Dewashish Kumar - Academia.edu (original) (raw)
Papers by Dewashish Kumar
Journal of Earth System Science, May 4, 2021
Groundwater recharge is a hydrological process where water flows from sub-surface layers to the w... more Groundwater recharge is a hydrological process where water flows from sub-surface layers to the water table of the aquifer and is the backbone of the hydrogeological system. The present study is carried out in a granitic hard rock aquifer region within and surroundings of the CSIR-NGRI campus, Hyderabad. The aim of this study to identify the potential groundwater recharge zone(s) using GIS based multi-criteria decision making (MCDM) along with sub-surface mapping from Electrical Resistivity Tomography (ERT) technique. The assigned weight of the different thematic layers of surface and sub-surface parameters and their specific characteristics was determined based on their relative contribution to the groundwater recharge and thus the normalized weight was computed using MCDM technique. These thematic layers were integrated with the help of ArcGIS to accurately identify the recharge zones within the study region. The resulting recharge map has been categorized into five classes viz., very poor, poor, moderate, good and very good. Numerically 23.11% of the study area is in a moderate zone of recharge, 4.97% in good and very good zone, while 71.92% falls under the poor and very poor zone, i.e., unsuitable for groundwater recharge. The recharge zone map of the study area is found to be in agreement with 2D inverted resistivity models for two different time periods, which revealed distinct geological features and thus identified the near surface recharge property, where recharge zone resistivity values lie between ~20 and 70 Ω.m up to 11 m depth. Thus, the integrated results from the present study delineated groundwater recharge zone(s) for sustainable groundwater resources in the granitic hard rock system.
Journal of Geophysical Research: Earth Surface, 2016
The full-text may be used and/or reproduced, and given to third parties in any format or medium, ... more The full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that: • a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.
Characterization of groundwater flow regime was carried oUt in typical crystalline rocks of Dhanb... more Characterization of groundwater flow regime was carried oUt in typical crystalline rocks of Dhanbad in the Saraidhela area of northern India. It is a hard rock terrain and consists of fractured felspathic gneiss and quartzite. Three sets of fracture were studied and a conceptual model of aquifer was established using NETWORK program. Out of three sets, Set I and Set III are the major conduits for groundwater flow. The cardinal aquifer parameter like porosity, permeability, velocity and flow rate are obtained. The velocity calculated for Set I and Set III are 1.5207 * 10-09m/s and 1.5193 * 10-09mls respectively for a head difference of 0.001 m. The porosity is less than I % in both the sets and the permeability for the two sets are 1.4 * 1004ill/day and 1.0 * 1004m/day respectively.
AEG Publication, 2002
Characterization of groundwater flow regime was carried out in typical crystalline rocks of Dhanb... more Characterization of groundwater flow regime was carried out in typical crystalline rocks of Dhanbad in the Saraidhela area of northern India. It is a hard rock terrain and consists of fractured felspathic gneiss and quartzite. Three sets of fracture were studied and a conceptual model of aquifer was established using NETWORK program. Out of three sets, Set I and Set III are the major conduits for groundwater flow. The cardinal aquifer parameter like porosity, permeability, velocity and flow rate are obtained. The velocity calculated for Set I and Set III are 1.5207 * 10 -09 m/s and 1.5193 * 10 -09 m/s respectively for a head difference of 0.001 m. The porosity is less than 1% in both the sets and the permeability for the two sets are 1.4 * 10 04 m/day and 1.0 * 10 04 m/day respectively.
