Subash Chandra

CSIR-National Geophysical Research Institute · Electrical Geophysics-Groundwater

Resistivity data used for estimating LCR recharge estimates in crystalline hard rock terrain.

The interpretation of ERT data requires inversion, which is challenging due to its nonlinear and ill­posed nature. We aim to solve the inverse problem using a machine learning technique that approximates the complex non-linearity using the data provided without specifying any geophysical or mathematical equations. Speci¦cally, we make use of CNN wi...

In semi‐arid regions as in India, where agriculture relies on groundwater abstraction, increase of water resources availability through managed aquifer recharge (MAR) or rainwater harvesting (RWH) is often perceived as a major solution. Studies on these structures efficiency exists but despite the interest, limited information is available on the t...

Groundwater occurrence in continental flood basalt, where multiple lava flows separated by intertrappean and irregular patterns of lineaments govern the regional hydro-dynamics, is poorly understood. This necessitates a high-resolution hydrogeophysical investigation to devise an effective groundwater management plan. To enhance the knowledge and un...

Crystalline hard-rock aquifers, one of the most complex groundwater systems, are facing serious groundwater management issues due to their limited storage capacity and understanding of their complex hydrogeological characteristics. In this study, we have employed an operational decision support tool to calculate the groundwater budget under variabl...

The growing dependency on groundwater resources in semi-arid hard rock terrains has steadily emerged into desaturation of shallow aquifers limiting them to the sporadically distributed bedrock fractures. Additionally, the heterogeneity in weathering and fracturing distribution elevates the ambiguity for geophysical mapping. This study demonstrates...

Aquifers, major source of fresh water, are depleting in the several parts of the world and posing a threat for a long-term water availability. Managed Aquifer Recharge is one of the potential options to meet the challenge of water security and comprehensive characterization of aquifer system is its essential prerequisite. Aquifer system from soil t...

Plain Language Summary 3D structural mapping of the relict signatures of the past imprint, specially meandering channels buried under soil cover in the current landscape and its linkages with other hydrogeological features that influence the hydrodynamic process, is science question of the utmost importance and practical relevance, particularly to...

The groundwater research was one amongst a few programmes started in the early days of CSIR-National Geophysical Research Institute (CSIR-NGRI). The researchers have worked on a wide range of scientific issues that include development of new instruments and exploration techniques, aquifer mapping and source findings, groundwater modelling and manag...

Ground Penetrating Radar (GPR) is widely applied for rapid and precise mapping of the near surface structures. We performed GPR survey using Terra Sirch-3000 single channel control GPR meter with 2D data collection for civil engineering, environmental, archeological, geological features, aquifer contamination and seawater intrusion studies in India...

We investigated a network of fractures forming the flow paths within the crystalline granitic rocks of an Experimental Hydrogeological Park (EHP) with the help of electrical resistivity surveys. The experimental study located at Managed Aquifer Recharge (MAR) site of EHP has measured a distinct splitting in the apparent resistivity curves for deepe...

Bandikui Watershed in Dausa district is part of Banganga river basin located in eastern Rajasthan. The aquifers in the area are characterized with alluvium underlain by hard rock consisting of quartzite, schists, phyllites, granite and gneisses. Ground Water Resources in the area is continuously depleting and the Bandikui block has been categorized...

Ramgarh area in the desert land of Jaisalmer district, Western Rajasthan is in the midst of one of the most arid climatic region of the World. Water Management in this part of the area therefore poses a tough challenge. Aquifer mapping with the aid of hydrogeologic survey and Surface and heliborne Geophysical Survey reveals the existence of multi-l...

The inverse modelling technique seeks to improve the existing estimates of natural recharge in hard rocks by coupling multiple hydrogeophysical parameters that jointly affect natural hydrogeological processes. This approach involves coupling of an initial set of multiple hydrogeophysical (soil resistivity, bedrock depth and rainfall) parameters in...

