Combined application of dc and TEM to sea‐water intrusion mapping

Geophysics ◽  
1999 ◽  
Vol 64 (2) ◽  
pp. 417-425 ◽  
Author(s):  
Chieh-Hou Yang ◽  
Lun-Tao Tong ◽  
Ching-Feng Huang
Keyword(s):  
Pore Water ◽  
Sea Water ◽  
Salt Water ◽  
Joint Inversion ◽  
Empirical Relation ◽  
Dc Resistivity ◽  
Water Conductivity ◽  
Archie’S Law ◽  
Resistivity Method ◽  
Transient Electromagnetic

A geoelectric survey using a dc resistivity method and a transient electromagnetic induction (TEM) method was carried out from 1986 to 1988. It was used to help map the lateral and vertical distributions of the freshwater/salt‐water interface in the Pei‐kang area on the west coast of Taiwan. The dc and TEM soundings were performed at 79 localities over an area of 240 km2 of Quaternary alluvium. Significant changes in pore‐water conductivity at some places were detected by these two methods. A low resistivity value (<1.5 ohm-m) implies salt‐water contamination of groundwater. The results of spatial distribution of apparent resistivity indicate the salt‐water‐affected aquifers are confined to the southwest part of the study area, and the affected aquifers are confined to the top of two aquifers. A geoelectric model with three to four layers is inferred from the joint inversion of dc and TEM data. Based on a modified Archie’s law suggested by the authors, an empirical relation between pore‐water resistivity of the stratum and formation resistivity can be obtained. It can be used to convert the computed resistivity of each geoelectric layer (aquifer) to the resistivity of the water contained in these layer, thus leading to the assessment of groundwater contamination. Repeated dc resistivity measurements have been carried out at selected locations once every year from 1986 to 1988. These data were used to monitor the temporal variation and a possible spreading of the salt‐water invasion. During 1995, a dc survey was conducted in the same area to compare with the dc sounding results obtained in 1988. The final results provide an evaluation of the efficiency of groundwater management in the study area.

scholarly journals PEMETAAN STRUKTUR SITUS COT SIDI ABDULLAH PENINGGALAN KERAJAAN SAMUDERA PASAI BERDASARKAN SEBARAN MODEL RESISTIVITAS

2020 ◽  
Vol 12 (02) ◽  
pp. 115
Author(s):  
Agus Hari Pramana ◽  
Faisal Abdullah ◽  
Tomi Afrizal ◽  
Nazli Ismail
Keyword(s):  
Sea Water ◽  
Middle Part ◽  
Electrode Spacing ◽  
Dc Resistivity ◽  
Brick Wall ◽  
Model Resolution ◽  
Resistivity Method ◽  
Wall Structures ◽  
Method Model ◽  
Sand Material

Metode DC-Resistivity konfigurasi Wenner telah diaplikasikan pada situs cagar budaya Cot Sidi Abdullah (CSA) di Desa Kuta Krueng, Kecamatan Samudra Pasai, Kabupaten Aceh Utara. Data geolistrik diukur pada 8 lintasan sejajar dengan spasi lintasan 5 meter dari arah utara - selatan sepanjang situs dan spasi elektroda 0,5 meter. Berdasarkan hasil model penampang 2D diperoleh zona yang bersifat konduktif dengan kisaran nilai resistivitas 0,1 – 80 Ωm dan zona resistif dengan nilai reistivitas berkisar antara 100 – 600 Ωm dengan ketebalan lapisan 1 meter. Keberadaan zona yang relatif konduktif disebabkan oleh adanya intrusi air asin yang terdapat disekeliling daerah itu, yaitu area tambak dan sungai. Sedangkan zona resistif terdapat secara merata di semua lintasan yang umumnya berada di tengah–tengah lintasan dan dapat diprediksikan sebagai bagian dari situs yang tertimbun dibawah permukaan. Zona resistif berupa batu bata yang berada di sekeliling situs dan menahan intrusi air asin masuk ke tengah. Oleh karena itu bangunan Situs CSA diprediksi memiliki luasan sekitar 26 m x 35 m dengan bangunan sekeliling berupa batu bata dengan ketebalan dinding situs 1,5 meter. Sedangkan bagian tengah adalah timbunan pasir yang tidak dipengaruhi oleh air asin.Kata kunci: Metode geofisika, Arkeologi, Cot Sidi Abdullah, Metode DC - Resistivity, Resolusi Model, RekontruksiThe DC-Resistivity method with Wenner configurations was applied to the cultural heritages of Cot Sidi Abdullah (CSA) in Kuta Krueng Village, Samudra Pasai District, North Aceh Regency. Resistivity data were measured on 8 parallel lines with 5 meterline spacing from north to south of the sites and 0.5 meter electrode spacing. The 2D model results show that there are conductive region with the value of resistivity from 0.1-80 Ωm and resistive region with resistivity values ranging from 100 - 600 with a thickness of 1 meter. The existence of the relatively conductive region is caused by the sea water intrusions which is found surrounding the area, such as fish and river areas. However the resistive region is evenly found in all of the lines which are generally located in the middle of line and it was predicted as a part of Cot Sidi Abdullah site buried under the surface. The resistive region is consist of brick wall structures which surrounding the site can hold the sea water intrusions into the center of the sites. Therefore it can be concluded that the CSA Site has 26 m x 35 m areas which is surrounded by the brick structures with 1.5 meters thick. Howeverthe middle part of the site is filled with a sand material that is not affected by salt water.Key words: Geophysics Method, Archaeology, Cot Sidi Abdullah, DC- Resistivity Method, Model Resolution, Reconstruction