Journal of Earth System Science
Groundwater recharge is a hydrological process where water flows from sub-surface layers to the w... more Groundwater recharge is a hydrological process where water flows from sub-surface layers to the water table of the aquifer and is the backbone of the hydrogeological system. The present study is carried out in a granitic hard rock aquifer region within and surroundings of the CSIR-NGRI campus, Hyderabad. The aim of this study to identify the potential groundwater recharge zone(s) using GIS based multi-criteria decision making (MCDM) along with sub-surface mapping from Electrical Resistivity Tomography (ERT) technique. The assigned weight of the different thematic layers of surface and sub-surface parameters and their specific characteristics was determined based on their relative contribution to the groundwater recharge and thus the normalized weight was computed using MCDM technique. These thematic layers were integrated with the help of ArcGIS to accurately identify the recharge zones within the study region. The resulting recharge map has been categorized into five classes viz., very poor, poor, moderate, good and very good. Numerically 23.11% of the study area is in a moderate zone of recharge, 4.97% in good and very good zone, while 71.92% falls under the poor and very poor zone, i.e., unsuitable for groundwater recharge. The recharge zone map of the study area is found to be in agreement with 2D inverted resistivity models for two different time periods, which revealed distinct geological features and thus identified the near surface recharge property, where recharge zone resistivity values lie between ~20 and 70 Ω.m up to 11 m depth. Thus, the integrated results from the present study delineated groundwater recharge zone(s) for sustainable groundwater resources in the granitic hard rock system.
Journal of Applied Geophysics, 2007
The Vertical Electrical Sounding (VES) is the most widely used geophysical technique for groundwa... more The Vertical Electrical Sounding (VES) is the most widely used geophysical technique for groundwater prospecting. However its interpretation has been subjected to several indistinctness and efforts are on to tackle them. Vertical Electrical Soundings were carried out at 86 sites in a small watershed of about 60 km 2 in a granitic terrain with the objective of delineating the aquifer layer parameters viz. weathered zone, fissured zone and depth to the bedrock. The thickness and resistivity of the weathered, fissured zone and depth to bedrock were determined from VES data. Due to wide variation in resistivity and in the absence of good resistivity contrast, the resolution has been less precise and thus the layer parameters interpreted could be ambiguous. Based on the VES results and hydrogeological considerations, 25 wells were initially drilled and later on 8 more wells were drilled intercepting through the bedrock. In addition, lithologs from 6 additional wells are available in the same watershed. Thus with the help of lithologs from 39 wells, thicknesses of various layers and bedrock depths were determined. This set of data from the lithologs were analysed geostatistically and an estimation of these parameters was made at all the 86 locations using a final variogram obtained from the variographic analysis. This has provided a range for the estimated values of the above three parameters using the standard deviation of the estimation error. The interpreted parameters from VES were compared with the range thus obtained in the above procedure. The interpreted VES results that could not be found within the stipulated range provided by the geostatistical estimation, were categorized separately and a suitable reinterpretation was made for them by fitting some parameters obtained from the nearby well data. After a few iterations, a large number of VES results were found falling in the estimated range and thus reduced the ambiguities in the VES results. The study has provided a new and additional method of reducing the ambiguities in VES interpretation as well as providing a quality indicator to each interpretation.
Journal of Applied Geophysics
Journal of the Geological Society of India, 2016
Two dimensional Electrical Resistivity Tomography (ERT) investigation along with Time Domain Indu... more Two dimensional Electrical Resistivity Tomography (ERT) investigation along with Time Domain Induced Polarization (TDIP) investigation covering 1.6 km line were carried out at 3 natural recharge sites in a overexploited groundwater granite watershed, situated in a semi arid region in the state of Telangana, India. At these sites, shallow and/ or deep moisture influx measurements were also carried out using injected tritium tracer and neutron moisture probe. The watershed is covered by sandy loam to silt loam soil, receives an average annual rainfall of 620 mm with the pre monsoon groundwater level ranging from 8m to 29m bgl. The spot investigations were done to assess and understand the recharge process and groundwater potential in terms of resistivity/conductivity and moisture characteristics of the subsurface rock formation. The measured and 2D inverted resistivity models shows soil, highly weathered and moderately weathered zones up to a depth of 22m followed by semi-weathered and massive granites up to the maximum depth of 78m. The resistivity values of the soil and shallow weathered zones varying between ~5-50 Ohm.m up to a depth of 12m. The large variation in resistivity values of the soil and weathered zone is probably indicative of large variation in the moisture potential. The resistivity models clearly mapped the granitic hard rock structure in the depth range of 22-78m, which has a significant resistivity contrast (~1500-11000 Ohm.m) with respect to the overlying semi weathered layers. The modeled 2D resistivity data at a site in two perpendicular directions shows similar geological structure and geoelectric layers. The TDIP dataset shows insignificant chargeability variations (1-7 mV/V) up to the investigated depth of 78m, which probably indicates low to moderate moisture and groundwater potential in the vadoze and saturated zones of the aquifer. The experimental investigations provide scope for assessing dynamic recharge and groundwater potential at selected sites in an overexploited granite watershed in the present geological context.
