Posted at 10.09.2018
The role of geophysical methods in Groundwater Exploration is essential. Its chief goal is to comprehend the invisible subsurface hydrogeological environment appropriately and effectively. As the base of any geophysical methods is the compare between your physical properties like the features, items, and layers and the surroundings.
Parker et al, (2009) mentioned that object are just established when the compare is sufficiently large enough to change the geophysical sign depicting the anomaly as an 'alien' feature of the subsurface i. e. , different physical and/or chemical properties than the environment where it is located. They also mentioned that geophysical method will not only characterise the subsurface but also place inhomogeneous features or aim for that aren't characteristics of the encompassing 'sponsor' material in normal water, water-covered, earth or sediments. Thus the better the contrast or anomaly, the better would be geophysical response and therefore the recognition. So, the efficiency of any geophysical techniques is based on its potential to sense and deal with the concealed subsurface hydrogeological heterogeneities or disparity.
For groundwater exploration a cautious appliance or combination of techniques is most vital to be successful in exploration, technologically as well as cost-effectively. It really is undeniably conceptualized that groundwater cannot be detected immediately by any one of the geophysical methods and then the interpretation is appropriate and a broad knowledge of the subsurface hydrogeological condition or setting is crucial. Hubbard S. S et al. , (2000), Ugur Yaramanci et al. , (2002) and Ramke L. Vehicle Dam (2010) stresses the utilization of several complementary geophysical methods to improve data interpretation. With multiple collocations of geophysical data available, excellent results will be produced with significantly better interpretations than when with an individual method.
Conventional geophysical methods have often been used to map the geometry of aquifers such as seismic, electro-mechanical and electromagnetic methods (Wattanasen et al (2008)). These methods have been used to identified and estimate locations, transmission properties, safe-keeping and the aquifer materials regardless of the ambiguity of the interpreted results due to restriction in each method and the site dependence. But with the improvements in instruments, the development of better methods as led to a widening of its applications.
The primary purpose of resistivity method is to look for the subsurface resistivity distributions by making measurements on the ground surface. There by calculating the actual difference on the surface because of the current movement within the ground. From this way of measuring the true resistivity of the subsurface can be estimated. The mechanism in charge of the fluid flow and electric energy and conduction in porous advertising corresponding to P. M Soupious et al. , 2007, are generally governed by the same physical variables and lithological features, thus the hydraulic and electric conductivities are dependents on one another, while H. S. Salem et al. , 1999, indicated that electric-current conduction is influenced by various mechanisms in a saturated systems and can be represented by the two-phase model (grain-matrix conductance) known as dispersed phase, and pore-fluid conductance also called continuous stage. The two-phase model can further be progressed into a five-phase model, comprising surface conductance happening at the billed fluid-solid user interface, ion-exchange conductance, Maxwellian-effects conductance of both solids in the matrix and those suspended in the pore liquid, grain-matrix conductance and pore smooth conductance.
The electronic conduction in the subsurface is principally electrolytic because most minerals grains are insulators, therefore, the conduction of electricity is through the interstitial normal water/ or fluids in the skin pores and fissures. These pore space and fissure of stones are crammed by groundwater which is a natural electrolyte. The factors accountable for the move and conduction of electro-mechanical resistivity in earth and rocks are really variable and can vary by several purchases of magnitude. These factors matching to Loke, 1999 are porosity, amount of drinking water saturation and amount of dissolved solids, O. A. L. de Lima et al. , 2000; tortuosity and porosity, P. M Soupious et al. , 2007; lithology, mineralogy, size, shape, packing and orientation of mineral grains, condition and geometry of skin pores and pore stations, permeability, compaction, magnitude of porosity, consolidation and cementation and depth and drinking water distribution.
The resistivity of sedimentary stones, which can be usually more porous, with high drinking water content is highly variable with low resistivity and depends upon its formation factor. Formation factor is a very powerful tool in resistivity surveys as it allows pore fluid resistivity to be computed directly from mass earth resistivity measurements. This romantic relationship can even be used to convert earth resistivity contours in to smooth conductivity or TDS curves.