scholarly journals GEO-ELECTRICAL MAPPING OF BEACHROCK IN VATERA BEACH, LESVOS

2017 ◽  
Vol 50 (4) ◽  
pp. 2323
Author(s):  
R. Meligonitis ◽  
D. Galanopoulos ◽  
T. Hasiotis ◽  
A. Velegrakis
Keyword(s):  
Sea Water ◽  
Electrode Array ◽  
Coastal Environment ◽  
Dc Resistivity ◽  
Coastal Zones ◽  
Geoelectric Model ◽  
Resistivity Method ◽  
Specific Host ◽  
Electrical Resistivity Method ◽  
Morphodynamic Evolution

Beachrock (Br) is encountered on the coastal zones, playing an important but also complex role in their morphodynamic evolution. Although Br has been widely studied, two important issues require further investigation. The first concerns the importance of the interaction of the dynamically changing coastal environment with the temporal changing surficial and underground hydrogeological balance. The second has to do with the spatial distribution and the evolution of Br with respect to the specific “host” coastal zone geo environment. This paper designates the electrical resistivity method as a tool that contribute in arguing in the abovementioned issues. The research comprised subsurface measurements with the DC resistivity method along two profiles located on Vatera beach (Lesvos Island), where there is a significant Br outcrops. Twelve geoelectric soundings were carried out using the Axial Pole-Dipole electrode array. The electrical resistively measurements permitted an indirect estimation of TDS, which depicts the coastal interface of fresh water - sea water. The interpreted geoelectric model shows two thin formations attributed to Br. The first is the inland extension of the Br outcrop and the second it is believed to be a primary stage of Br build up.

Improvement in MRS parameter estimation by joint and laterally constrained inversion of MRS and TEM data

Geophysics ◽  
2012 ◽  
Vol 77 (4) ◽  
pp. WB191-WB200 ◽  
Author(s):  
Ahmad A. Behroozmand ◽  
Esben Auken ◽  
Gianluca Fiandaca ◽  
Anders Vest Christiansen
Keyword(s):  
Water Content ◽  
Joint Inversion ◽  
Synthetic Data ◽  
Clear Correlation ◽  
Model Parameters ◽  
Dc Resistivity ◽  
Borehole Data ◽  
Simultaneous Inversion ◽  
Transient Electromagnetic ◽  
Magnetic Resonance Sounding

We developed a new scheme for joint and laterally constrained inversion (LCI) of magnetic resonance sounding (MRS) data and transient electromagnetic (TEM) data, which greatly improves the estimation of the MRS model parameters. During the last few decades, electrical and electromagnetic methods have been widely used for groundwater investigation, but they suffer from some inherent limitations; for example, equivalent layer sequences. Furthermore, the water content information is only empirically correlated to resistivity of the formation. MRS is a noninvasive geophysical technique that directly quantifies the water content distribution from surface measurements. The resistivity information of the subsurface is obtained from a complementary geophysical method such as TEM or DC resistivity methods. The conventional inversion of MRS data assumes the resulting resistivity structure to be correct and considers a constant MRS kernel through the inversion. We found that this assumption may introduce an error to the forward modeling and consequently could result in erroneous parameter estimations in the inversion process. We investigated the advantage of TEM for the joint inversion compared to DC resistivity. A fast and numerically efficient MRS forward routine made it possible to invert the MRS and TEM data sets simultaneously along profiles. Furthermore, by application of lateral constraints on the model parameters, lateral smooth 2D model sections could be be obtained. The simultaneous inversion for resistivity and MRS parameters led to a more reliable and robust estimation of all parameters, and the MRS data diminished the range of equivalent resistivity models. We examined the approach through synthetic data and a field example in Denmark where good agreement with borehole data was demonstrated with clear correlation between the relaxation time [Formula: see text] and the grain size distribution of a sandy aquifer.

