Moreover, it can be used either in the form of vertical electrical soundings (VES's) or horizontal profiling to search for groundwater in both porous and fissured media (e.g., Barker, 1980; Van Overmeeren, 1989; Abd El-Rahman, A. and Khaled, M.A., 2005; and Abd Alla et al., 2005). for groundwater exploration around Nigerian College of Aviation Technology, Zaria Kaduna State, Nigeria. Sections below three ohm meters are likely brackish water—a mixture of freshwater and seawater that is unusable for human consumption or irrigation. However the interpretation of VES has been subjected to several indistinctness and efforts are on to tackle them. Since 1989, we’ve been producing state-of-the-art electrical resistivity meters and products for resistivity and induced polarization (IP) imaging. Field surveys were conducted with the Electrical Resistivity Imaging (ERI) technique, Electrokinetic System (EKS) sounding technique and Radon (222Rn) technique with the objectives of determining the best geophysical methods for borehole siting and its efficiency in the Volta Basin (VB) in the Northern Region of Ghana. Vertical Electrical Sounding To best understand how electrical resistivity surveys for groundwater exploration work today, it’s important to understand where resistivity testing began. EarthImager software makes this process easy; you can invert the apparent resistivity into true resistivity. cheaper. The isoresistivity contour map has been prepared based on the 45 VES conducted to determine the resistivity variations in the study area. Electrical Resistivity Method (ERM) is part of geophysical methods which used as preliminary step involve in any groundwater exploration. 1. Exploration and production of groundwater, a vital and precious resource, is a challenging task in hard rock, which exhibits inherent heterogeneity. The more saline, the more conductive the area will be. The result is an image that looks at a slice of the earth. ELECTRICAL RESISTIVITY and ELECTROMAGNETICsurveys are used to find fresh water and depth to groundwater. Electrical resistivity imaging is a widely used geophysical method for environmental site management studies. Brothers Conrad and Marcel Schlumberger performed the very first investigation of how electrical current moves through the ground and what you can detect using an electrical resistivity survey in the early 1900s. … The method allows a quantitative result to be obtained by using a controlled source of specific dimensions. To conduct a groundwater survey using AGI software and hardware, you would place a large number of electrode stakes at equal intervals. Fig. Electrical resistance survey of an archaeological site using a twin probe system In most systems, metal probes (electrodes) are inserted into the ground to obtain a reading of the local electrical resistance. (The electrodes are arranged in a straight line for a 2D survey and in a grid pattern for a 3D survey.) So why is it lower resistivity there? In Zimbabwe, the ERI was successfully used for groundwater exploration in Geoelectrical resistivity method involving vertical electrical sounding (VES) was carried out in a sedimentary environment to determine the suitability of the method for sub-surface groundwater investigations. The rainwater falling on the island percolates through the ground and out toward the sea. Brothers Conrad and Marcel Schlumberger performed the very first investigation of how electrical current moves through the ground and what you can detect using an electrical resistivity survey in the early 1900s. This is problematic for several reasons. Their study used schlumberger arrangement in fifteen (15) VES stations and the resultant data was analyzed using computer software (IPI2win) which gives an automatic interpretation of the apparent resistivity. The color scale shows the electrical resistivity of the ground. The Dc resistivity methods measure the electrical resistivity distribution of the subsurface using current transmitted into the ground from dc- or low-frequency sources, by two electrodes (C1 and C2), and measuring the potential difference between a second pair of electrodes (P1 and P2) (Fig. The interpretation of Schlumberger sounding data was first calibrated with the lithology of available nearby wells. Most soils and non-ore bearing rocks ar e electrically resistive, (i.e., insulators). To best understand how electrical resistivity surveys for groundwater exploration work today, it’s important to understand where resistivity testing began. Zimbabwe the use of resistivity surveys improved the success rate for wells from 50% to 85 % [2]. 