Rock Terrain Research Articles

Application of machine learning and fuzzy AHP for identification of suitable groundwater potential zones using field based hydrogeophysical and soil hydraulic factors in a complex hydrogeological terrain

The eastern section of West Bengal grapples with limited surface water availability in its hard rock terrain, compounded by a semi-arid climate, variable rainfall, and a plateau topography, prompting communities to adapt groundwater water-use practices, leading to unsustainable extraction and misuse. Thus, the novel objective of the present research was to produce groundwater potential maps by comparing machine learning techniques with a Fuzzy MCDM model using specific field-based conditioning factors. In the first step, 285 wells were identified, of which 70 percent were used for training and 30 percent for the validation of the models. Secondly, field-based conditioning factors including, longitudinal conductance (SC), longitudinal resistance (ρl), transverse resistance (TR), coefficient of electrical anisotropy (λ), resistivity of formation (ρm), fracture porosity (φf), reflection coefficients (r), hydraulic conductivity (K), transmissivity(Tr), bulk density, porosity, permeability, soil moisture content and water holding capacity were used to analyze the association between these conditioning factors and groundwater occurrences. In the following steps, the XGBoost, Random Forest, and Naïve Bayes models were executed using the training dataset, and factor weights were calculated using Fuzzy Analytical Hierarchy Process of Extent analysis method. To validate and compare the performance of four models, ROC curves, AUCs, MCAs, and correlation plots were used. In general, all four models were successful in evaluating the potential of groundwater occurrences. The predictive capability of the XGBoost techniques with the highest AUC values (0.79) and the highest correlation value (0.78) is superior to those of other machine learning and MCDM models. Geophysical survey revealed that transmissivity and hydraulic conductivity of the aquifer of the river basin range from 1.55 to 440.11 m/day and 10.15–2253 m2/day, indicating a moderate to good hydrodynamic potential. Planners and engineers can use such groundwater potential maps to manage water resources effectively.

Anisotropic effect of shear zone on groundwater potentiality in crystalline hard rock terrain

Assessment of potential groundwater recharge sites and sustainable water resource management in semi-arid crystalline rock terrain is a challenging task. Globally, analysis of remote sensing satellite imagery data for delineation of groundwater potential zones over sheared crystalline hard rock terrains has been fairly successful. But there is no existing study present at our disposal which discusses the factors controlling the inconsistent groundwater potentiality that exits along the shear zones. This study attempts to analyse the major geological factors controlling the irregular groundwater potentiality of shear zones within older crystalline rock terrain. Therefore, the study area selected for this analysis is the Purulia district of West Bengal, NE India, composed mostly of Precambrian metamorphic rocks i.e., quartzite, granite gneisses, porphyroclastic granite-gneiss, quartzo-feldspathic-granite-gneiss, mylonitic granites, quartz-biotite-granite gneiss, quartzites, carbonatites and phyllites. Satellite imagery study of IRS-P6 LISS IV standard FCC image reveals the presence of two bifurcating shear zones namely North Purulia Shear Zone (NPSZ) and South Purulia Shear Zone (SPSZ) over the study area. Careful analysis of rock structure, different lithotypes, soil thickness, electrical resistivity tomography data and water table data with an emphasis on high water table fluctuation, shows a strong spatial relation between the potentially good groundwater recharge zones and the branching/confluence sites of shear zones present in the study area. The study constructs an attempt to demonstrate the relationship between shear zone conjunctions and significant groundwater recharge sites in Precambrian crystalline fractured-rock aquifer system.

Decisive significance of lineaments on groundwater occurrence in the Khapri watershed of Deccan Volcanic Province (DVP), district Dangs, Western India

This study investigates the influence of geological lineaments on groundwater occurrence in the Khapri watershed, Dangs district, Gujarat, where rugged terrain and less transmissible basaltic rocks limit infiltration despite high rainfall (2000 mm). Lineaments were mapped using IRS LISS-III satellite data and eight hill-shades generated at various azimuth angles (45°, 90°, 135°, 180°, 225°, 270°, 315°, and 360°) from Carto-Digital Elevation Model (DEM) in GIS environment to ensure maximum extraction. These lineaments, validated through Google Earth and ground-truthing, were categorized into positive (ridges, plateaus, dykes) and negative (joints, fractures, straight stream segments) based on their contribution to water infiltration. The comprehensive lineament map revealed dominant NNE-SSW and ENE-WSW orientations. Positive lineaments largely induce runoff, while negative lineaments support water infiltration. The study indicates a moderate correlation between lineament densities and the groundwater regime. Regions with high negative lineament density exhibit lower groundwater fluctuation, indicating better groundwater occurrences, while areas with high positive lineament density show greater fluctuation, indicating lesser groundwater occurrence. Linear regression analysis indicates that 48% and 50% of the variation in groundwater fluctuation is explained by positive and negative lineament density, respectively. This analysis emphasizes the importance of identifying and mapping negative lineaments for targeting groundwater resources in hard rock terrains.