Robust transport simulations for sustainable management of groundwater in fractured rocks, need accurate observation data about fracture and matrix processes. In aquifers with naturally hot groundwaters (i.e., 30 ºC in South India), heat injections can become difficult and cumbersome, considering strong density influences. Injecting cold water is a...

Paleochannels typically act as pathways for groundwater movement and provide a potential source of groundwater. Their presence can be helpful in identifying areas suitable for recharge and at times in mitigating contamination problems in afflicted regions. Thus, mapping of paleochannels is significant in the planning and management of groundwater r...

In hardrocks that cover about 20% of the Earth’s surface, it is difficult to locate steady sources for groundwater due to inadequate understanding of the fracture networks. A comprehensive knowledge of fracture distribution at the regional scale is necessary to delineate sustainable aquifers and manage them efficiently. The resistivity maps derived...

Integration of passive seismic and conventional ERT can be applied for characterizing subsurface lithology for groundwater exploration purposes.

Dwindling of groundwater resources in northern India for the past few decades is one of the serious concerns. Groundwater resources in the Baswa-Bandikui watershed located in the state of Rajasthan in northwest India are ‘overexploited,’ and the groundwater level in the area is gradually depleting. In order to find a solution to this serious proble...

AEM data acquired using SkyTEM312 win February 2018, processing using Aarhus Workbench and performed spatially constrained inversion.

Indian port city Surat, the 2nd largest city in Gujarat, 3rd cleanest city of India and 4th fastest growing city of the world, is located in the left bank of Tapi river. It is famous for its food, textile, and polishing over 90% of the world's rough diamond. Recently it has been selected as one of 20 Indian Cities to be developed as a Smart City by...

An innovative approach for regionalizing the 3-D effective-porosity field is presented and applied to two large, overexploited and deeply weathered crystalline aquifers located in southern India. The method derives from earlier work on regionalizing a 2-D effective-porosity field in that part of an aquifer where the water table fluctuates, which is...

With the growing dependence on groundwater, escalating demand, and increasing depletion of aquifers, the Government of India has accorded special emphasis to management of groundwater resources through precise aquifer mapping. We have carried out hydrogeophysical surveys, including airborne electromagnetic (AEM), in six hydrogeologically divergent...

Comprehensive knowledge of aquifer system in the hard rock areas is a prerequisite to develop an effective groundwater management strategy. A majority of the geological formations hosting the aquifers are highly variable and complex with scantily available information especially in the hard rock terrain. In such scenarios the worldwide experience h...

Vertical disposition of the freshwater aquifer lens and their progressive change on lateral scale are relevant to understand the short circuiting of fresh and saline water at coastal areas. Since, half of the world population dwells within 50 km of coast line, the freshwater aquifers at coast are deteriorating at alarming rate. There are well-defin...

In India, particularly in semi-arid and hard rock regions, the declining water table and the reduction in bore well yield as well as net irrigated area are becoming a common situation to the extent that even implementation of rainwater harvesting programs has been unsuccessful. This is mainly attributed to the adoption of ad hoc management strategi...

Water crisis has been felt worldwide and more severely in India. Major parts of India falls under water stress, where the hard rock regions are worst affected. Water security that poses challenge to India’s economy and social development is one of the major concerns. The growing population and escalating water demand has led to huge stress on groun...

Geophysical studies using multichannel analysis of surface waves (MASW) and high-resolution electrical resistivity tomography (HERT) have been jointly carried out on an experimental basis in the field. The motive is to study shallow subsurface features (i.e. faults traces, cavities and palaeo-channels) in the foothill zone of Northwest Himalaya. Th...

Integrated Assessment of Scale Impacts of Watershed Interventions is the outcome of a multi-disciplinary research team of social scientists, hydrologists (groundwater and surface water), modellers; and bio-physical scientists who have worked together over five years to develop an integrated model of the sustainability of biophysical, economic and s...