Current Science
Besides the high resolution offered by HERT, the resistivity models obtained using different elec... more Besides the high resolution offered by HERT, the resistivity models obtained using different electrode arrays differ significantly in geological structure and resistivity range. We combine the apparent resistivity data from multiple arrays to provide single resistivity model of high resolution as 'composite method'. Initially, the method was tested on physical model data obtained over horizontal marble sheet kept in water. The parameters of target (resistivity, geometry, thickness) noticed in the resistivity model corresponding to composite method are appropriately matching with the true parameters. Finally, the method was applied to the data from Mahabubnagar, Telangana, India for groundwater studies. The resistivity model obtained using the proposed method has shown good match with regional hydro-geology and borehole data. The results from physical model as well as field data suggest plausible resolution enhancement in composite methodology for resolving thin layer(s) in 2D and 3D electrical resistivity tomography and induced polarization (IP) studies.
Journal of Earth System Science
Katpal in Mesoarchaean Sukinda Ultramafic Complex (SUC) hosts chromitites within the ultramafic r... more Katpal in Mesoarchaean Sukinda Ultramafic Complex (SUC) hosts chromitites within the ultramafic rocks emplaced in the Tomka–Daitari–Mahagiri greenstone belt, Singhbhum Craton. Chromite deposits occur as seams, lenses or pockets in ultramafic–mafic rocks mainly comprising serpentinised dunite, peridotite and gabbro. Chromite deposits at Kalrangi, Kaliapani and its precincts in SUC are currently being exploited by M/s. Odisha Mining Corporation (OMC), whereas their continuity is elusive in the subsurface in the Katpal area, Sukinda, Odisha. High-resolution electrical resistivity tomography (ERT) was carried out in quarry-G of M/s. OMC in Katpal on four profiles each with a profile length 400 m and each of them is separated at an interval of ~100 m to capture and visualise a maximum anomaly variation within the host rock. The objectives of this study are to understand the behaviour of chromite seams vis-à-vis with a high-resolution electric potential signal with depths and to evolve a method to discriminate chromitites from the host rock both in horizontal and vertical directions with depths, which can be used to locate the extension of chromite seams around the study area. The interpretation of the ERT models revealed interesting resistivity anomalies, which is inferred as chromite associated with the ultramafic host rock in the area. Exploratory borehole data of the area confirmed the subsurface occurrence of chromitites within 22–40 m depths as lensoidal bodies within the mafic–ultramafic rocks. The chromite ore is mapped as low-resistive zones with a resistivity of ~35–200 Ω m and extended up to a depth of 170 m within the high-resistive (>500 Ω m) host rocks. Two distinct chromite bands were identified at different depths: 20–40 and 90–110 m based on the specific resistivity contrast and were validated using the existing shallow borehole data. The second band is highly folded whereas the first band resembles sill-like feature within the host rock. The electrical tomography technique can be aptly applied in an unknown area in SUC to establish the extension of the chromite ore body, its resistive signature and their variation with depths within the host rock for future resource prospecting and exploitation in the given geological setting of the area. The chromite ore is mapped as a low-resistivity signature and its extension is delineated as a low-resistivity anomaly of ~35–200 Ω m. The electrical resistivity models indicate low resistivity as chromite and high-resistivity as ultramafic rock (~500–10,000 Ω m) up to a depth of 170 m. The light green up to yellow bands in the inverted resistivity models characterise various grades of mineralisation within the host rock setting. The chromite ore is mapped as a low-resistivity signature and its extension is delineated as a low-resistivity anomaly of ~35–200 Ω m. The electrical resistivity models indicate low resistivity as chromite and high-resistivity as ultramafic rock (~500–10,000 Ω m) up to a depth of 170 m. The light green up to yellow bands in the inverted resistivity models characterise various grades of mineralisation within the host rock setting.