2D Resistivity Survey for Groundwater Exploration in a Hard Rock Terrain: A Case Study of MAGDAS Observatory, UNILORIN, Nigeria Levi I. Nwankwo Abstract: A 2D electrical resistivity survey has been carried out for water exploration at the MAGDAS Observatory, University of Ilorin. The geophysical method which dominant by geophysicists become one of most popular method applied by engineers in civil engineering fields. Soil moisture and ground Electrical Resistivity. The resistivity is inversely proportional to the rock porosity and its water saturation. This repeats as the electrodes all move outward, further away from the centerpoint, which forces the current to take a deeper path. The changes in the electric resistivity values of geoelectrical section result from the material of the rock (density, shape, and porosity), water content, water quality and its content and temperature. From their research came what is now one of the most common methods of groundwater exploration, vertical electrical sounding (VES). A variety of probe configurations are used, most having four … Vertical Electrical Sounding (VES) is the most widely used geophysical techniques for groundwater prospecting. You would then connect them all to the SuperSting instrument using one cable with multiple take-outs. Sections betweenfive -and 100 ohm meters are likely freshwater. The Maghnia plain in western Algeria is filled by Plio-Quaternary and Miocene sediments that rest unconformably on a basement of Jurassic rocks. The two outer electrodes are used to inject an electric current into the ground—while the two inner electrodes measure the responding voltage. AGI’s SuperSting resistivity instrument and EarthImager inversion modeling software were created to make electrical resistivity imaging easier and more user-friendly and accurate for applications like groundwater exploration. ®‰íDè÷ÑÀ+>ºp´÷œ‚2ÿÖv-ülóCá4dHmihz\fCiŽdmñÈ_¹½Z ¡h­±{#(Ô÷å{£(p[3¨”ïübb&–ƒvz”áԅ¹4t GÉ5¬¼Ž. You can then use the voltage readings and injected current to detect changes in the resistivity of the ground below the center point. A geophysical survey was conducted in Méiganga, Mbéré department, in the Adamawa region, Cameroon. Submitted by markus on Mon, 11/14/2016 - 07:10. From their research came what is now one of the most common methods of groundwater exploration, vertical electrical sounding (VES). Electrical resistivity method is one of the most useful techniques in groundwater geophysical exploration, because the resistivity of rocks is sensitive to its ionic content (Alile, et al., 2011). of Electrical Resistivity. About 15% of these are Industrial Metal Detectors, 2% are Testing Equipment, and 0% are Other Electronic Measuring Instruments. • deep groundwater exploration (weathered bedrock, fault and dyke detection, groundwater table aquifers exploration) • deep mining exploration. Direct current resistivity method is a common tool for surveying water in arid areas. Advanced Geosciences Inc. (AGI) is the leading developer and manufacturer of geophysical imaging systems. The ERI technique has proven to be quite successful in groundwater exploration. As, the water content and its distribution change the electrical properties of the rocks. Kirsch [3] provides an overview of geophysical methods in support of groundwater exploration, and in that volume Rabbel [4] considers seismic and resistivity methods as second only to drilling for usefulness in determining the subsur-face structure. Applying geophysics for groundwater exploration and/or resource evaluation is only about 10 to 15 years in practice ... choice of the method(s), survey design, and data acquisition parameters. The recent study is managing geoelectrical resistivity field survey that was completed by applying VES method which measures the variation of the electrical resistivity with depth. Whether you’re examining groundwater subsidence or performing groundwater exploration, conducting a resistivity survey is an effective way to determine the best course of action. This raw data is called apparent resistivity; each data point can be seen as a weighted average of the resistivities in the area under the four electrodes that were used for this particular measurement. While knowing the apparent resistivity of a surveyed area is helpful, you’re likely more interested in knowing the resistivity at a specific point in the subsurface. Consider a nongovernmental organization (NGO) that wants to help a small community drill a well. The EC and TDS hydrochemical data in the study area clearly showed the influence of seawater intrusion. It is well known that this method can be successfully employed for ground water investigations, where a good electrical resistivity contrast exists between the saturated and unsaturated layers. Four geoelectrical layers were identified within the study area. The three main methods of electric resistivity surveys are vertical electric sounding (VES), electric profiling, and electric imaging. Without going into the physics of Ohm’s law, if you run a current through different materials you can calculate the electrical resistance by measuring the voltage and current applied. Applicable alternative technique in groundwater exploration such as ERM which complement with existing conventional method may produce comprehensive and convincing output thus effective in terms of cost, time, data coverage and … Electrical Resistivity Method (ERM) is one of geophysical tool that offer very attractive technique for subsurface profile characterization in larger area. They conduct an electrical resistivity survey and see that there are large pockets of resistivity that are likely water—but they want to tap only into the freshwater lens without tapping into salt water. If you conduct your electrical resistivity survey using an AGI imaging system, our staff will be there to help you from start to finish with free technical support. Alibaba.com offers 1,010 resistivity meters for ground water exploration products. VES has been used for groundwater exploration for decades—but (1) you have to move at least two electrodes (and sometimes all four) for every measurement and (2) it only works if the ground is horizontally