India is facing serious water challenges and issues due to global climate change. The green revolution, environmental and anthropogenic influences have exacerbated the problem of sustainability of India’s water resources, particularly the groundwater. Although the country is beset with variable water problems as the distribution of water resources...

Palaeo-channel are potential sources of groundwater and help in augmenting groundwater resources by acting as recharge channel due to presence of buried pediments and alluvial fan. These features are natural recharge sites due to high permeability and water storage capacity. In such case, deducing of palaeo-channel and demarcation of its boundaries...

An attempt is made to identify and delineate the groundwater flow direction and rate in a fractured hard rock aquifer in Maheshwaram granite watershed in Andhra Pradesh using multiple tracers such as bromide, iodide and rhodamine-B under both natural and induced conditions. A main well in the center and three observation wells at 25 m in north-nort...

Borehole logging is a very robust tool to accurately locate transitions between weathered layers and fractures in hard rock settings; therefore, it can help substantially in the construction of regional and local hydrogeological models. A simple and low-cost resistivity probe, named dual resistivity logger (DRL), was experimented to map the formati...

Since the beginning of the green revolution in the 1970s, large areas of India have been strongly dependent on groundwater for irrigation which has led to aquifer overexploitation in various parts of the country. To tackle this problem, Indian authorities rely on managed aquifer recharge (MAR). Perennial water resources in semi-arid regions of Sout...

It is hypothesized that hydrochemical parameters can be employed to deduce the basaltic trap thickness and that there exist diverse hydrochemical processes within the existing host rocks along the Deccan Volcanic Province (DVP) margin. Chemical imprints of aquifers, in various flows of flood basalt and fissured zones of granites, had been appraised...

There is a growing concern of seawater intrusion to freshwater aquifers due to groundwater overexploitation in the eastern coastal belt of Southern India. The problem becomes complex in the regions where industrial effluents are also contaminating the freshwater aquifers. In order to understand the hydrochemical complexity of the system, topographi...

Characterization of the shear zone with pole–pole electrical resistivity tomography (ERT) was carried out to explore deep groundwater potential zone in a water scarce granitic area. As existing field conditions does not always allow to plant the remote electrodes at sufficiently far of distance, the effect of insufficient distance of remote electro...

A series of geophysical parameters have been applied with geological perception to resolve the hydrogeological complexities over granitic terrain at Hyderabad, India. Frequent failure of borehole drillings and the thrust conditions of community have prompted a noninvasive suitable tool, applied at small scale for pinpointing potential well site. Ge...

An integrated hydrogeophysical studies in the arsenic affected region of Balia-Patna sector in Middle Ganga Plain of the states of Uttar Pradesh and Bihar in India led to an important finding that the lithological set up plays a major role in understanding the arsenic contamination in groundwater. Although alluvial deposits are known for their hydr...

Geophysical techniques are normally employed to explore the subsurface and determine the anomalies but they are always much larger in dimension. However, a very precise measurement was needed to pin point a misaligned horizontal tunnel made at 47 m depth to intercept an old bore well and rescue a four year child fallen accidently on 9th November at...

Highlights ► Innovative approaches for upscaling and regionalizing K and Sy are proposed. ► Both methods were tested on an unconfined granitic aquifer. ► Log K map uses statistics between K field data and Q/H from irrigation wells. ► 90% of simulated Log K values varies less than 20% from local measurements. ► Sy map: based on a method combining wa...

Two innovative approaches for upscaling and regionalizing hydraulic conductivity and effective porosity at watershed scale are proposed. They are based on the concept that large-scale variations in hydraulic head may characterize large-scale properties and were tested on an unconfined granitic aquifer exposed to deep weathering, located in South In...

A hydrogeochemical analysis of water samples in Middle Ganga Plains (MGP) revealed patchy occurrence of arsenic contamination in groundwater with high spatial variability. An integrated study consists of hydrochemical, 2-d DC resistivity and IP chargeability, and 1-d transient electromagnetic measurements (TEM) was carried out in the Ganga-Son inte...