Journal of the Geological Society of India, 2021
Electrical conductivity (EC) and temperature logging were carried out in twenty-five borewells/pi... more Electrical conductivity (EC) and temperature logging were carried out in twenty-five borewells/piezometers in a hard rock region of Telangana, India at an interval of 1 and 2 m right from the water table till the bottom of the borewell to study the fracture zones at different depths and to recognize temperature variation with depths. The temperature and EC profiles of the groundwater were recorded at regular intervals along the depths of the borewells, the sensitivity of the sensor of the logger being limited to 0.1 K An attempt was made to calculate the vertical component of the water flux in 25 borewells using the temperature profile measurements in these borewells by applying the heat convection and conduction equation and taking into account the volumetric heat capacity of water and the thermal conductivity of rocks (in the present study, granite). The temperature data was first linearly fitted. The dispersion that would exist in thermal conductivity under the assumption as unif...
Integrated study combining electrical resistivity tomography, geology, hydrogeomorphology, and we... more Integrated study combining electrical resistivity tomography, geology, hydrogeomorphology, and weighted overlay analysis of various surface and subsurface thematic layers proved to be a very useful tool for evaluating the heterogeneous hard aquifer systems for groundwater assessment and development. A comprehensive study was carried out at representative and varied geological settings viz., Chotanagpur Granite-Gneiss Complex (CGGC), Ranchi has been accomplished from geology and geophysical datasets. The electrical resistivity tomography results revealed potential target zones at three sites in the study area up to a maximum of 170 m depth with a large variation in aquifer resistivity ranging from 80 to 800 Ω.m. These significant findings depicted a good correlation and are validated with the lithology in the surrounding of the resistivity tomography results. Nevertheless, the weighted overlay technique act as an essential tool for spatial analysis and interpretation of potential gro...
Journal of geophysics, 2002
Characterization of groundwater flow regime was carried out in typical crystalline rocks of Dhanb... more Characterization of groundwater flow regime was carried out in typical crystalline rocks of Dhanbad in the Saraidhela area of northern India. It is a hard rock terrain and consists of fractured felspathic gneiss and quartzite. Three sets of fracture were studied and a conceptual model of aquifer was established using NETWORK program. Out of three sets, Set I and Set III are the major conduits for groundwater flow. The cardinal aquifer parameter like porosity, permeability, velocity and flow rate are obtained. The velocity calculated for Set I and Set III are 1.5207 * 10 -09 m/s and 1.5193 * 10 -09 m/s respectively for a head difference of 0.001 m. The porosity is less than 1% in both the sets and the permeability for the two sets are 1.4 * 10 04 m/day and 1.0 * 10 04 m/day respectively.
Geophysical studies carried out in granitic hard rock terrain of semi-arid regions in India have ... more Geophysical studies carried out in granitic hard rock terrain of semi-arid regions in India have resulted in developing various relationships between geophysical properties and hydrogeological parameters. A new approach has been developed to refine and improve the VES (Vertical Electrical Sounding) interpretation with quantitative information from geology using borewells data and geostatistics. This provides a guideline with quantitative information for further improvement of the VES reinterpretation, which helps in sorting the results in various categories of varying reliability. This methodology has important applications in groundwater development and management programs (e.g., implementation of future drilling). A combined Axial Pole-dipole and Schlumberger (CAPS) configuration method of VES has been introduced to identify the lateral near surface inhomogeneities (NSI), which normally occur in the hard rock and misleads the VES interpretations. Mathematical calculation has yield...