Bulk resistivity of the ground is assessed from direct current resistivity and it obeys an empirical legislation within an aquifer. This was first suggested by Archie (1942) and the partnership may be expressed as: = a - m S- n f
Where is the porosity of the rock development, S is the amount of saturation, a, m, and n are constants that depend after the creation, f is the resistivity of pore substance. Archie's Law demonstrates bulk resistivity of totally saturated formation of any granular medium formulated with no clay depends significantly on the resistivity of the pore smooth f. That is mainly consequently of the resistivity of the fluid much lower than that of the sturdy grains in the matrix. Given that, 'matrix conduction' is negligible and the electric current passes almost entirely through the smooth phase, thus making resistivity methods a lot more very important to hydrological studies. (S. R Wilson et al. , 2006). Archie's regulation can thus be expressed as:
= a - m f,
assuming that at saturation, S is1.
where is the majority resistivity, f is the smooth resistivity, is the porosity of the medium, m is recognized as the cementation factor and a, the tortuosity factor, cementation intercept, lithology factor or lithology coefficients is associated with the medium and its own value oftentimes departs from the commonly assumed value of one. It is meant to correct for variation in compaction, pore composition and grain size.
According to H. S. Salem 1999, the cementation factor of Archie;s equation has specific effects on electric conduction techniques in porous multimedia and exhibits intensive disparities from sample to sample, development to formation, interval to interval in the same medium and from medium to medium. Due to its reliance on various properties, m has been known as cementation factor, shape factor, conductivity factor, porosity exponent, resistivity factor, and cementation exponent. The dependence of m on the amount of cementation is not as strong as its dependence on the grain and pore properties (condition and type of grains, and form and size of pores and pore throats). It is therefore more appropriate to spell it out m as condition factor rather than cementation factor.
Resstivity survey has been used for several geological purposes. S. Srinivas Gowd, 2004, J. O. Oseji, 2006, A. G. Batte et al. , 2010, used surface electric resistivity research to delineate groundwater potentials, A. Samouelian et al. , 2005, used electric powered resistivity survey in land, S. R. Wilson et al. , for saline user interface explanation, M. Arshad et al. , 2006, for lithology and groundwater quality willpower, A. Turesson, 2006, for water content and porosity estimations.
S. R Wilson, et al, (2006) applied globe resistivity methods in determining saline user interface in Te Horo on the Kapiti Coast in New Zealand. They used vertical electric sounding (VES) and immediate current resistivity traversing which includes been usually successful in defining subsurface regions of higher salinity by giving a two-dimensional image of the bulk resistivity framework.
A VES strategy has been used most regularly to find the scope of saline interface using the Schlumberger array geometry. It shows deviation in large resistivity with distance from the coast which could be related to the amount of saline blending but fails to surrender depth picture of both location or structure of the saline user interface. However, with the location of the estimated saline interface known, resistivity traversing can be used to improve its location and form.
They result obviously show the probable of resistivity traversing in mapping and in understanding the structure and development of saline user interface in coastal aquifers. Even though VES data may resolve one-dimensional resistivity framework beneath a sounding location, any two- dimensional interpretation of the info requires interpolation between discrete measurements. On the other hand, resistivity traversing data provide ongoing two-dimensional image of both lateral and vertical variants in resistivity. Quite contrast in the electro-mechanical resistivity of saline and fresh water allows direct imaging of any sharp saline interface.
However, they used formation factor to interpret resistivity data from a much wider area. The creation factor for an aquifer is identified from Archie's Legislations with an assumption that at saturation S is 1, as
Sharma et al (2005), carried out an integrated electric powered and very low rate of recurrence (VLF) electromagnetic studies to delineate groundwater- bearing areas in hard rock and roll areas of Purulia districts, west Bangal, in India for the building of profound tube-wells for huge amounts of water.
The location of potential fractures areas in hard rock and roll areas to yield large amounts of groundwater is very hard and therefore cannot be easily done using one strategy. Hence groundwater probable of any location in hard rock and roll areas requires several techniques, geophysical as well as hydrogeological techniques to increase groundwater produce.
Electrical and electromagnetic geophysical methods have been thoroughly found in the search for groundwater because of this of good relationship between electrical power properties, smooth content and geology. Groundwater in hard rock and roll areas is generally found in cracks and fractures and therefore the yield depends upon the interconnectivity and size of the fractures.