Investigational Studies on Quantity of Salinity in Netravati River Estuary Sand-Coastal Karnataka

2018 ◽  
Vol 6 (6) ◽  
pp. 46
Author(s):  
Raveesha P ◽  
K. E. Prakash ◽  
B. T. Suresh Babu
Keyword(s):  
Brackish Water ◽  
Sea Water ◽  
Salt Water ◽  
Construction Material ◽  
Salt Content ◽  
River Estuary ◽  
Sand Sample ◽  
River Sand ◽  
Natural Aggregates

The salt water mixes with fresh water and forms brackish water. The brackish water contains some quantity of salt, but not equal to sea water. Salinity determines the geographic distribution of the number of marshes found in estuary. Hence salinity is a very important environmental factor in estuary system. Sand is one major natural aggregate, required in construction industry mainly for the manufacture of concrete. The availability of good river sand is reduced due to salinity. The quality of sand available from estuarine regions is adversely affected due to this reason. It is the responsibility of engineers to check the quality of sand and its strength parameters before using it for any construction purpose. Presence of salt content in natural aggregates or manufactured aggregates is the cause for corrosion in steel. In this study the amount of salinity present in estuary sand was determined. Three different methods were used to determine the salinity in different seasonal variations. The sand sample collected nearer to the sea was found to be high in salinity in all methods.  It can be concluded that care should be taken before we use estuary sand as a construction material due to the presence of salinity.

Evaluation of Heavy Metal Contents in Mudflat Solar Salt, Salt Water, and Sea Water in the Nationwide Salt Pan

2012 ◽  
Vol 41 (7) ◽  
pp. 1014-1019 ◽  
Author(s):  
Hag-Lyeol Kim ◽  
Young-Joo Yoo ◽  
In-Sun Lee ◽  
Gang-Hee Ko ◽  
In-Cheol Kim
Keyword(s):  
Heavy Metal ◽  
Sea Water ◽  
Salt Water ◽  
Solar Salt ◽  
Metal Contents ◽  
Salt Pan

Studies on Salt and Water Balance in Caddis Larvae (Trichoptera)

1961 ◽  
Vol 38 (3) ◽  
pp. 521-530 ◽  
Author(s):  
D. W. SUTCLIFFE
Keyword(s):  
Sea Water ◽  
Salt Water ◽  
Chloride Concentration ◽  
Malpighian Tubule ◽  
Sodium Concentration ◽  
Fluid Composition ◽  
Chloride Level ◽  
Highly Sensitive ◽  
Water Media ◽  
Salt And Water Balance

1. Survival and regulation in sea-water media was studied in the freshwater caddises Limnephilus stigma and Anabolia nervosa. 2. The majority of larvae did not survive for more than a few days at external salt concentrations greater than about 6o mM./l. NaCl. 3. In sea-water media the haemolymph osmotic pressure increased to remain slightly hyper-osmotic to the medium. The haemolymph sodium level also increased to remain slightly hypertonic to the medium, but the chloride level was maintained hypotonic until just prior to death of the larvae. 4. When the haemolymph chloride concentration was raised above the normal level, the Malpighian tubule-rectal system elaborated fluid in which the chloride concentration was hypertonic to the haemolymph. The system is highly sensitive to changes in the haemolymph chloride level. 5. The regulation of body-fluid composition in the freshwater caddises is compared with that found previously in the euryhaline larvae of Limnephilus affinis. It is suggested that the maintenance of a low haemolymph sodium concentration in L. affinis larvae is an important part of the adaptation for survival in salt water.

Sea Water Intrusion Monitoring on the Sendangbiru of the Southern Malang Coastal Area based on Geoelectrical Resistivity Data

2021 ◽  
Vol 14 (9) ◽  
pp. 43-48
Author(s):  
Sunaryo .
Keyword(s):  
Data Acquisition ◽  
Cross Section ◽  
Seawater Intrusion ◽  
Cross Sections ◽  
Sea Water ◽  
Salt Water ◽  
Sea Water Intrusion ◽  
Electrical Sounding ◽  
Geoelectrical Resistivity ◽  
Intrusion Layer

The study was conducted with the objective to distinguish the presence of seawater intrusion layer or salt-water aquifer distribution along the data acquisition line at the locations. Data acquisition was conducted by using the Wenner-Schumberger configuration of geoelectrical resistivity. From this research, 4 lines and 4 points of vertical electrical sounding (VES) data for every line were obtained with the distance between electrode a as 10m. Based on the data processing, obtained depth up to 120m with the smallest resistivity value is 0.02Ωm and the largest is 6764.52Ωm. To make the distribution of resistivity values along the path line of the study, cross sections were made until a depth of 120m. Based on the cross-section, the low resistivity value (less than 1.5 Ωm) that interpreted as a seawater intrusion layer or salt water aquifer distribution is located at varying depths. There are intrusions for the SB1 cross section, there is an intrusion at a depth of 6m-7m as far as 10m, at a depth of 6m-8m as far as 10m for the SB2 cross section and at a depth of 22m - 26m as far as 25m for the SB3 cross section.

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