Improving groundwater vulnerability assessment in structurally controlled hard rock aquifer: insight from lineament density and land use/land cover pattern.

A comprehensive seasonal assessment of groundwater vulnerability was conducted in the weathered hard rock aquifer of the upper Swarnrekha watershed in Ranchi district, India. Lineament density (Ld) and land use/land cover (LULC) were integrated into the conventional DRASTIC and Pesticide DRASTIC (P-DRASTIC) models and were extensively compared with six modified models, viz. DRASTIC-Ld, DRASTIC-Lu, DRASTIC-LdLu, P-DRASTIC-Ld, P-DRASTIC-Lu, and P-DRASTIC-LdLu, to identify the most optimal model for vulnerability mapping in hard rock terrain of the region. Findings were geochemically validated using NO3- concentrations of 68 wells during pre-monsoon (Pre-M) and post-monsoon (Post-M) 2022. Irrespective of the applied model, groundwater vulnerability shows significant seasonal variation, with > 45% of the region classified as high to very high vulnerability in the pre-M, increasing to ̴67% in post-M season, highlighting the importance of seasonal vulnerability assessments. Agriculture and industries' dominant southern region showed higher vulnerability, followed by regions with high Ld and thin weathered zone. Incorporating Ld and LULC parameters into DRASTIC-LdLu and P-DRASTIC-LdLu models increases the 'Very High' vulnerability zones to 17.4% and 17.6% for pre-M and 29.4% and 27.9% for post-M, respectively. Similarly, 'High' vulnerable zones increase from 32.5% and 25% in pre-M to 33.8% and 35.3% in post-M for respective models. Model output comparisons suggest that modified DRASTIC-LdLu and P-DRASTIC-LdLu perform better, with accurate estimations of 83.8% and 89.7% for pre-M and post-M, respectively. However, results of geochemical validation suggest that among all the applied modified models, DRASTIC-LdLu performs best, with accurate estimations of 34.4% and 20.6% for pre-M and post-M, respectively.

Analyzing water level variability in Odisha: insights from multi-year data and spatial analysis

A comprehensive analysis of long-term water level trends is essential for freshwater sustainability. Given that Odisha heavily relies on agriculture, the monitoring and management of groundwater and its fluctuations are imperative for ensuring future sustainability in the state. Here, we analyzed the trend in Groundwater using water level data for a 30-year period (1990–2020) for the entire Odisha region. Moreover, to determine the long term variability, critical zones of future groundwater variability and controlling parameters of the water level change, we used spatio-temporal water level data of 746 locations. Water level rise of coastal districts during post-monsoon (POM), corresponds to the intensity of rainfall received, thus rising, however other districts of Odisha, showing decline in water level during the same season is due to shortage of rainfall, increase in population at a sudden, and over pumping due to industrial activities. Similarly, during pre-monsoon (PRM), water level shows an increasing trend in hard rock terrain of Odisha implying rabi crop irrigation, high density drainage network and lesser population density. Feature selection techniques were used in this study to know the parameters controlling most to this water level fluctuation in the entire Odisha state. Precipitation followed by landuse & landcover, lithology and population density are controlling the most for the long term water level change. Drainage, elevation, lithology and slope are positively related to the water level change while others are negatively related. It is also inferred that the districts like Mayurbhanj, Sundargarh, Keonjhar, Kandhamal, Boudh, Dhenkanal, Gajapati, Koraput and Kalahandi contain most of the high critical zone concerning future availability of groundwater while most of the coastal regions are safe.