layered and each layer is homogeneous. They are a thin n… 3a, b, c and d). for groundwater exploration in fractured reservoirs Muhammad Taqiuddin Zakaria, Nordiana Mohd Muztaza*, Adeeko Tajudeen Olugbenga, ... the depth of investigation for 2-D resistivity surveys. Sections at or below 0.25 ohm meters are likelyseawater or brine water (which is hypersaline water)—both are unusable for human consumption and irrigation. Tarkwa. The resistivity of the fracture will be lower than that of hard rock, because in hard rock the moisture will collect in the fissures of the fracture zone—the blue in the fracture is lower than the green in the hard rock surrounding the fracture. The freshwater forms an underground freshwater lens that floats on top of the heavier salt water. This happens automatically many times in different electrode configurations according to a pre-programmed pattern until a large amount of data is collected. Each of these utilize one of the array configurations mentioned above. Freshwater doesn’t transmit electric current well, making it easy to identify. This is a big improvement over the vertical electrical sounding (VES) method, as it’s quicker, easier to conduct, and much more accurate. Electrical resistivity tomography (ERT) is a popular geophysical subsurface-imaging technique and widely applied to mineral prospecting, hydrological exploration, environmental investigation and civil engineering, as well as archaeological mapping. By inverting the data on the EarthImager software, they’re able to gather the following: This saves the NGO from drilling into pockets of seawater, brine water, or brackish water—which could be a costly and time-consuming mistake. ERM has been applied for many years to determine the thickness of layered media as well to map geological environment of existing aquifer. Keywords: groundwater, electrical resistivity, geological and geophysical properties INTRODUCTION Groundwater is the water that lies beneath the ground surface, filling the pore space between grains in bodies of sedimentary rock, filling cracks and crevices in all types of rock (Plummer et al., 1999). The electrical resistivity technique is a preferable geophysical technique for groundwater exploration. Fresh groundwater is a scarce commodity on small islands at sea, as it is only recharged  during rainfall. Also, the ground is very rarely layered perfectly—there are usually geologic anomalies above or below the surface that will make VES difficult or inaccurate. Even though the 4-electrode electrical resistivity system and the ERI depend on the same basic principles, the ERI has proven to be more efficient (Ewusi et al., 2009). When the survey begins, the electric current is injected between two electrodes, and the response is measured between two other electrodes. For example, if you were imaging a sand and gravel bed for groundwater exploration purposes, you’d likely want to see a color-coded image where the sand and gravel bed is outlined with a specific color representing each resistivity. Surface electrical resistivity surveying is based on the principle that the distribution of electrical potential in the ground around a current-carrying electrode depends on the electrical resistivities and distribution of the surrounding soils and rocks. Distances between the outer electrodes can reach up to 1,000 meters—so either one person will be doing a great deal of walking, or more people are needed for the survey. Further, electrical resistivity surveys were conducted to determine the subsurface lithology and also to confirm the studies of LANDSAT imagery. Although several methods are available for the purpose, two methods viz., the electrical resistivity and seismic refraction methods have been successfully used for groundwater investigation. Electrical sounding (VES), magnetic data, well information, and hydrogeological data have been used to explore for groundwater potential in the Maghnia plain. VES uses four electrodes placed in line around a defined center point. First, moving two (or more) electrodes for every measurement is extremely time consuming and could take up more man power. fact that, the electrical resistivity survey is one of the simplest and less costly geophysical surveys employed. VES is one of the more commonly used … These methods have been originally developed for petroleum and mineral exploration. ELECTRICAL RESISTIVITY SURVEYS Electrical resistivity is a geophysical method in which an electrical current is injected into the ground through steel electrodes in an attempt to measure the electrical properties of the subsurface. A wide variety of resistivity meters for ground water exploration … VES … In practice this means that a resistivity survey will form an electrical circuit through the ground and take voltage and current measurements to calculate the resistivity of the sub-surface rocks. Electrical Resistivity Method (ERM) is … NUCLEAR MAGNETIC RESONANCEis used when information on formation porosity and bore yield is critical. I Fullwaver The I Fullwaver systems were specifically developed for precise full waveform time domain induced polarisation, resistivity … Only the principles of these methods will be given here. Vertical Electric Sounding. Process easy ; you can invert the apparent resistivity into true resistivity bearing rocks ar e resistive... 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