Journal of Earth System Science, May 4, 2021
Groundwater recharge is a hydrological process where water flows from sub-surface layers to the w... more Groundwater recharge is a hydrological process where water flows from sub-surface layers to the water table of the aquifer and is the backbone of the hydrogeological system. The present study is carried out in a granitic hard rock aquifer region within and surroundings of the CSIR-NGRI campus, Hyderabad. The aim of this study to identify the potential groundwater recharge zone(s) using GIS based multi-criteria decision making (MCDM) along with sub-surface mapping from Electrical Resistivity Tomography (ERT) technique. The assigned weight of the different thematic layers of surface and sub-surface parameters and their specific characteristics was determined based on their relative contribution to the groundwater recharge and thus the normalized weight was computed using MCDM technique. These thematic layers were integrated with the help of ArcGIS to accurately identify the recharge zones within the study region. The resulting recharge map has been categorized into five classes viz., very poor, poor, moderate, good and very good. Numerically 23.11% of the study area is in a moderate zone of recharge, 4.97% in good and very good zone, while 71.92% falls under the poor and very poor zone, i.e., unsuitable for groundwater recharge. The recharge zone map of the study area is found to be in agreement with 2D inverted resistivity models for two different time periods, which revealed distinct geological features and thus identified the near surface recharge property, where recharge zone resistivity values lie between ~20 and 70 Ω.m up to 11 m depth. Thus, the integrated results from the present study delineated groundwater recharge zone(s) for sustainable groundwater resources in the granitic hard rock system.
Journal of Geophysical Research: Earth Surface, 2016
The full-text may be used and/or reproduced, and given to third parties in any format or medium, ... more The full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that: • a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.
Characterization of groundwater flow regime was carried oUt in typical crystalline rocks of Dhanb... more Characterization of groundwater flow regime was carried oUt in typical crystalline rocks of Dhanbad in the Saraidhela area of northern India. It is a hard rock terrain and consists of fractured felspathic gneiss and quartzite. Three sets of fracture were studied and a conceptual model of aquifer was established using NETWORK program. Out of three sets, Set I and Set III are the major conduits for groundwater flow. The cardinal aquifer parameter like porosity, permeability, velocity and flow rate are obtained. The velocity calculated for Set I and Set III are 1.5207 * 10-09m/s and 1.5193 * 10-09mls respectively for a head difference of 0.001 m. The porosity is less than I % in both the sets and the permeability for the two sets are 1.4 * 1004ill/day and 1.0 * 1004m/day respectively.
AEG Publication, 2002
Characterization of groundwater flow regime was carried out in typical crystalline rocks of Dhanb... more Characterization of groundwater flow regime was carried out in typical crystalline rocks of Dhanbad in the Saraidhela area of northern India. It is a hard rock terrain and consists of fractured felspathic gneiss and quartzite. Three sets of fracture were studied and a conceptual model of aquifer was established using NETWORK program. Out of three sets, Set I and Set III are the major conduits for groundwater flow. The cardinal aquifer parameter like porosity, permeability, velocity and flow rate are obtained. The velocity calculated for Set I and Set III are 1.5207 * 10 -09 m/s and 1.5193 * 10 -09 m/s respectively for a head difference of 0.001 m. The porosity is less than 1% in both the sets and the permeability for the two sets are 1.4 * 10 04 m/day and 1.0 * 10 04 m/day respectively.