The structure and hydrodynamic properties of geological discontinuities and of a deeply weathered granite aquifer near these structures are described on the basis of geological, geophysical and hydrodynamic investigations in two sites of South India located along a 20-40-m-wide quartz reef intruding a weathered Archean biotite granite. One of the t...

A lithologically constrained rainfall (LCR) method has been developed to estimate the spatial and temporal natural recharge distribution, a complex and high variable hydrological parameter in hard rocks. The lithological constraints are coupled to the rainfall in terms of soil resistivity (rho(s)) and vadose zone thickness (H). In the absence of a...

Geological discontinuities such as quartz reef, a common geological feature in hard rock terrain occurring as an intrusive body, has been investigated using geophysical methods in order to explore and map the potential aquifer. Electrical resistivity response of quartz reef intrusive in granite host rock has been studied using synthetic simulation...

Knowledge of the spatial distribution of the hydrogeological parameters such as hydraulic conductivity (K) and transmissivity (T) are essential for management and development of groundwater resources. In general, the hydrogeological parameters are estimated by the classical techniques like pumping tests, which are uneconomical and time consuming. T...

Localized electrical conductors are frequently encountered in a variety of problems relating to urban geophysical studies like mapping of pollution plumes, waste disposal, fracture zones in hard rocks, zoning of seismically hazardous areas, etc. Such targets can be represented by shallow 3-D conductors that yield distinct signatures on the surface...

The increasing demand for fresh water has necessitated the exploration for new sources of groundwater, particularly in hard rock terrain, where groundwater is a vital source of fresh water. A fast, cost effective and economical way of exploration is to study and analyze remote sensing data. Interpreted remote sensing data was used to select sites f...

Based on the analogy between Darcy’s law for groundwater flow and Ohm’s law for electric current flow, a methodology has been developed to estimate the hydraulic conductivity and transmissivity of hard rock granite aquifer from geoelectrical parameters. The common parameter, aquifer thickness (t), has been used to combine the two relations and form...

Geophysics plays a major role for characterizing the hard rocks for groundwater studies. The qualitative and quantitative application has increased since past few years due to rapid development and advancement in microprocessors and associated numerical modelling solutions. Although geophysics has ability to probe deep earth interior (say >1000 m),...

Groundwater management becomes imperative for maintaining the sustainability of the resources, which is under stress due to large scale pumping to meet the water requirement by continuous increasing population as well as mismanagement. However, its management requires various hydrogeological parameters such as hydraulic conductivity, transmissivity...

The figures in this article were inadvertently printed in black and white instead of in colour. We apologize very much for this error and provide you here with the corrected printed version. Abstract An integrated study was carried out to investi-gate the subsurface geological conditions in a hard rock en-vironment, with the aim of identifying zone...

An integrated study was carried out to investigate the subsurface geological conditions in a hard rock environment, with the aim of identifying zones with groundwater resource potential. The study, in Bairasagara watershed, Karnataka, India, considered geomorphology, water level, resistivity imaging, self potential, total magnetic field and suscept...

Oozing of water and rise in water level were reported by villagers and media during the third week of January 2005, in parts of Rangareddy, Nalgonda and Mahboobnagar districts of Andhra Pradesh. The event also coincided with the aftermath of the 9.3 magnitude earthquake in Sumatra, Indonesia and the tsunami in the Indian Ocean. The villagers and St...

Natural groundwater recharge is estimated using the injected tracer technique in the Bairasagara watershed of Kolar district, Karnataka (India) comprising of medium grained granite and granitic gneiss with weathering/fracturing up to 46 m depth. On a macroscopic scale, it is estimated that the weathered granites act as a uniform body having a recha...

In hard rocks, groundwater accumulation occurs only because of secondary porosity developed due to wea- thering, fracturing, faulting, etc., which is highly vari- able and varies sharply within very short distances, contributing to near-surface inhomogeneity. This can affect the current-flow pattern in their surroundings and consequently distort th...