scholarly journals IMAGING SEAWATER INTRUSION IN COASTAL ZONE OF KAVALA (N. GREECE) WITH ELECTRICAL RESISTIVITY TOMOGRAPHY

2017 ◽  
Vol 43 (4) ◽  
pp. 1802 ◽  
Author(s):  
Y. Mertzanides ◽  
N. Economou ◽  
H. Hamdan ◽  
A. Vafidis
Keyword(s):  
Electrical Resistivity ◽  
Coastal Zone ◽  
Seawater Intrusion ◽  
Agricultural Development ◽  
Electrical Resistivity Tomography ◽  
Geophysical Investigation ◽  
Salt Intrusion ◽  
Resistivity Tomography ◽  
Rational Management ◽  
A Site

The needs for water supply in the western coastal zone of Kavala (N. Greece) have been rapidly increased during the last decades because of the high tourist and agricultural development. This resulted to a number of wells that drilled along the coastline. During summer period, when human and irrigation consumptions are maximized, phenomena of groundwater salinization are observed. Although restrictions to new drillings have been taken, salinization in some aquatic systems of the area tends to become a major environmental and economical issue. The only available information till now was a timeseries of groundwater electrical conductivity measurements, in some of the wells of the area. This information is useful but not adequate for the study of the salt intrusion mechanism. Geophysical investigation was carried out and electrical resistivity tomography (ERT) was chosen as the most appropriate technique for the case. The geophysical survey was set in a site between the coastline and an existing borehole. The 2D ERT profiles gave a clear image of geoelectrical heterogeneities, associated with seawater intrusion in the coastal aquifers, contributing to future measures towards a rational management of ground water resources in the area.

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

<p>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.</p><p>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 “tube”. The presence of the tidally-driven recirculation cell causes fresh groundwater to flow below the IRC (“discharge tube”) and discharge in the vicinity of the low water mark. ERT data suggest that the IRC has a resistivity of approximately 1 Ωm 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.</p><p>A MALÅ 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.</p><p>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).</p>

scholarly journals Electrical Resistivity Tomography And Induced Polarization Study For Groundwater Exploration In The Agricultural Development Areas of Brunei Darussalam

2021 ◽  
Author(s):  
Lieyana Azffri ◽  
Stefan Herwig Gödeke ◽  
Mohammad Faizan Ibrahim
Keyword(s):  
Electrical Resistivity ◽  
Agricultural Development ◽  
Electrical Resistivity Tomography ◽  
Groundwater Exploration ◽  
Induced Polarization ◽  
Resistivity Tomography ◽  
Well Drilling ◽  
Brunei Darussalam ◽  
Groundwater Yield ◽  
2D Resistivity

Abstract Electrical Resistivity Tomography (ERT) and Induced Polarization (IP) study was carried out for groundwater exploration at eight agricultural development areas in Brunei Darussalam. The study was undertaken to meet the growing demands of water supply in the Brunei agricultural sector, particularly for paddy field irrigation. A total of nineteen survey lines with survey lengths of up to 800 m and investigation depths of up to 150 m below ground level were conducted to delineate subsurface geological structures, formations and aquifer zones in the study area. Aquifer zones with resistivity values ranging from 1 to 100 ohm-m and chargeability values of less than 1 mV/V were detected in all surveyed locations. New groundwater well drilling was conducted at two of the surveyed sites based on interpretations of 2D resistivity and chargeability inversion models. Water well drilling encountered aquifer zones, which were primarily in sandy layers. Hydraulic tests revealed groundwater yields of 4.3 and 288 m³/day. Estimated transmissivity values of the aquifer units based on pumping tests are 0.53 and 109 m²/day, while their hydraulic conductivity values are 0.05 and 2.75 m/day. Estimated parameters of the aquifer units indicate weak to moderate groundwater yield for withdrawal and distribution for irrigation purposes at the investigated sites. The present study helped decision-makers take suitable measures for placing future irrigation wells and achieve significant groundwater exploration results in the study area.

scholarly journals IDENTIFICATION AND EVALUATION OF FRACTURES USING ELECTRICAL RESISTIVITY TOMOGRAPHY IN THE VICINITY OF THE AXIS OF THE HUAMANTANGA DAM – LIMA – PERU

2018 ◽  
Vol 36 (2) ◽  
pp. 111
Author(s):  
Christ Jesus Barriga Paria ◽  
Jorge Pantaleon Barriga Gamarra
Keyword(s):  
Electrical Resistivity ◽  
Electrical Resistivity Tomography ◽  
The Other ◽  
Management Technique ◽  
Geophysical Investigation ◽  
Electrical Method ◽  
Resistivity Tomography ◽  
Outer Slope ◽  
Resistivity Measurements ◽  
High Infiltration