The merged use of DC resistivity soundings, SP dimension, Wenner profiling and VLF electromagnetic were used to map the fractures in hard rock areas. VES method was used to identified resistivity variations with depth but can't be performed everywhere you go without the priori information. The VLF was successful in mapping resistivity distinction in boundaries of fractures with high levels of connectivity and also as a result of these high resistivity they are proved to produce a higher depth of penetration in hard rock areas. Also, VLF data pays to in determining suited strike direction to perform resistivity sounding i. e. parallel to reach and thus enhancing the probability of success. Resistivity profiling and SP way of measuring also give important information about the presence of the conductivity fracture and groundwater activity.
They figured VLF dimension only give indications of the existence of conductive area but cannot differentiate between profound and shallow sources. Hence, it is vital to follow the positioning of the VLF anomalies with a technique that investigate the depth of the conductive sources. Therefore, the Schlumberger sounding strategy was became effective in determining resistivity variance with depth.
A review on the utilization of electrical resistivity study as put on soil was completed by Samoulian et al, (2005) to re-examine the basic concept of the technique and the several types of arrays devices used (one-, two- and three-dimensional arrays), the sensitivity of electronic measurements to ground properties which includes the degree of drinking water saturation i. e. water content, design of voids such as porosity and pore size syndication connectivity and the type of the sound constituents such as particle size syndication and mineralogy and the key advantages and restrictions of the technique.
They review indicated that electric powered resistivity is non-destructive and can provide continuous measurements over a large range of areas when compared with the conventional dirt science measurements and observation which disturb the land by random and or regular drilling and sampling. Due to these temporal variables such as water and seed nutriment, depending on internal framework can be monitored and quantified without changing the garden soil structure. Thus the application is numerous which include; determination of land horizonation and specific heterogeneities, follow-up of the transfer phenomena and the monitoring of solute plume contamination in a saline or waste products context. However, they advised that electric measurements do not give straight access to land characteristics that is of interest to the agronomist and therefore preliminary lab calibration and qualitative or quantitative data interpretations must be carried out in order to connect the electro-mechanical measurements with the garden soil characteristics and function.
Direct and indirect method of groundwater inspection was carried out in southern Sweden using magnetic resonance sounding (MRS) and vertical electronic sounding (VES) by Wattanasen et al, (2008). The purpose of the study was to compare MRS with VES and other geophysical methods. The MRS results were regular with VES. It really is a successful tool in groundwater exploration particularly in an area of sedimentary stones of high magnitude of globe magnetic field. An excellent quality data was obtained because of this of low ambience sound, low deviation in the planet earth magnetic field and advanced of MRS sign. The MRS was effective in determining the depth to normal water layers, water content and their thickness. It can also detect normal water in areas with high conductive clay covering that is near the surface, a factor that restricts the penetration depth of other geophysical methods like GPR.
Hydraulic properties are essential variables in hydrogeology for accurate modelling of groundwater movement and rate of activity of contaminant or pollution. These properties; hydraulic conductivity, transmissivity and storage space coefficient are used to spell it out and quantify the capacity of the materials composing aquifers and confining systems to transmit and store normal water. The hydraulic conductivity and storage space coefficients (storativity) are aquifer properties that may vary spatially because of geologic heterogeneity.
Traditionally, pumping test or laboratory techniques when key samples can be found have been used to determine the aquifer hydraulic parameters. These methods have been proved to be intrusive and expensive and offer information only near the boreholes and the test locations. The application of geophysical techniques could be observed as a way of providing important complementary information that may help to reduce the costs of hydrogeological investigations.
Aristodemou et al. , (1999) and Soupious et al. , (2007) also applied surface geophysical ways to determine the hydraulic conductivity worth using both Kozeny-Carman-Bear equation and the Worthington equation.
According to Worthington equation: Fa=Fi. (1 + BQvw)- 1 (1)
where, Fa is the obvious formation factor, Fi is the intrinsic formation factor and the BQv term is related to the effects of surface conductance, mainly due to clay particles. In case surface conductance results are non-existent, the noticeable formation factor becomes add up to the intrinsic one. Thus, 1/Fa= 1/Fi +( BQv/Fi)w (2)
Where 1/Fa, is the intercept of the right range and BQv/Fi presents gradient. Thus, by plotting 1/Fa versus liquid resistivity w, we have to in principle, obtain a value for the intrinsic creation factor, which will subsequently enable us to calculate porosity from the formula
o = a w - m where o is the bulk resistivity, w is the substance resistivity, is the porosity of the medium and m is the cementation factor, although it is also interpreted as grain-shape or pore-shape factor; the coefficient of an is associated with the medium and its value in many cases departs from the commonly assumed value of 1.