Assessment to locate potential deep aquifer systems using lithological logs, pumping tests and electromagnetic surveys in hard rock terrain of Dodoma urban area, Tanzania

The Dodoma region located in Central Tanzania is a semi-arid area characterised by scarce surface water resources. Because of climate change and dependence on groundwater resources in the Dodoma urban area, there is currently an increased demand for water due to low groundwater recharge and high groundwater withdrawals due to the growing population. There is therefore a need to explore potential deep aquifer systems around the Dodoma urban area to meet the increasing water demand. This study uses lithological logs, pumping tests, and electromagnetic survey data to delineate the subsurface lithologies to locate potential deep aquifer system in the area. Results show that the shallow aquifer system is unconfined in some areas with resistivity values ranging from 11 to 28 Ωm and semi-confined in other areas with resistivity values ranging from 19 to 27 Ωm. The unconfined aquifer extends up to 60 m, while the semi-confined aquifer extends between 50–55 m and 65–120 m. The study found a potential deep aquifer system at a depth of between 200 and 290 m, with resistivity values ranging from 11 to 20 Ωm. Currently, this deep aquifer system has not been exploited as most boreholes in the area are only up to 150 m deep. The main lithology in the study area is weathered and fractured granite, with different degrees of weathering and fracturing, indicating a hard-rock aquifer system. This study adds valuable knowledge on the location of potential deep aquifer systems in the area for proper groundwater utilisation and management.

Identification of Groundwater Prospecting Zones in Hard Rock Terrain Using Remote Sensing and GIS Techniques: A Case Study of Pora River Sub Basin, Central India

In the present study groundwater prospecting zones (GPZ) have been carried out sing hydrogeological parameter and to delineate the GPZ of Pora River sub basin in hard rock terrain Nagpur districts, Maharashtra, India using satellite data and GIS techniques. For the preparation of groundwater potential map different thematic maps viz. geology, lineaments/fracture, geomorphology, slope and land use/land cover were prepared and assigned with spatial analysis techniques in ARC GIS and assigned values as per their groundwater properties. From the total 122.342 km area the ground water prospect zones the 30.402 km area shows the good category, good to moderate is 25.862 km, moderate 17.592 km, moderate to poor 5.932 km, Poor 6.192 km, Habitation gives 35.702 km and very good to good 0.4353312 km respectively.

Diagenesis, Provenance, Tectonic Setting and Palaeoclimate of the Eocene Kopili Sandstone, Assam, India: A Petrographic Study

Abstract The Eocene Kopili Sandstone outcropping in the North Cachar Hills (NCHs) of Assam, India, was petrographically studied to unravel its diagenetic features, provenance, tectonic setting and palaeoclimate conditions. The modal analysis of the Kopili Sandstone reveals that the detrital mineralogy is dominated by quartz (48.78 to 83.70 %), with variable amounts of rock fragments (0.37 to 7.35 %), feldspar (0.37 to 8.33 %), micas (0.36 to 7.84 %) and subordinate amount of heavy minerals. The matrix and cement content varies from 9.88 to 21.50 % and 1.12 to 19.41 % respectively. The Kopili Sandstone is classified as quartz arenite to sub lithic arenite. Compaction, cementation, dissolution and replacement are the observed diagenetic processes in the studied sandstones. Diagenetic transformations are manifested in the fractured detrital grains, overgrowth of quartz, corrosion of grain boundaries of quartz, modification of grain boundaries, and silica and iron oxide cement precipitation in the interstices of the framework grains. The provenance is of granite-gneissic rock terrain. The detritus in the depositional basin is derived predominantly from craton interior with minor input from recycled orogen. The study discerns humid palaeoclimate conditions for the Kopili Sandstone.

Evaluation of groundwater quality for irrigation purposes in hard rock terrain of Southern India using water quality indices modelling

Industrial effluent discharge threatens both agricultural productivity and drinking water quality by depleting groundwater, contaminating surface water and demanding high-quality irrigation water. This study evaluates the influence of urbanization and agricultural activities on the groundwater quality in Perundurai, focusing on its suitability for both drinking and agriculture. A total fourty samples of groundwater were randomly taken from bore wells. The principal cations and anions were analyzed revealed their dominance order: Na Ca > Mg > K and Cl > SO4 > F > NO3. The water quality index (WQI) analysis found that around 89% samples are unsuitable for drinking. The PI value indicates that 2% samples have poor permeability and elevated risk of waterlogging make it unsuitable for field use. Analysis of the Piper diagram reveals the dominance of alkaline earth cations (Ca, Mg) over alkali metals (Na, K) and weak acids (HCO3, CO3) over strong acids (Cl, SO4), indicating specific hydrogeochemical facies. From the US salinity diagram (USSL), C4S1 samples (30%) exhibit low alkalinity but a hazardous high salinity which impairs their capacity to retain water. Wilcox classification identified that 27% samples exhibit potential limitations for irrigation due to elevated sodium content. Contamination of groundwater due to ion leaching, sewage discharge and runoff is a significant environmental concern with potential health implications.

