Faculty Publications
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Item Parameter estimation and vulnerability assessment of coastal unconfined aquifer to saltwater intrusion(2012) Mahesha, A.; Vyshali; Lathashri, U.A.; Ramesh, H.The focus of the present work is to characterize a tropical, coastal aquifer and to carry out its vulnerability to saltwater intrusion using hydrogeological parameters. The characterization of the aquifer involves pumping tests, vertical electrical sounding, and water quality analysis carried out at 41 monitoring wells. The area under investigation lies between two tropical, seasonal, tidal rivers, i.e., Pavanje and Gurpur rivers, joining the Arabian on the west coast of India. The aquifer is predominantly shallow and unconfined, having moderate to good groundwater potential with transimissivity and specific yield ranging from 49.2 to 461:4 m2/day and 0.00058 to 0.2805, respectively. The electrical resistivity tests indicated that the thickness of the aquifer ranges from 18 to 30 m. The study also investigates the saltwater affected areas in the region the vertical electrical sounding and water quality analysis. The resistivity results revealed several probable isolated saltwater intruded pockets in the region with resistivity less than 70 Om. From the salinity analysis of water, the locations that are affected during February to May (summer) and throughout the year are identified. The wells that are located close to the coast (< 350 m) and at lower elevations (well bottom < +1 m) were found to be saline throughout the year. Also, wells along the banks of the river show considerable salinity (> 200 ppm) during the summer period from tidal inflow along the rivers. The water samples were also analyzed for chloride to bicarbonate ratios during December to May at all the monitoring wells and were found to be exceeding the allowable limit at several locations. The saltwater vulnerability maps are derived for the area by the index-based method using the hydrogeological parameters. The method was found to be effective while compared to the field observations. The results from the analysis indicate that the aquifer is medium to highly vulnerable to saltwater intrusion at majority of the locations. The impact of projected sea level rise by 0.25 and 0.50 m from the climate change is also assessed on the vulnerability of the region to saltwater intrusion. © 2012 American Society of Civil Engineers.Item Estimating anisotropic heterogeneous hydraulic conductivity and dispersivity in a layered coastal aquifer of Dakshina Kannada District, Karnataka(Elsevier B.V., 2018) Priyanka, B.N.; Kumar, M.S.; Mahesha, M.The solution for the inverse problem of seawater intrusion at an aquifer scale has not been studied as extensively as forward modeling, because of the conceptual and computational difficulties involved. A three-dimensional variable-density conceptual phreatic model is developed by constraining with real-field data such as layering, aquifer bottom topography and appropriate initial conditions. The initial aquifer parameters are layered heterogeneous and spatially homogeneous that are based on discrete field measurements. The developed conceptual model shows poor correlation with observed state variables (hydraulic head and solute concentration), signifying the importance of spatial heterogeneity in hydraulic conductivity and dispersivity of all the layers. The conceptual model is inverted to estimate the anisotropic spatially varying hydraulic conductivity and the longitudinal dispersivity at the pilot points by minimizing the least square error of state variables across the observation wells. The inverse calibrated model is validated for the hydraulic head at validation wells and the solute concentration is validated with equivalent solute concentration derived from the electrical resistivity, which shows good results against the field measurements. The verification of estimated anisotropic hydraulic conductivity with the electrical resistivity tomography image shows good agreement. This investigation gives an insight about constraining the highly parameterized inverse model with real-field data to estimate spatially varying aquifer parameters for an effective simulation of the seawater intrusion in a layered coastal aquifer. © 2018 Elsevier B.V.Item Delineation of Groundwater Potential Zones using Integrated Approach in Semi-Arid Hard Rock Terrain, Kanavi Halla Sub-Basin, Belagavi District, Karnataka(Springer, 2020) Patil, V.B.B.; Lokesh, K.N.; Krishnamurthy, M.P.; Nadagoudar, H.V.Water scarcity has become a major problem especially in arid and semi-arid regions due to insufficient rainfall throughout the globe. This has led in serious search for groundwater resources. Kanavi Halla Sub Basin (KHSB) of Ghataprabha River basin drained by Ghataprabha River, Belagavi District of Karnataka state in India has been considered for present study. Electrical resistivity survey was carried out at selected sites using Schlumberger method with four electrode configuration. A total of 22 Vertical Electrical Sounding (VES) were conducted throughout KHSB and representative of different litho units were considered. Data obtained were then interpreted using curve matching technique with IPI2Win software. The interpreted graphs show three to six layers. The various interpreted curve types are of AAK-type, HA-type, A-type, KH-type, HAA-type, KQH-type, AK-type, K-type, HQH-type, H-type and AKQH-type. From the results it shows that the maximum number of curves are associated with A type which refers to hard rock terrain, whereas curve associated with H type indicates water potential site. The expected subsurface