Journal of Earth System Science
Groundwater recharge is a hydrological process where water flows from sub-surface layers to the w... more Groundwater recharge is a hydrological process where water flows from sub-surface layers to the water table of the aquifer and is the backbone of the hydrogeological system. The present study is carried out in a granitic hard rock aquifer region within and surroundings of the CSIR-NGRI campus, Hyderabad. The aim of this study to identify the potential groundwater recharge zone(s) using GIS based multi-criteria decision making (MCDM) along with sub-surface mapping from Electrical Resistivity Tomography (ERT) technique. The assigned weight of the different thematic layers of surface and sub-surface parameters and their specific characteristics was determined based on their relative contribution to the groundwater recharge and thus the normalized weight was computed using MCDM technique. These thematic layers were integrated with the help of ArcGIS to accurately identify the recharge zones within the study region. The resulting recharge map has been categorized into five classes viz., very poor, poor, moderate, good and very good. Numerically 23.11% of the study area is in a moderate zone of recharge, 4.97% in good and very good zone, while 71.92% falls under the poor and very poor zone, i.e., unsuitable for groundwater recharge. The recharge zone map of the study area is found to be in agreement with 2D inverted resistivity models for two different time periods, which revealed distinct geological features and thus identified the near surface recharge property, where recharge zone resistivity values lie between ~20 and 70 Ω.m up to 11 m depth. Thus, the integrated results from the present study delineated groundwater recharge zone(s) for sustainable groundwater resources in the granitic hard rock system.
Journal of Applied Geophysics, 2007
The Vertical Electrical Sounding (VES) is the most widely used geophysical technique for groundwa... more The Vertical Electrical Sounding (VES) is the most widely used geophysical technique for groundwater prospecting. However its interpretation has been subjected to several indistinctness and efforts are on to tackle them. Vertical Electrical Soundings were carried out at 86 sites in a small watershed of about 60 km 2 in a granitic terrain with the objective of delineating the aquifer layer parameters viz. weathered zone, fissured zone and depth to the bedrock. The thickness and resistivity of the weathered, fissured zone and depth to bedrock were determined from VES data. Due to wide variation in resistivity and in the absence of good resistivity contrast, the resolution has been less precise and thus the layer parameters interpreted could be ambiguous. Based on the VES results and hydrogeological considerations, 25 wells were initially drilled and later on 8 more wells were drilled intercepting through the bedrock. In addition, lithologs from 6 additional wells are available in the same watershed. Thus with the help of lithologs from 39 wells, thicknesses of various layers and bedrock depths were determined. This set of data from the lithologs were analysed geostatistically and an estimation of these parameters was made at all the 86 locations using a final variogram obtained from the variographic analysis. This has provided a range for the estimated values of the above three parameters using the standard deviation of the estimation error. The interpreted parameters from VES were compared with the range thus obtained in the above procedure. The interpreted VES results that could not be found within the stipulated range provided by the geostatistical estimation, were categorized separately and a suitable reinterpretation was made for them by fitting some parameters obtained from the nearby well data. After a few iterations, a large number of VES results were found falling in the estimated range and thus reduced the ambiguities in the VES results. The study has provided a new and additional method of reducing the ambiguities in VES interpretation as well as providing a quality indicator to each interpretation.
Journal of Applied Geophysics
Journal of the Geological Society of India, 2016
Two dimensional Electrical Resistivity Tomography (ERT) investigation along with Time Domain Indu... more Two dimensional Electrical Resistivity Tomography (ERT) investigation along with Time Domain Induced Polarization (TDIP) investigation covering 1.6 km line were carried out at 3 natural recharge sites in a overexploited groundwater granite watershed, situated in a semi arid region in the state of Telangana, India. At these sites, shallow and/ or deep moisture influx measurements were also carried out using injected tritium tracer and neutron moisture probe. The watershed is covered by sandy loam to silt loam soil, receives an average annual rainfall of 620 mm with the pre monsoon groundwater level ranging from 8m to 29m bgl. The spot investigations were done to assess and understand the recharge process and groundwater potential in terms of resistivity/conductivity and moisture characteristics of the subsurface rock formation. The measured and 2D inverted resistivity models shows soil, highly weathered and moderately weathered zones up to a depth of 22m followed by semi-weathered and massive granites up to the maximum depth of 78m. The resistivity values of the soil and shallow weathered zones varying between ~5-50 Ohm.m up to a depth of 12m. The large variation in resistivity values of the soil and weathered zone is probably indicative of large variation in the moisture potential. The resistivity models clearly mapped the granitic hard rock structure in the depth range of 22-78m, which has a significant resistivity contrast (~1500-11000 Ohm.m) with respect to the overlying semi weathered layers. The modeled 2D resistivity data at a site in two perpendicular directions shows similar geological structure and geoelectric layers. The TDIP dataset shows insignificant chargeability variations (1-7 mV/V) up to the investigated depth of 78m, which probably indicates low to moderate moisture and groundwater potential in the vadoze and saturated zones of the aquifer. The experimental investigations provide scope for assessing dynamic recharge and groundwater potential at selected sites in an overexploited granite watershed in the present geological context.