Stability Evaluation of Unlined Circular Tunnels in Sloping Rock Terrain Using Adaptive Finite Element Limit Analysis

Stability Evaluation of Unlined Circular Tunnels in Sloping Rock Terrain Using Adaptive Finite Element Limit Analysis

Delineation of lineaments for groundwater prospecting in hard rocks: inferences from remote sensing and geophysical data

Egypt is grappling with water scarcity challenges, which are exacerbated by extensive urban development in arid coastal regions with rugged terrain. Although desalinated water is an alternative source in the remote Halayeib region of Southeast Egypt, its cost increases reliance on groundwater from the intricate aquifers. This study aims to accurately delineate hydro-structural features, known as lineaments, and assess their impact on the groundwater conditions in this promising region. This integrated approach involves the assessment of various spaceborne sensors, including optical (Landsat 8), Digital Elevation Models (ALOS and ASTER-DEMs), and radar (Sentinel-1), using geospatial and geostatistical techniques within the Geographic Information System (GIS). Radar-based sensors, particularly the Sentinel-1A vertical–vertical (S1A VV) polarization, outperform all other datasets in extracting lineaments, yielding 4883 lineaments that correspond to the regional geological faults. These lineaments trend in NE–SW, NNE–SSW, NW–SE, and E-W directions. The results also indicated that both digital elevation models (DEMs) were less effective, showing different orientations with azimuth angles. S1A VV proved to be highly effective in identifying subsurface fractured hard rock terrains beneath thin sedimentary covers, especially in the flat coastal area of Wadi Serimatai, where they intersected natural drainage pathways. Geoelectrical sections confirmed that there are orthogonal subsurface faults extending from fractured basement aquifers to near-surface layers. These faults align with the NE-SW and NNE-SSW directions observed in S1A VV lineaments. Geostatistical analysis revealed that S1A VV structural lineaments, lithological, and hydrogeological factors influence the occurrence of groundwater. This emphasizes the structural control over groundwater and its significant impact on water flow and storage. The study provides valuable insights for groundwater management, guiding decisions related to the development of groundwater resources.

Groundwater Quality Assessment from a Hard Rock Terrain Kundalika River Basin, Beed District, Maharashtra, India

In the study area, the primary source of water is groundwater for the drinking and irrigation purpose. For the assessment of groundwater quality results of 48 groundwater samples in post& pre monsoon season for the year 2021 & 2022 were carried out from Kundalika River basin Beed District, Maharashtra. The pH values of groundwater reveal that slightly alkaline in nature. The electric conductivity varies from 290 to 2640 µS/cm; the total dissolved solids (TDS), alkalinity, total hardness, calcium, magnesium, sodium, potassium, chloride measured. Most of TDS values of groundwater samples less 1000 mg/l indicate suitable for drinking and irrigation purpose. In the piper trilinear diagram, it is observed that 80% groundwater samples in post monsoon season 2021 and pre monsoon season 2022 fall in the Ca-HCO3 region and remaining 20 % groundwater samples of both season falls in mixed type such as Ca-Na-HCO3 region. According to Wilcox’s diagram all groundwater samples are good for irrigation purpose except 2 % samples of post monsoon season 2021 and pre monsoon season 2022 are doubtful to unsuitable area for irrigation use. Various water quality indices like: EC, SAR, SSP, RSC, MAR and KR shows that most water samples are suitable for irrigation uses. U. S. Salinity Laboratory Diagram shows that all the groundwater samples belongs to C2-S1,C3-S1,C3-S1 and C3-S2 category suggesting a medium to high salinity and alkalinity; this can be good for irrigation purpose, with few exceptions under specific conditions.

