scholarly journals High-Resolution Electrical Resistivity Tomography (ERT) to Characterize the Spatial Extension of Freshwater Lenses in a Salinized Coastal Aquifer

Water ◽  
2018 ◽  
Vol 10 (8) ◽  
pp. 1067 ◽  
Author(s):  
Nicolas Greggio ◽  
Beatrice Giambastiani ◽  
Enrico Balugani ◽  
Chiara Amaini ◽  
Marco Antonellini
Keyword(s):  
Electrical Resistivity ◽  
High Resolution ◽  
Electrical Resistivity Tomography ◽  
Decision Makers ◽  
Shallow Aquifer ◽  
Electrode Spacing ◽  
Coastal Zones ◽  
Aquifer Recharge ◽  
Resistivity Tomography ◽  
Freshwater Lenses

High-resolution electrical resistivity tomography (ERT) with electrode spacing of 1 m proved to be an effective methodology to characterize ephemeral, sparse, and discontinuous freshwater lenses within the almost completely salinized shallow aquifer of the low coastal zone near Ravenna. ERT profiles with a vertical resolution of 0.25–0.5 m, once calibrated with groundwater data (water table depth and electrical conductivity) collected in multi-level sampler systems at the same spatial resolution, are reliable and provide repeatable measurements in time. The ERT methodology allows for fast data acquisition over large areas and it also permits the study of the evolution in time of freshwater availability in coastal zones, which is important for local ecosystems and soil resources. This makes high-resolution ERT a valid tool to aid local stakeholders and decision makers to effectively manage freshwater lenses, and guarantee their preservation or augmentation by means of managed aquifer recharge.

scholarly journals Two-dimensional Electrical Resistivity Tomography of Bitumen Occurrence in Agbabu, Southwest Nigeria

2019 ◽  
pp. 1-9
Author(s):  
O. F. Ogunlana ◽  
O. M. Alile ◽  
O. J. Airen
Keyword(s):  
Electrical Resistivity ◽  
Apparent Resistivity ◽  
Electrical Resistivity Tomography ◽  
Electrode Spacing ◽  
Southwestern Nigeria ◽  
Resistivity Tomography ◽  
2D Inversion ◽  
Earth Resistivity ◽  
Southwest Nigeria ◽  
Resistivity Meter

The Electrical Resistivity Tomography (ERT) data was acquired within the area suspected to have high potential for bitumen occurrence using the Wenner-Schlumberger configuration in Agbabu, southwestern Nigeria. PASI 16GL-N Earth resistivity meter instrument was used to acquire data along five (5) traverses with 5m electrode spacing and traverses length of 150m. The apparent resistivity values obtained was processed using RES2DINV software which helped to automatically obtain the 2D inversion model of the subsurface. This study has shown the occurrence of bitumen between the depth of 13.4m and 9.93m for Traverses 1, 2, 3 and Traverses 4, 5 respectively in a 2-Dimensional electrical resistivity images for boreholes with a depth of about 18m. The results indicate that the bitumen is characterized by good lateral continuity and is sufficiently thick for commercial exploitation.

scholarly journals Exploring the regolith with electrical resistivity tomography in largescale surveys: electrode spacing related issues and possibility

2020 ◽  
Author(s):  
Laurent Gourdol ◽  
Rémi Clément ◽  
Jérôme Juilleret ◽  
Laurent Pfister ◽  
Christophe Hissler
Keyword(s):  
Electrical Resistivity ◽  
Apparent Resistivity ◽  
Large Scale ◽  
Electrical Resistivity Tomography ◽  
Subsurface Layer ◽  
Electrode Spacing ◽  
High Resistivity ◽  
Constant Thickness ◽  
Resistivity Tomography

Abstract. Within the Critical Zone, regolith plays a key role in the fundamental hydrological functions of water collection, storage, mixing and release. Electrical Resistivity Tomography (ERT) is recognized as a remarkable tool for characterizing the geometry and properties of the regolith, overcoming limitations inherent to conventional borehole-based investigations. For exploring shallow layers, a small electrode spacing (ES) will provide a denser set of apparent resistivity measurements of the subsurface. As this option is cumbersome and time-consuming, smaller ES – albeit offering poorer shallow apparent resistivity data – are often preferred for large horizontal ERT surveys. To investigate the negative trade-off between larger ES and reduced accuracy of the inverted ERT images for shallow layers, we use a set of synthetic conductive/resistive/conductive three-layered soil–saprock/saprolite–bedrock models in combination with a reference field dataset. Our results suggest that an increase in ES causes a deterioration of the accuracy of the inverted ERT images in terms of both resistivity distribution and interface delineation and, most importantly, that this degradation increases sharply when the ES exceeds the thickness of the top subsurface layer. This finding, which is obvious for the characterization of shallow layers, is also relevant even when solely aiming for the characterization of deeper layers. We show that an oversized ES leads to overestimations of depth to bedrock and that this overestimation is even more important for subsurface structures with high resistivity contrast. To overcome this limitation, we propose adding interpolated levels of surficial apparent resistivity relying on a limited number of ERT profiles with a smaller ES. We demonstrate that our protocol significantly improves the accuracy of ERT profiles when using large ES, provided that the top layer has a rather constant thickness and resistivity. For the specific case of large-scale ERT surveys the proposed upgrading procedure is cost-effective in comparison to protocols based on small ES.