Current Science
Besides the high resolution offered by HERT, the resistivity models obtained using different elec... more Besides the high resolution offered by HERT, the resistivity models obtained using different electrode arrays differ significantly in geological structure and resistivity range. We combine the apparent resistivity data from multiple arrays to provide single resistivity model of high resolution as 'composite method'. Initially, the method was tested on physical model data obtained over horizontal marble sheet kept in water. The parameters of target (resistivity, geometry, thickness) noticed in the resistivity model corresponding to composite method are appropriately matching with the true parameters. Finally, the method was applied to the data from Mahabubnagar, Telangana, India for groundwater studies. The resistivity model obtained using the proposed method has shown good match with regional hydro-geology and borehole data. The results from physical model as well as field data suggest plausible resolution enhancement in composite methodology for resolving thin layer(s) in 2D and 3D electrical resistivity tomography and induced polarization (IP) studies.
Journal of Earth System Science
Katpal in Mesoarchaean Sukinda Ultramafic Complex (SUC) hosts chromitites within the ultramafic r... more Katpal in Mesoarchaean Sukinda Ultramafic Complex (SUC) hosts chromitites within the ultramafic rocks emplaced in the Tomka–Daitari–Mahagiri greenstone belt, Singhbhum Craton. Chromite deposits occur as seams, lenses or pockets in ultramafic–mafic rocks mainly comprising serpentinised dunite, peridotite and gabbro. Chromite deposits at Kalrangi, Kaliapani and its precincts in SUC are currently being exploited by M/s. Odisha Mining Corporation (OMC), whereas their continuity is elusive in the subsurface in the Katpal area, Sukinda, Odisha. High-resolution electrical resistivity tomography (ERT) was carried out in quarry-G of M/s. OMC in Katpal on four profiles each with a profile length 400 m and each of them is separated at an interval of ~100 m to capture and visualise a maximum anomaly variation within the host rock. The objectives of this study are to understand the behaviour of chromite seams vis-à-vis with a high-resolution electric potential signal with depths and to evolve a method to discriminate chromitites from the host rock both in horizontal and vertical directions with depths, which can be used to locate the extension of chromite seams around the study area. The interpretation of the ERT models revealed interesting resistivity anomalies, which is inferred as chromite associated with the ultramafic host rock in the area. Exploratory borehole data of the area confirmed the subsurface occurrence of chromitites within 22–40 m depths as lensoidal bodies within the mafic–ultramafic rocks. The chromite ore is mapped as low-resistive zones with a resistivity of ~35–200 Ω m and extended up to a depth of 170 m within the high-resistive (>500 Ω m) host rocks. Two distinct chromite bands were identified at different depths: 20–40 and 90–110 m based on the specific resistivity contrast and were validated using the existing shallow borehole data. The second band is highly folded whereas the first band resembles sill-like feature within the host rock. The electrical tomography technique can be aptly applied in an unknown area in SUC to establish the extension of the chromite ore body, its resistive signature and their variation with depths within the host rock for future resource prospecting and exploitation in the given geological setting of the area. The chromite ore is mapped as a low-resistivity signature and its extension is delineated as a low-resistivity anomaly of ~35–200 Ω m. The electrical resistivity models indicate low resistivity as chromite and high-resistivity as ultramafic rock (~500–10,000 Ω m) up to a depth of 170 m. The light green up to yellow bands in the inverted resistivity models characterise various grades of mineralisation within the host rock setting. The chromite ore is mapped as a low-resistivity signature and its extension is delineated as a low-resistivity anomaly of ~35–200 Ω m. The electrical resistivity models indicate low resistivity as chromite and high-resistivity as ultramafic rock (~500–10,000 Ω m) up to a depth of 170 m. The light green up to yellow bands in the inverted resistivity models characterise various grades of mineralisation within the host rock setting.