A decade drought monitoring through enhanced and standardized vegetation index in isolated karst environment: Nusa Penida Island, Bali, Indonesia

Nusa Penida is one of the regions in Indonesia that vunarablely experiences extreme drought. The worst drought occurred in December 2019, coinciding with the Covid-19 pandemic outbreak. At that time, drought caused major crises in many local primary economic aspects, such as clean-water crises and local crop failure. The situation worsened after the global pandemic lockdown was imposed. Many tourism-related hospitalities (i.e., hotels, resorts, and restaurants) also have crashed. Isolated karst islands such as Nusa Penida Island pose significant challenges for water and agricultural land management. Geologically, this area consists of hilly carbonate rock terrain, a lack of proper aquifers, low precipitation, and tend to had high concentrations of dissolved Ca and Mg in its water. These conditions make many areas less preferable for settlements and traditional agriculture. In this study, we assessed the area using geospatial data for drought monitoring. We analyzed weekly-22 years of data (18/02/2000-18/02/2022 or 507 weeks data) to understand the period pattern of seasonal droughts in Nusa Penida over the past decade. This study used compiled satellite raster-images data to compute the Enhanced Vegetation Index (EVI) to express the Standardized Vegetation Index (SVI), which is sensitive to vegetation change during drought. The results showed that the longest droughts in Nusa Penida occurred from December 2000 to October 2001 (20 weeks) and Feb 2002 to Jan 2023 (21 weeks). The worst droughts occurred in December 2019 (SVI: -1.903 to -1.236), 2006 (SVI: -1.872 to -1.374), and 2002 (SVI: up to -0.136). There are patterns in which droughts in Nusa Penida tend to occur towards the end of the year, including at the end of 2022. Additionally, we detected some evergreen areas in Nusa Penida that require further investigation. These areas potentially act as natural permanent aquifers even during droughts. Furthermore, this study provides more insights for other comprehensive research, especially to enhance mitigation policies for near-future drought periods in Nusa Penida.

Late Quaternary tectono‐geomorphological investigations of Zanskar Basin, NW Himalaya, India, using geospatial techniques

AbstractGeospatial techniques play a crucial role in geomorphic studies, particularly in the challenging terrains like mountainous regions, inaccessible areas and densely vegetated landscapes, where geomorphic features cannot be recorded easily. Tectono‐geomorphologic observations provide important clues regarding the landscape evolution, morpho‐dynamics and ongoing tectonism of the region. The present study has been carried out in the Zanskar Basin (ZB), located to the south of the Indus Tsangpo Suture Zone (ITSZ), in the hinterland of the NW Himalaya. This study has been carried out to assess and evaluate active tectonics by employing tectono‐geomorphic analysis, dynamics in drainage networks, geomorphological field observations and the Geographic Information System (GIS) environment. High‐resolution satellite images, topographic maps and the Shuttle Radar Topography Mission (SRTM) Digital Elevation Model (DEM) were used to generate primary data sets, which were corroborated with field investigations for valid inferences. The geometry of the ZB suggests that continuous tectonic activity exerts first‐order control on the overall shape, size and structure of the ZB. This first‐order response is clearly reflected in the landforms modified by tectonic processes, namely, linear mountain fronts, elongated shape and tilting of the basin, braided and meandering river courses and lower stream length gradient index values in hard rock terrain. The ZB exhibits several eye‐catching geomorphic features, such as well‐defined triangular facets with wide base lengths and wine‐glass valleys with small outlets along the footwall block of the Zanskar Shear Zone/South Tibetan Detachment System (ZSZ/STDS), as well as the presence of wind gaps, water gaps, bedrock incision, incised and entrenched valleys, narrow gorges and a high incision rate inferring active tectonics and recent uplift in the region. In addition, the existence of uplifted river terraces, as well as the stepped morphology of fans and strath terraces, suggests that the region is experiencing recent activity and ongoing tectonic uplift. These modified geomorphic characteristics suggest that the hinterland, which is part of the NW Himalaya, is tectonically quite active and has experienced a differential rate of tectonics during its evolution. The quantified geomorphic indices and their relations with the tectonics, climate and erosion activity infer that the basin geometry is mostly controlled by the ZSZ/STDS that dips 20°–70° NE, the south‐dipping Zanskar Counter Thrust (ZCT) and other local tectonic elements like the Choksti Thrust (CT), Stondgey Thrust, Zangla Thrust and tectonic structures. The synergised results of quantified geomorphic indices and tectono‐geomorphic evidence in the ZB strongly indicate that both the past and ongoing tectonism have significantly shaped and modified geomorphology of the ZB.

