Magnetotelluric (MT) is a passive EM technique that uses variations in the naturally occurring Electromagnetic fields to model the subsurface resistivity structure. Due to the broad range of frequency (104 – 10-4 Hz) utilized in MT, this tool can give subsurface information of the order of a few 10’s meters to a few 100’s kms. Therefore, MT finds applications in shallow exploration studies for various earth resources and deep crustal and upper mantle imaging to understand the dynamics and evolution of the lithosphere. Since resistivity of earth materials shows a huge range of variation (10-2 to 106) as compared to other physical properties, measurement of resistivity property helps to distinguish between different rock formations and in-situ physical conditions. In hydrocarbon studies, the generally conductive sedimentary formation can be easily mapped from the encompassing resistive formations. Therefore, MT is used as a complementary tool along with seismic data to de-risk exploration. In seismically poor geological settings, such as volcanic or basaltic covered and complex overthrust settings, MT is more effective and provides better constraints on the target structure.

CSIR-NGRI has the capabilities and expertise to take up any challenging geological problems using MT. NGRI has a modern Instrument pool to record both high-frequency and low-frequency MT signals, an indigenously developed processing approach and code, an industry-standard modelling software package, academic programs for data analysis, skilled scientific and technical staff for high-quality data acquisition & analysis, and expertise in 2D and 3D Interpretation, which includes in-house developed 3D Inversion algorithm.

Since the foundation of the institute groundwater is one of the thrust areas and a group (Electrical and Heliborne Geophysics, EHG) of dedicated researchers have been carrying R&D projects to address the groundwater issues on theoretical and applied fronts. A number of methodologies using electrical (ground and borehole), electromagnetic, hydrological and geostatistical methods have been developed for groundwater exploration, assessment and management. The group, recently has developed core competency on advanced hydrogeophysics using integrated approach of heliborne, ground and borehole geophysics as well as hydrogeological studies for aquifer mapping and management. Heliborne geophysics supported by ground and borehole data has successfully demonstrated high-resolution aquifer mapping in diverse hydrological settings of India that has brought many new insights such as mapping of potential groundwater bedrock fracture network, tectonic pathways and associated aquifers in hard rocks, precise 3D distribution of sand and clay in alluvial settings, coastal salinity, discovering buried paleochannels. The group has recently established a new tool viz., Electrical-field Vector Resistivity Imaging (EVRI) for hydrological applications in urban areas with considerably greater depth, and developing capability for handling of bigdata and its translation in hydro-geophysical models and parametrization.

Apart from geophysical surveys and hydrogeophysical modeling, estimation of groundwater fluxes, aquifer parameter estimation and characterization such as natural recharge, hydraulic conductivity and transmissivity, pollution studies, natural treatment of wastewater using wetland have been developed. Grounwater flow and mass transport modeling as well as pollution study have been integral part of the R&D projects. Further, the group has been carrying long term study to monitor the hydrographs since 1991 in Maheshwaram watershed to understand the complexity of hardrock hydrodynamic and established experimental hydrological park at NGRI campus Chautuppal for controlled and new experiments. The group is also involed in dedicated study of critical zone i.e. hydrogeological characteistics of vadose zone. The Group has also contributed to Surat smart city, mapping of paleochannel and river aquifer linkages, tunnel projects in hills of Himalaya and Western Ghats, industrical and societal projects.