High-resolution electrical resistivity tomography to investigate the origin of the Tsugaru-Juniko Lakes : An example near the Ao-ike

2021 ◽  
Vol 58 (3) ◽  
pp. 109-117
Author(s):  
Ching-Ying TSOU ◽  
Kousei YAMABE ◽  
Daisuke HIGAKI ◽  
Takayoshi SASAGAWA ◽  
Tomo KIRIU ◽  
...  
Keyword(s):  
Electrical Resistivity ◽  
High Resolution ◽  
Electrical Resistivity Tomography ◽  
Resistivity Tomography

scholarly journals Laboratory Studies Using Electrical Resistivity Tomography and Fiber Optic Techniques to Detect Seepage Zones in River Embankments

Geosciences ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 69
Author(s):  
Azadeh Hojat ◽  
Maddalena Ferrario ◽  
Diego Arosio ◽  
Marco Brunero ◽  
Vladislav Ivov Ivanov ◽  
...  
Keyword(s):  
Electrical Resistivity ◽  
Electrical Resistivity Tomography ◽  
Fiber Optic ◽  
Time Lapse ◽  
Electrode Spacing ◽  
Short Delay ◽  
Resistivity Tomography ◽  
Temperature Changes ◽  
Pros And Cons ◽  
Wenner Array

We present the results of laboratory experiments on a down-scaled river levee constructed with clayey material collected from a river embankment where a permanent resistivity instrument has operated since 2015. To create potential seepages through the levee, two zones (5 × 4 cm and 10 × 2 cm) were filled with sand during the levee construction. Electrical resistivity tomography (ERT) technique and Fiber Bragg Grating (FBG) technology were used to study time-lapse variations due to seepage. The ERT profile was spread on the levee crest and the Wenner array with unit electrode spacing a = 3 cm was used. Six organic modified ceramics (ORMOCER) coated 250 μm-diameter fibers were deployed in different parts of the levee. Time-lapse measurements were performed for both techniques from the beginning of each experiment when water was added to the river side until the water was continuously exiting from the seepage zones. The results showed that ERT images could detect seepages from the early stages. Although with a short delay compared to ERT, fiber optic sensors also showed their ability to detect water infiltrations by measuring temperature changes. Both technologies being successful, a discussion about respective peculiarities and pros and cons is proposed to suggest some criteria in choosing the proper technique according to the specific needs.

scholarly journals Interpretasi Electrical Resistivity Tomography (ERT) untuk Pendugaan Air Tanah Dangkal pada Formasi Gunungapi Muda

2020 ◽  
Vol 3 (1) ◽  
pp. 49 ◽  
Author(s):  
Erik Febriarta ◽  
Suswanti Suswanti ◽  
Sembodo Noviandaru
Keyword(s):  
Electrical Resistivity ◽  
Electrical Resistivity Tomography ◽  
Soil Surface ◽  
Igneous Rocks ◽  
Shallow Aquifer ◽  
Rock Outcrops ◽  
Resistivity Tomography ◽  
Surface Appearance ◽  
Hydrogeological Characteristics ◽  
Groundwater Basin

Aquifers or groundwater saturated areas in the slope morphology of Merapi volcano are relatively thin due to massive rock outcrops above the surface. Because these massive igneous rocks dominate the local geological appearance, the groundwater potential on the upper foot slope is relatively lower than the lower one that has thicker aquifer materials (sand). This study was designed to investigate the thickness of potential groundwater and identify the aquifer materials by geoelectrical methods using the Electrical Resistivity Tomography (ERT) configuration. ERT has several advantages, including its ability to present multi-log lithology vertically and produce a more detailed surface appearance. In this study, rock resistivity values were measured with a survey line stretching across 250 m. The geoelectrical imaging produced actual values (potential values) of the rock resistivities through the matching curve and inversion techniques. Afterward, the actual resistivities were matched with the standard electrical resistivity of rocks and their respective hydrogeological characteristics, i.e., the capacity to store and transmit water. Interpretation on rock resistivities detected groundwater at a depth of 0.5-12 m in Manisrenggo. This shallow aquifer has an impermeable layer composed of igneous rocks, which are massive breccia, that lie in one layer of sand. According to the Groundwater Basin Map, these rock formations are part of the Karanganyar-Boyolali Groundwater Basin. The shallow aquifers and hydraulic gradient lead to the emergence of seeps or flushes on the soil surface.

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