Estimation Criteria for Static Rock Mass Deformability Modulus for Rock-Socket Design in Metamorphic Rock Masses

This study investigates the most appropriate empirical criteria to estimate the static rock mass deformability modulus (𝐸𝑚) in the design of rock-sockets in cast-in-situ bored pile construction. The in-situ 𝐸𝑚 values are initially estimated through back analysis of static pile load test data. Secondly, the rock mass deformability estimated from back analysis (𝐸𝑚b) are tested statistically against selected established empirical equations to determine whether the latter are appropriate for use in metamorphic rock terrain of Sri Lanka. It is found that the existing empirical criterion based on the square root of intact unconfined compressive strength (𝜎𝑐) derived from back analysis of pile load test results is appropriate for weak-poor rock masses. For strong-poor rocks, it is recommended to employ the equation based on 𝜎𝑐', and in general the two equations generate lower and upper bound solutions. The equation based on intact deformability modulus (𝐸𝑖) performs well in strong-excellent quality rock masses, while the equations based on 𝐸𝑖 and rock quality designation (𝑅QD) are found to be appropriate for weak-fair to excellent rock masses. Finally, a new set of equations appropriate for different rock mass types have been proposed through regression analysis along with appropriate design measures to be adopted.

Application of second-order geoelectric indices in determination of groundwater vulnerability in hard rock terrain in SW. Nigeria

Application of second-order geoelectric indices in determination of groundwater vulnerability in hard rock terrain in SW. Nigeria

Appraisal of Water Resources Development Action Plan for Groundwater Recharge in Raghunathapalli Watershed, Jangaon District, Telangana State, India

Water is elixir of life which needs regular assessment for maintaining ecological balance. Micro watershed wise (a few thousand hectares of extent) water resource action plan is need of the hour especially for a hard rock terrain like Raghunathapalli watershed of Jangaon District. Geologically, the area is underlain by Quartzite and Pelitic Schist of Older Metamorphics and Leuco Granite / Grey Alkali FelpsarGranite Terrain (Peninsular Gneissic Complex) belonging to Archeans. The Archeans are intruded at several places by several Pegmatite Veins and Basic Dolerite Dykes. The average annual rainfall of the study area for the past 19 years is 946 mm and that of monsoonal rainfall is 746 mm. In order to do artificial ground water recharge, the study and analysis of parameters that control the ground water recharge is very important for effective ground water recharge. The spatio-temporal variations in rainfall, regional/local distribution in geological formations and geomorphic composition of various units have led to uneven occurrence and distribution of water resources. Different thematic layers like Geology, Geomorphology, Stream Network, Micro Watersheds, Digital Elevation Model, Contours (2m), Base Layers, Soil and Ground Water Potential maps are prepared using Geospatial technologies like Remote Sensing & GIS. Existing Recharge Structures are marked using 1:25,000 scale Survey of India Toposheets and new locations are updated with high resolution satellite imagery. Micro watershed wise Water Balance studies are carried out and Water Resources Development Action Plan is prepared using Ridge to Valley concept with new artificial recharge structures like Check Dams (22), Percolation Tanks (10), Contour Trenches (68Kms), Subsurface Dyke (2), Farm Pond (268), Recharge Pit (179), Recharge Shaft (16), Desilting Tank (24 nos) etc at suitable terrain conditions. Newly proposed locations for constructions of Rainwater harvesting structures in the gap areas will improve the ground water regime and improves the sustainability of wells for agriculture in the drought prone area of Raghunathapalli watershed. Thus Geospatial technologies are cost effective tools for management and conservation of water resources.