The apparent creation factor Fa =o/w, where o is the majority resistivity obtained from the resistivity inversion and w is the fluid electrical resistivity extracted from the borehole.
These porosities were subsequently used to calculate the hydraulic conductivity through the Kozeny-Carman-Bear equation.
K = ( ґwg / ј). (d2 /180). [ (3 / (1 - 2 ) ]
Where d is the grain size, ґw is the fluid density, and ј is the powerful viscosity.
Andreas Hordt et al. , (2006) and Andrew Binley et al. , (2005) used spectra induced polarization to determine the hydraulic conductivity. There work was focussed on lab experiments to be able to establish a semi- empirical romantic relationship between complex electric resistivity and hydraulic variables and then applied the field technique to evaluate the feasibility of the technique.
Thus the hydraulic conductivity, k was then determined from the Kozeny- Carman formula based on creation factor and interior surface.
K = 1/ F(Spor)c,
The exponent c can be an variable parameter.
Complex electronic conductivity was used as a convenient means of hydrogeological applications;
Ж = " Ж"ei = Ж' + iЖ''
Where Ж' and Ж'' denote real and imaginary part, and "Ж" and denote magnitude and period, of the conductivity Ж.
Formation factor was computed from the formula:
F = Ж w/ Re(Ж) - Im (Ж)/l
where Жw is the pore liquid conductivity. The factor l is the percentage between imaginary and real part of the surface conductivity.
The pore space- internal surface area, Spor can be an empirically derived formula from laboratory.
Anita Turesson (2006), applied surface- penetrating radar and resistivity independently to evaluate their capacity to assess water content and porosity for saturated area in a sandy section, since dielectric and the resistivity of stones and sediments are very much reliant on moisture content. Archie's empirical formula was used in the resistivity solution to determine the partnership between resistivity and porosity (Andrew Binley et al. , 2005) in the sedimentary clay free stones predicated on the creation factor, which is the percentage of resistivity of the porous mass media compared to that of the pore fluid. The results obtained shows good contract between your two methods in the saturated zone plus they use of the independent methods greatly strengthen the results.
Another subsurface geophysical techniques is the Induced Polarization (IP) technique which within the last years has been used effectively for mineral exploration by giving in situ information about rock and roll mineralogy mainly disseminated ores and mineral discrimination. Recently the method has been applied in the field of environment and executive studies to materials which do not contain conductive minerals but instead clay nutrients for the mapping of polluted land areas, movement of impurities and grain size distribution variables in unconsolidated sediments (E. Aristodemou et al. , (2000); Andreas Hordt et al. , 2006, 2007)).
In theory, induced polarization is a dimensionless number whereas in practice it is assessed as a change in voltage as time passes or frequency. The time and occurrence IP methods are fundamentally similar, however, they are different in a way of considering and measuring electrical waveforms. In the former, a direct current is applied in to the ground, and what's registered is the decay of voltage between two potential electrodes following the cut off of the existing (time-domain method). Inside the latter, the variant of visible resistivity of the ground with the frequency of the applied current is set (frequency-domain method). In a different type of frequency method, to create Complex Resistivity (CR) method, a current at regularity range (0. 001 Hz to 10 kHz) is injected in the bottom and the amplitude of voltage as well as its stage with respect to the current is assessed. That is clearly a phase-angle IP dimension.
Various studies have been carried out most recently to establish an empirical romantic relationship between hydraulic properties and induced polarisation measurements, though only limited variety of studies exists so far at a field range. The reason for this is the fact hydraulic properties depend on both porosity and geometry of the pore space.
Induced polarisation (IP), is the only real geophysical methods that is determined by surface characterisation and has been used in hydrology as the possible link to hydraulic properties. (Binley et al. , (2005)).
Semi-emperical interactions between IP and hydraulic properties have been thoroughly investigated. Andreas Hordt et al. , (2007), projected hydraulic conductivity from induced polarisation using multi-channel surface IP dimension over a fine sand/gravel aquifer at Krauthausen. Despite undertaking measurement over a wide rate of recurrence range called spectra IP, the hydraulic conductivity examination was limited to single occurrence data based on the Borner model and Slater and Lesme model. They however, used two different approaches to determine the hydraulic conductivities from the IP results. The first methodology is the B¶rner method refered to as the constant-phase perspective (CPA), where real and imaginary parts of complex electronic conductivity was sufficient to estimate the hydraulic conductivity from the Kozeny-Carman type equation; k=1/F(Spor)c, based on two parameters; the development factor and the pore-space related interior surface, Spor which was empirically produced from lab measurements.
