding in the nearby stream during heavy rain events. The spatial imaging of bulk electrical conductivity allows us to explain non-trivial salinity profiles in open boreholes (step-wise profiles really reflect the presence of fresh water at depth). By comparing CHERT results with traditional in situ measurements such as electrical conductivity of water samples and bulk electrical conductivity from induction logs, we conclude that CHERT is a reliable and cost-effective imaging tool for monitoring SWI dynamics.

scholarly journals Time-lapse cross-hole electrical resistivity tomography (CHERT) for monitoring seawater intrusion dynamics in a Mediterranean aquifer

2020 ◽  
Vol 24 (4) ◽  
pp. 2121-2139 ◽  
Author(s):  
Andrea Palacios ◽  
Juan José Ledo ◽  
Niklas Linde ◽  
Linda Luquot ◽  
Fabian Bellmunt ◽  
...  
Keyword(s):  
Electrical Conductivity ◽  
Electrical Resistivity ◽  
Seawater Intrusion ◽  
Electrical Resistivity Tomography ◽  
Low Cost ◽  
Heavy Rain ◽  
Time Lapse ◽  
Resistivity Tomography ◽  
Bulk Electrical Conductivity ◽  
Spatial Coverage

Abstract. Surface electrical resistivity tomography (ERT) is a widely used tool to study seawater intrusion (SWI). It is noninvasive and offers a high spatial coverage at a low cost, but its imaging capabilities are strongly affected by decreasing resolution with depth. We conjecture that the use of CHERT (cross-hole ERT) can partly overcome these resolution limitations since the electrodes are placed at depth, which implies that the model resolution does not decrease at the depths of interest. The objective of this study is to test the CHERT for imaging the SWI and monitoring its dynamics at the Argentona site, a well-instrumented field site of a coastal alluvial aquifer located 40 km NE of Barcelona. To do so, we installed permanent electrodes around boreholes attached to the PVC pipes to perform time-lapse monitoring of the SWI on a transect perpendicular to the coastline. After 2 years of monitoring, we observe variability of SWI at different timescales: (1) natural seasonal variations and aquifer salinization that we attribute to long-term drought and (2) short-term fluctuations due to sea storms or flooding in the nearby stream during heavy rain events. The spatial imaging of bulk electrical conductivity allows us to explain non-monotonic salinity profiles in open boreholes (step-wise profiles really reflect the presence of freshwater at depth). By comparing CHERT results with traditional in situ measurements such as electrical conductivity of water samples and bulk electrical conductivity from induction logs, we conclude that CHERT is a reliable and cost-effective imaging tool for monitoring SWI dynamics.

Application of Electrical Resistivity Tomography and Ground Penetrating Radar to assess salinity in a coastal aquifer with tidally-driven saline recirculation cell

2020 ◽  
Author(s):  
Jesús Fernández Águila ◽  
Mark McDonnell ◽  
Raymond Flynn ◽  
Alastair Ruffell ◽  
Eric Benner ◽  
...  
Keyword(s):  
Electrical Resistivity ◽  
Seawater Intrusion ◽  
Ground Penetrating Radar ◽  
Water Samples ◽  
Electrical Resistivity Tomography ◽  
High Water ◽  
Fresh Groundwater ◽  
Resistivity Tomography ◽  
Tidally Driven ◽  
Ground Penetrating