strata are interpreted on the basis of observed bore well drilling data. Borewell log reveals soil formation followed by moderately weathered formation, weathered jointed formation, jointed formation, hard formation from top to bottom. Further deep, the formation is devoid of joints and fractures. Therefore, the weathered, jointed formation may be interpreted as water bearing zone. 2-D geo-electric section has been drawn using IPI2WIN over eight selected trends to understand the geometry of the aquifer formed. The investigation was meant to characterize the aquifer in KHSB along with the risk assessment for contaminants through seepage in terms of protective capacity with the help of Dar-Zarrouk (D-Z) parameters such as longitudinal unit conductance (S), longitudinal resitivity (?1), transverse unit resistance (T), transverse resistivity (?t), Electrical anisotropy(?) and root mean square resistivity (?m). These were evaluated to know the aquifer conditions in order to demarcate the freshwater bearing zones. South eastern part of KHSB might be contaminated and 30% of the area is weak to poor capacity protective zone for contaminants. The work adequately highlights the practical use of geophysical techniques, combination of geo-electrical modelling, D-Z parameters, borehole log in the groundwater resource assessment process. This technique is highly recommended for the area with similar geological setup. © 2020, Geological Society of India.Item Electrical resistivity, remote sensing and geographic information system approach for mapping groundwater potential zones in coastal aquifers of Gurpur watershed(Taylor and Francis Ltd., 2021) Virupaksha, H.S.; Lokesh, K.N.Electrical resistivity method and RS & GIS techniques are very much useful in identification of potential aquifer zones for exploitation, management and recharge of groundwater. Vertical Electrical Soundings are conducted at 35 locations in Gurpur watershed using Schlumberger array. The thematic layers like porosity, transmissivity and hydraulic conductivity are prepared using electrical resistivity data. Total of 13 thematic layers are used for vector integration and identification of Groundwater Potential Zones (GWPZ). The numerical weights and ranks are assigned to the themes based on their relationship with groundwater. The findings shows that the depth to bedrock varies from 9.1 to 44.4 m and most of the mid land and low land region shows moderate to high depths of about 25–44 m. The GWPZ are classified into five classes namely, Very Good (?21.02 km2), Good (?231.35 km2), Moderate (?420.76 km2), Poor (?185.05 km2) and Very Poor (?19.56 km2). The Good and Moderate categories cover ?75% of total area. © 2019 Informa UK Limited, trading as Taylor & Francis Group.Item Insulator-to-metal-like transition in thin films of a biological metal-organic framework(Nature Research, 2023) Sindhu, P.; Ananthram, K.S.; Jain, A.; Tarafder, K.; Ballav, N.Temperature-induced insulator-to-metal transitions (IMTs) where the electrical resistivity can be altered by over tens of orders of magnitude are most often accompanied by structural phase transition in the system. Here, we demonstrate an insulator-to-metal-like transition (IMLT) at 333 K in thin films of a biological metal-organic framework (bio-MOF) which was generated upon an extended coordination of the cystine (dimer of amino acid cysteine) ligand with cupric ion (spin-1/2 system) – without appreciable change in the structure. Bio-MOFs are crystalline porous solids and a subclass of conventional MOFs where physiological functionalities of bio-molecular ligands along with the structural diversity can primarily be utilized for various biomedical applications. MOFs are usually electrical insulators (so as our expectation with bio-MOFs) and can be bestowed with reasonable electrical conductivity by the design. This discovery of electronically driven IMLT opens new opportunities for bio-MOFs, to emerge as strongly correlated reticular materials with thin film device functionalities. © 2023, The Author(s).Item Investigation on Estimation and Prediction of Resistivity of Limestone Rocks based on Physico-Mechanical Properties of Rocks(World Researchers Associations, 2025) Varalakshmi, P.; Kumar Reddy, S.K.; Murthy, C.S.N.Prediction of rock resistivity indirectly is of paramount importance in several geophysical and civil engineering applications. Physico-mechanical properties such as p-wave velocity, porosity and dry density tend to have a good correlation with electrical resistivity of rocks. Conventional approaches for measuring resistivity produce results which may consume more time and efforts and are not accessible every location. To overcome this, an Artificial Neural Network (ANN) model was evolved in this study, using Python and TensorFlow. The model was trained using known values to predict electrical resistivity of unknown and similar materials. Actual results of resistivity were compared with resistivity values obtained from ANN model. The obtained values were evaluated for reliability using non-linear regression models. It was observed that predicted resistivity values generated using p-wave velocity were more reliable. Also, validations made based on the ANN model, using mean absolute error (MAE) and average residuals indicate that P-wave velocity is the most reliable predictor, achieving the lowest MAE (4.638) and near-zero residuals (-0.005), while porosity and dry density showed higher errors and weaker correlations. This study revealed that the ANN model developed results in reliable predictions of rock resistivity based on p-wave values. © 2025, World Researchers Associations. All rights reserved.