The second approach suggested by Slater and Lesme was predicated on an empirical romance between k and the imaginary part of conductivity at 1 Hz without needing the true part and/or the development factor:
K=m/(b")n. This is predicated on the argument that hydraulic conductivity mostly depends on the specific interior surface.
Andrew Binley et al. 2005, worked on the relationship between spectra induced polarisation and hydraulic properties of saturated and unsaturated sandstone. They attempted to see the spectra IP response of examples taken from the united kingdom sandstone aquifer and likened the measured parameters with the physical and hydraulic properties. There effect shows that the mean relaxation time, †, is a more suitable way of measuring IP response for these sediments, with a significant inverse correlation existing between the surface to pore volume level ratio and the †, suggesting that † is a way of measuring a quality hydraulic length level. This was supported by a solid positive relationship between log K and log †. There results exposed significant impact of saturation on the measured spectra, thus limiting the applicability of hydraulic-electric models in using the SIP measurements. However, on the other hand, they suggested new opportunities for development of in physical form centered models linking unsaturated hydraulic characteristics with spectra IP data.
The resistivity method was used to solve more problems of groundwater in the types alluvium, karstic and another hard development aquifer as an inexpensive and useful method. Some uses of the method in groundwater are: perseverance of depth, thickness and boundary associated with an aquifer (Zohdy, 1969; and Young et al. 1998), conviction of software saline drinking water and fresh water (El-Waheidi, 1992; Yechieli, 2000; and Choudhury et al. , 2001), porosity of aquifer (Jackson et al. , 1978), water content in aquifer (Kessels
The induced polarization (IP) method can be an electrical geophysical approach, which measures the poor decay of voltage in the subsurface following the cessation of your excitation current pulse.
Basically, an electrical current is imparted into the subsurface, such as the electronic resistivity method explained elsewhere in this chapter. Normal water in the subsurface geologic materials (within skin pores and fissures) permits certain geologic material to show an effect called "induced polarization" when an electrical current is applied. Through the application of the electro-mechanical current, electrochemical reactions within the subsurface materials occurs and electricity is stored. Following the electro-mechanical current is turned off the stored electricity is discharged which results in an up-to-date movement within the subsurface materials. The IP equipment then measure the current move.
Thus, in a way, the subsurface material acts as a big electronic capacitor.
The induced polarization method measures the bulk electronic characteristics of geologic systems; these characteristics are related to the mineralogy, geochemistry and grain size of the subsurface materials by which electrical current moves.
Induced polarization measurements are taken together with electronic resistivity measurements using professional IP instruments. Although the IP method historically has been used in mining exploration to find disseminated sulfide deposits, it has also been used effectively in ground drinking water studies to map clay and silt layers which provide as confining items separating unconsolidated sediment aquifers.
Induced polarization data can be collected during a power resistivity review, providing the proper equipment can be used. The addition of IP data to a resistivity investigation improves the quality of the evaluation of resistivity data in three ways: 1) some of the ambiguities encountered in resolving thin stratigraphic layers while modeling electric resistivity data can be reduced by examination of IP data; 2) IP data may be used to distinguish geologic layers which do not answer well to a power resistivity study; and 3) the dimension of another physical property (electrical chargeability) may be used to improve a hydrogeologic interpretation, such as discriminating equally electrically conductive goals such as saline, electrolytic or metallic-ion contaminant plumes from clay layers.
The induced polarization method is more vunerable to sources of cultural interference (steel fences, pipelines, electricity lines, electrical machinery etc) than the electric powered resistivity method. Also, induced polarization equipment requires more electricity than resistivity-alone equipment - this results in bulkier and bulkier field instruments. The cost of an IP system can be much greater resistivity-alone system. This, plus an extra amount of intricacy in the interpretation of the IP data and the skills needed to evaluate and interpret this data may go beyond the resources of some contractors and consultants.