&lt;p&gt;Seawater intrusion is a major issue worldwide, as coastal aquifers often act as the primary source of drinking water for more than one billion people. With climate change and projected population increases in coastal areas, this problem is anticipated to become more pressing over the next decades. Effective site characterisation strategies provide a crucial component in understanding subsurface saltwater migration. Density differences cause freshwater to float on seawater creating the classical saltwater intrusion saline wedge. However, tides often control coastal groundwater dynamics causing the emergence of an upper saline recirculation cell beneath the intertidal zone (Intertidal Recirculation Cell, IRC). Here we present the application of Electrical Resistivity Tomography (ERT) and Ground Penetrating Radar (GPR) techniques to characterize the coastal sand aquifer underlying Benone Strand (Magilligan, Northern Ireland) where tides induce an IRC. The aquifer is approximately 20 m thick and rests directly on Lr. Jurassic mudstones.&lt;/p&gt;&lt;p&gt;2D ERT profiles were generated at Benone beach using the SYSCAL Pro 72 ERI system (Iris Instruments). Two different array configurations (Wenner-Schlumberger and dipole-dipole) were used to provide both improved horizontal and vertical resolution. Because of the homogeneity of the sand, the ERT profiles made it possible to clearly define the configuration of the IRC and the fresh groundwater discharging &amp;#8220;tube&amp;#8221;. The presence of the tidally-driven recirculation cell causes fresh groundwater to flow below the IRC (&amp;#8220;discharge tube&amp;#8221;) and discharge in the vicinity of the low water mark. ERT data suggest that the IRC has a resistivity of approximately 1 &amp;#937;m and a thickness of 8 m. Resistivity increases below the IRC, but declines moving towards the low water mark. These findings suggest a possible mixing zone between saline water and the freshwater discharge. To verify the accuracy of the resistivity values measured in the ERT profiles, water samples were collected at various distances along a perpendicular transect from the high water mark to the low water mark. The electrical conductivities of the water samples were measured and compared with the resistivities obtained in the ERT profiles using Archie's law. Similar values were obtained in both cases.&lt;/p&gt;&lt;p&gt;A MAL&amp;#197; ground penetrating radar system, operating at 50 MHz, 100 MHz and 500 MHz, was used to collect 2D GPR profiles at Benone beach from the low tide mark to beyond the high water mark. Findings suggested that the IRC attenuated the radar signal in all cases. However, GPR profiles were crucially important to demarcate the interfaces between freshwater and saltwater near the ground surface. GPR profiles obtained using higher frequencies (500 MHz) were the most informative.&lt;/p&gt;&lt;p&gt;The research work carried out at Magilligan allows us to conclude that the application of ERT and GPR techniques is effective in delineating seawater intrusion in aquifers where tides create an IRC. In addition, ERT profiles very clearly identified the IRC through field measurements (which in most cases is studied through numerical models and laboratory tests).&lt;/p&gt;

scholarly journals Characterization of aquifer system using electrical resistivity tomography (ERT) and induced polarisation (IP) techniques

2021 ◽  
Vol 880 (1) ◽  
pp. 012025
Author(s):  
N Akhtar ◽  
M S Mislan ◽  
M I Syakir ◽  
M T Anees ◽  
M S M Yusuff
Keyword(s):  
Electrical Resistivity ◽  
Electrical Resistivity Tomography ◽  
Imaging System ◽  
Borehole Data ◽  
Resistivity Tomography ◽  
Aquifer System ◽  
Saturation Zone ◽  
Average Percentage ◽  
Aquifer Systems ◽  
Freshwater Resource

Abstract Groundwater plays a major role as an alternative freshwater resource for irrigation and industrial purposes. This study aimed to characterize the subsurface of aquifer systems in TelukIntan district, Perak, Malaysia using Electrical Resistivity Tomography (ERT) and Induced Polarization (IP) methods. The horizontal profiling (TL1 and TL2) was conducted at length of 400 m. The estimated depth is 150 m below ground level (b.g.l.). An ABEM SAS 4000 Terrameter and ABEM LUND ES464 Imaging System were applied to create a resistivity pseudo-section using polar-dipole configuration. The collected geo-electrical data was interpreted using RESIST software with partial curve matching and computer iteration. ERT and IP survey profile results were validated with in-situ borehole data from borehole 2 (B2). Eleven samples of soil profile were collected at depth from 5.6 m to 61.2 m, with average percentage of sand, silt and clay are 93.77 %, 5.78 % and 0.02 %, respectively. The geology of subsurface settings is the key factor in determining the aquifer system characterized by interlayer sand-silt sequence indicating the saturation zone of aquifer underlain by shale at the bottom. Further study on hydraulics perspective is important to understand the overall capacity of the aquifer.

scholarly journals Evaluating the Application of Electrical Resistivity Tomography for Investigating Seawater Intrusion

Electronics ◽  
2018 ◽  
Vol 7 (7) ◽  
pp. 107 ◽  
Author(s):  
Tung-Tsan Chen ◽  
Yin-Chun Hung ◽  
Ming-Wei Hsueh ◽  
Yung-Hsin Yeh ◽  
Ko-Wei Weng
Keyword(s):  
Electrical Resistivity ◽  
Seawater Intrusion ◽  
Electrical Resistivity Tomography ◽  
Resistivity Tomography
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