ABSTRACT. Huamantanga located approximately 3390 msnm in the central highlands of Peru, a district that promotes the sowing and harvesting of water called “mamanteo”, Inca ancestral water management technique to derive water from a ravine during the rainy season, to places with a high infiltration. On the other hand the construction of a dam, named with the same name, was built for the storage water due to the increase of the agrarian activities, nevertheless worrisome leaks were observed by which electrical resistivity tomography in these possible zones were realized Distributed four profiles, one parallel to the axis of the dam, 10 to 15 meters upstream of the first profile, on the outer slope and the fourth profile approximately 10 meters above the spring. In this way, the resistivity measurements were performed for each of the four lines of Tomographic Electric, in order to obtain detailed information of the stratigraphy in the study area and to identify the georesistive anomalies caused by tectonic or geological faults, Reflect as areas of low resistivities or anomalies. Analyzed the area of study were found considerable local fractures which were recommended to be quickly waterproofed because the risk of infiltrations is latent. Keywords: infiltration, fracture, geophysical investigation, electrical method.    RESUMO. Huamantanga localizado aproximadamente a 3390 msnm no centro da serra do Peru, distrito que promove o cultivo e colheita de água chamado de “mamanteo”, atividade incaica para derivar um fluxo de água durante a estação chuvosa, para locais com alta infiltração. Além disso, a construção de uma barragem, chamado pelo mesmo nome, foi construído para armazenar água devido ao aumento das atividades agrícolas, foram observados, no entanto vazamentos preocupantes foram observados para os quais foram realizados Tomografia Eléctrica nessas áreas potenciais, foram distribuído quatro perfis, uma paralela ao eixo da barragem de 10 a 15 metros a montante a partir do primeiro perfil, no lado exterior e o quarto perfil aproximadamente 10 metros acima da fonte de água. Assim, as medições de resistividade foram feitas para cada uma das 4 linhas de Tomografia Eléctrica, a fim de obter informações pormenorizadas sobre a estratigrafia na área de estudo e identificar anomalias georesistivas causadas por tectônismo ou falhas geológicas, que refletem como áreas de resistividades tão baixas ou anomalias. Analisada a área de estudo foram encontrados fratura locais consideráveis, que foram recomendadas a ser impermeabilizadas rapidamente, porque o risco de infiltrações é latente.  Palavras-chave: infiltração, fratura, investigação geofísica, método elétrico.    

2D ELECTRICAL RESISTIVITY TOMOGRAPHY FOR THE ASSESSMENT OF MINERALS’ OCCURRENCES IN UGONEKI, EDO STATE, SOUTH-SOUTH, NIGERIA

2021 ◽  
Vol 5 (2) ◽  
pp. 635-639
Author(s):  
Y. S. Onifade ◽  
V. B. Olaseni ◽  
I. G. Baoku ◽  
C. Eravwodoke
Keyword(s):  
Electrical Resistivity ◽  
Electrical Resistivity Tomography ◽  
Geophysical Investigation ◽  
Resistivity Tomography ◽  
Entire Study ◽  
The North ◽  
Resistivity Method ◽  
Lateritic Clay ◽  
Edo State ◽  
Entire Study Area

Geophysical investigation using the 2D Electrical Resistivity Tomography (ERT) was carried out to assess the subsurface of Ugoneki and its environs in order to investigate for minerals. A total of six (6) traverses, 200 m long each, three (3) transverse lines were in the North-South direction and the other three (3) traverses in the West-East direction using the Wenner electrode configuration. 2D Wenner resistivity data were acquired along each traverse. The data were inverted to reveal a spatially continuous resistivity distribution in 2D within the study area. The 2D results reveal a depth of 39.6 m across each traverse. Resistivity values vary from 87.1 – 3423 Ωm in the entire study area. From the standard resistivity table, the following solid and non-metallic type of minerals can be delineated in the study area which is representative of sandy clay, lateritic clay sand, sandstone and limestone with resistivity values that range from 87.1 – 89.9 Ωm, 1201 – 1462 Ωm, 2069 – 3423 Ωm, and 2069 – 3423 Ωm respectively. The implication of this research is to know the type and the particular location where these non-metallic solid minerals are located in the subsurface for future exploration. The results of resistivity values are compared with those in the literature and are found to be in good agreement. In order to quantify these minerals, it is also recommended to use higher dimension (3D) of resistivity method (ERT) in the study area.

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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