Estimation of groundwater level and storage changes using innovative trend analysis (ITA), GRACE data, and google earth engine (GEE)

Groundwater is the supreme source of fresh water and the third-largest water resource around the world. But in recent decades, groundwater-related issues in Manbhum Singhbhum Plateau have been significantly increasing day by day. In this plateau region, overuse of groundwater and inappropriate irrigation has greatly harmed the ecosystem, triggering salinity, increasing contamination of groundwater. Therefore, it is essential to estimate the magnitude of groundwater storage changes and water table fluctuation in both pre and post-monsoon seasons in this plateau fringe. The principal objectives of this study are i) to investigate groundwater level changes in the last two decades using observed water level data and ii) to estimate groundwater storage changes using satellite-derived datasets in a hard rock terrain region of India. The Innovative Trend Analysis (ITA) technique has been applied for its better visual interpretation and advantage in serial correlation than the traditional Mann-Kendell test. Gravity Recovery and Climate Experiment (GRACE) gridded data have been processed to obtain a time series trend of mean Equivalent Water Thickness (EWT) and soil moisture has been estimated in Google Earth Engine (GEE). Therefore, soil moisture is subtracted from terrestrial water storage (TWS) to estimate the changes in groundwater storage (GWS) in this plateau fringe. ITA result indicates that approximately 40% and 67.5% of monitoring sites had seriously dropping tendencies of groundwater table in pre and post-monsoon seasons respectively. Simultaneously, maximum groundwater storage (9.484 cm) occurred in Jul 2004 (wet months) whereas a minimum of −30.21 in March 2016 (dry months). Overall results indicate massive decline in groundwater table and groundwater storage. The main reasons for these alarming challenges are geological structure and excessive extraction of groundwater for drinking and irrigation purposes. These research findings will help to further investigations and perform crucial well-organized management of water resources in this part of Manbhum-Singhbhum Plateau.

Determination of groundwater potential zones on the eastern slope of Mount Cameroon using geospatial techniques and seismoelectric method

In complex hard rock terrain where the population suffers from water scarcity, the use of site-specific single-method surface geophysical surveys to prospect for groundwater is a common practise. However, this has not completely solved the problem of drilling dry wells. To combat this failure, geospatial data and the analytical hierarchy process (AHP) are being used as supporting techniques to increase the chance of success. This study had the aim of generating a groundwater potential zones (GWPZ) map of the complex strato-volcanic terrain of Buea by integrating geospatial techniques, AHP, and the seismoelectric method. Five factors influencing groundwater recharge were used to define the groundwater potential zones. Via the AHP and weighted overlay methods, five classes of groundwater potential zones were delineated: very poor, poor, moderate, good, and very good. More than half of the study area has good to very good groundwater potential. Lastly, the GWPZ model is validated with an iso-conductivity map from a seismoelectric survey and existing static water level data. The iso-conductivity map revealed four main conductivity zones that correlate positively with the GWPZ map. The northwestern part of the study area is characterised by moderate groundwater potential, poor formation conductivity, and dry boreholes. There is an uneven distribution of groundwater and variable water table depth in the area. The results of this study are very encouraging, and the integrated approach used has proven to be efficient in determining groundwater potential zones in complex volcanic terrain.

Mapping of groundwater potential zones by integrating remote sensing, geophysics, GIS, and AHP in a hard rock terrain

Groundwater is a life-sustaining resource that provides for society's daily water needs, supports industrial development, promotes agricultural activities, and maintains ecological balance. In groundwater resource studies, integrating remote sensing, geophysical data, and GIS tools play a critical role in monitoring, analyzing, and protecting groundwater resources for water resources development and management. This study used a comparative approach since it is less labour-intensive, inexpensive, and efficient. The potential groundwater zones were determined by integrating various data sources such as remote sensing, geophysical, and collateral data and using the Analytic Hierarchy Process (AHP) method. Fifteen different thematic layers, including geology, geomorphology, lineament density, topsoil resistivity, topsoil thickness, weathered zone resistivity, weathered zone thickness, first fractured resistivity, first fractured thickness, second fractured resistivity, second fractured thickness, slope, land use/land cover, drainage density, and rainfall, were mapped in this process. The results show that the northern part of the study area has a relatively higher response of groundwater potential zones than the southern portion. Agricultural areas near surface water bodies and forests, characterized by shallow to moderately weathered pediments and pediplains, exhibit favourable groundwater potential. The study identifies five distinct groundwater potential categories based on area coverage:very low (242.44 km2), low (147.52 km2), medium (241.72 km2), high (26.35 km2), and very high (18.51 km2). The predominant factors influencing the groundwater potentiality are top soil thickness, pediment as well as pediplain (shallow to moderately weathered), lithology (charnockite and fissile hornblende biotite gneiss), slope type (gentle), and rainfall (high). A very good correlation between the groundwater potential zones and the well yield aided in validation of the above findings.