Journal of the Geological Society of India, 2021
Electrical conductivity (EC) and temperature logging were carried out in twenty-five borewells/pi... more Electrical conductivity (EC) and temperature logging were carried out in twenty-five borewells/piezometers in a hard rock region of Telangana, India at an interval of 1 and 2 m right from the water table till the bottom of the borewell to study the fracture zones at different depths and to recognize temperature variation with depths. The temperature and EC profiles of the groundwater were recorded at regular intervals along the depths of the borewells, the sensitivity of the sensor of the logger being limited to 0.1 K An attempt was made to calculate the vertical component of the water flux in 25 borewells using the temperature profile measurements in these borewells by applying the heat convection and conduction equation and taking into account the volumetric heat capacity of water and the thermal conductivity of rocks (in the present study, granite). The temperature data was first linearly fitted. The dispersion that would exist in thermal conductivity under the assumption as unif...
Integrated study combining electrical resistivity tomography, geology, hydrogeomorphology, and we... more Integrated study combining electrical resistivity tomography, geology, hydrogeomorphology, and weighted overlay analysis of various surface and subsurface thematic layers proved to be a very useful tool for evaluating the heterogeneous hard aquifer systems for groundwater assessment and development. A comprehensive study was carried out at representative and varied geological settings viz., Chotanagpur Granite-Gneiss Complex (CGGC), Ranchi has been accomplished from geology and geophysical datasets. The electrical resistivity tomography results revealed potential target zones at three sites in the study area up to a maximum of 170 m depth with a large variation in aquifer resistivity ranging from 80 to 800 Ω.m. These significant findings depicted a good correlation and are validated with the lithology in the surrounding of the resistivity tomography results. Nevertheless, the weighted overlay technique act as an essential tool for spatial analysis and interpretation of potential gro...
Journal of geophysics, 2002
Characterization of groundwater flow regime was carried out in typical crystalline rocks of Dhanb... more Characterization of groundwater flow regime was carried out in typical crystalline rocks of Dhanbad in the Saraidhela area of northern India. It is a hard rock terrain and consists of fractured felspathic gneiss and quartzite. Three sets of fracture were studied and a conceptual model of aquifer was established using NETWORK program. Out of three sets, Set I and Set III are the major conduits for groundwater flow. The cardinal aquifer parameter like porosity, permeability, velocity and flow rate are obtained. The velocity calculated for Set I and Set III are 1.5207 * 10 -09 m/s and 1.5193 * 10 -09 m/s respectively for a head difference of 0.001 m. The porosity is less than 1% in both the sets and the permeability for the two sets are 1.4 * 10 04 m/day and 1.0 * 10 04 m/day respectively.
Geophysical studies carried out in granitic hard rock terrain of semi-arid regions in India have ... more Geophysical studies carried out in granitic hard rock terrain of semi-arid regions in India have resulted in developing various relationships between geophysical properties and hydrogeological parameters. A new approach has been developed to refine and improve the VES (Vertical Electrical Sounding) interpretation with quantitative information from geology using borewells data and geostatistics. This provides a guideline with quantitative information for further improvement of the VES reinterpretation, which helps in sorting the results in various categories of varying reliability. This methodology has important applications in groundwater development and management programs (e.g., implementation of future drilling). A combined Axial Pole-dipole and Schlumberger (CAPS) configuration method of VES has been introduced to identify the lateral near surface inhomogeneities (NSI), which normally occur in the hard rock and misleads the VES interpretations. Mathematical calculation has yield...