Induced polarization fieldwork tends to be labor intensive and frequently requires 2-3 crew associates. Like electro-mechanical resistivity surveys, induced polarization research require a quite large area, way removed from vitality lines and grounded metallic constructions such as metal fences, pipelines and railroad paths.
Induced polarization tools are similar to electrical resistivity instruments. There are two different types of induced polarization systems. Probably the most frequent kind of IP tool is the "time-domain" system. This instrument transmits a constant electronic current pulse where time the received voltage is sampled for a power resistivity measurement, performing like a standard electrical resistivity system. The electric current is then shut down abruptly by the system, and after a given time delay (several milliseconds) the decaying voltage in the subsurface is sampled at the IP device, averaging over a number of time home windows or "time gates. " The products of measurement are in millivolt-seconds per volt.
The second kind of IP tool is the "frequency-domain" system. In this kind of system, transmitted current is sinusoidal at a specified frequency. Because the system is always on, only a power resistivity dimension can be collected at a specific frequency. To accumulate induced polarization data, two frequencies are widely-used, and a percent change is evident electronic resistivity from measurements accumulated at the two frequencies is determined. This number is named the "percent consistency result" or "PFE, " and the units are dimensionless in percent. Two frequencies commonly used are 0. 3 and 3. 0 Hertz, representing low and high frequency replies, respectively.
Other types of Induced polarization may be encountered, however is not commonly in environmental applications. These include "spectral induced polarization, " "complex resistivity, " and "phase" systems. A detailed description of these systems is beyond the range of this chapter and the reader is preferred to seek advice from the books for an considerable discussion of these systems.
Electrical resistivity surveying is an active geophysical strategy that involves making use of a power current to the planet earth and measuring the subsequent electronic response at the bottom surface to be able to determine physical properties of subsurface materials. The overall basic principle of resistivity tests is the fact dissimilar subsurface materials can be recognized by the dissimilarities in their respected electrical potentials. Variances in electrical potentials of materials are determined by the use of a known amount of electric energy to these materials and the way of measuring of the induced voltage potentials. Ohm's laws areas that the voltage (V) of a power circuit is equal to the electric current (I) times the resistivity (R) of the medium (V-IR). Resistivity surveys are conducted by: 1) applying a known amount of electric energy (I) to the planet earth; 2) measuring the induced voltage (V) ; and, using these two measurements, 3) determining the resistivity (R) of the quantity of globe being surveyed.
Resistivity methods usually require that both current inducing and dimension electrodes to be pushed or driven in to the ground. With hooking up wiring from the tools to the electrodes, electric current is presented into the earth using the existing electrodes and resistivity measurements are performed using different way of measuring electrode configurations and spacings. There are a variety of standardized screening procedures, some of which are defined at length in this section.
Resistivity research identify geoelectric layers somewhat than geologic ones. A geoelectric part is a coating that exhibits a similar electric resistivity response. A geoelectric coating can, but will not always, match a geologic one. For example, an isotropic homogeneous sand, which is saturated with a substance exhibiting an individual conductivity response, can look to be always a single geoelectric covering. The exact same sand, if filled with fluid layers containing different conductivities, (i. e. , salinities) can look to be more than one geoelectric part. The interpretation of resistivity data is therefore best made in conjunction with other geophysical techniques (i. e. , seismic refraction) or typical subsurface investigations (i. e. , garden soil borings
Historically, it was the utilization of galvanic way of measuring systems that offered rise to the IP method which exhibited its high efficiency in resistivity surveys for mineral prospecting and structural applications. Induced polarization is a organic phenomenon managed by many physical and physicochemical reactions associated with passage of current through stones.
The Induced Polarization method of geophysical exploration is something of the rarity. It's the only "new" geophysical method to come into use within over fifty years, and for approximately ten years it has been the most used method on the land surface to find metallic mineral deposits.
The application of that time period domain name IP method in environmental problems has been in days gone by mainly associated with groundwater exploration and with distinguishing between sand aquifers affected by saline intrusion and clay layers _e. g. , Seara and Granda, 1987; Draskovits et al. , 1990; Roy et al. , 1995. . However, cases such as those of Cahyna et al. _1990. and Vogeslang _1995. show its potential in contaminants problems. Cahyna et al. _1990. applied both the DC resistivity and IP methods in a cyanide groundwater contaminants problem where it was found that the IP method identified the contamination of groundwater while this is extremely hard from the resistivity results. E.