Integrated geophysical and lithological analysis of a semi-arid karst basin for sustainable water management: Wadi Zouzfana (South-Western Algeria)

Assessment of hydrogeophysical delineation of groundwater zones using vertical electrical sounding (VES) in Jeypore Block, Koraput District, Odisha

Groundwater occurrence in hard-rock terrains is complex and spatially heterogeneous, controlled by weathered and fractured zones with limited surface expression. This research integrates Vertical Electrical Sounding (VES) with remote sensing, GIS and Analytical Hierarchy Process (AHP) for groundwater potential mapping of Jeypore Block, Koraput District, Odisha. This area is underlain by Eastern Ghats Mobile Belt rocks such as khondalites, charnockites, and granite gneisses. Fifteen VES surveys using Schlumberger configuration were conducted across the study area, with electrode spreads up to 800 m. Resistivity data were interpreted using IPI2WIN software, producing one-dimensional resistivity models and Dar-Zarrouk parameters. Subsurface profiling revealed distinct lithological layers consisting of topsoil, laterite, sandstone, weathered/fractured granite, and compact bedrock. Layer thicknesses ranged from 0.6 to 20.4 m in the first layer to 99.5 m in the third layer. Iso-resistivity maps generated using Surfer-25 showed significant lateral heterogeneity. Low-resistivity zones (2.6–105.2 Ωm) indicated saturated formations, whereas high-resistivity values (> 150 Ωm) represented compact basement rocks. Curve-type analysis identified predominantly AAA-type curves, which indicate increasing resistivity with depth. HA-type curves observed at two locations suggested the presence of conductive, water-saturated layers favourable for aquifer development. VES-derived parameters were integrated with twelve geospatial thematic layers, including geology, geomorphology, soil, NDVI, lineament density, drainage density, rainfall, slope, physiography, land use, groundwater fluctuation, and hydrogeology, using the AHP framework. The consistency ratio of the model was 2.36%, indicating reliable thematic weighting. Validation via pumping tests and ROC analysis (AUC = 0.86) confirmed model reliability. This approach offers a scientifically robust framework for sustainable groundwater management in structurally complex hard-rock terrains.

VES-based characterization of lithological heterogeneity for potential groundwater development in the quaternary floodplain of Jashore Sadar, Bangladesh

Subsurface geology in deltaic floodplains is highly heterogeneous, strongly influencing groundwater development. In response to growing groundwater stress and the need for potential management, this study investigates the capability of vertical electrical sounding (VES) to characterize lithological variability and infer hydrostratigraphic conditions within the active floodplain of the Quaternary deposits of Jashore, Bangladesh. A total of 18 VES surveys were conducted using the Schlumberger array with investigation depths of 90–150 m. One-dimensional inversion modeling using IX1D was validated against nearby borehole logs, showing strong agreement for layer depth and thickness (R² > 0.95) and approximately 75% agreement in lithological classification. The results show five geoelectric layers with resistivity values ranging from 6 to 60 Ωm, corresponding to topsoil, clay, silty clay, and sandy lithologies, indicating considerable lateral and vertical heterogeneity across the floodplain. Furthermore, geo-electric cross-sections indicate that shallow or thick sandy units are concentrated around VES-3–7, 9–11, and 14–17, whereas clay-rich deposits dominate VES-1, 12, 13, and 18. In particular, the sandy layers characterized by relatively high resistivity (36–60 Ωm) and substantial thickness (32.35–94 m) are interpreted as potential aquifer zones, while the overlying clay and silty clay units suggest as confining to semi-confining layers. Moreover, the absence of very low resistivity signatures suggests limited saline water intrusion within the investigated depth range. Although hydrochemical and pumping-test data are still required for confirmation, our study develops a conceptual framework of lithological heterogeneity using VES for potential groundwater management applicable for similar floodplain environments.

Assessment of Borehole Failure in the Global South: Integrated Hydrogeological and Geophysical Evidence from Gombe Metropolis, Northeastern Nigeria

Groundwater underpins domestic water supply across much of the Global South, yet chronic borehole failure continues to undermine investment in water-supply infrastructure, particularly in geologically heterogeneous sedimentary basins where site selection is rarely constrained by integrated subsurface data. This study presents an integrated hydrogeological, geophysical, and statistical assessment of groundwater occurrence and borehole performance in Gombe Metropolis, northeastern Nigeria, a rapidly urbanizing city of approximately 450,000 people situated within the Gongola Sub-basin of the Upper Benue Trough. A compiled inventory of 71 borehole records (depth, functional status, and, where available, yield) was cross-referenced against 23 Vertical Electrical Sounding (VES) stations acquired using the Schlumberger configuration, in order to constrain otherwise non-unique geoelectric interpretation with authentic subsurface ground-truth. Complete depth and functional-status data were available for 58 of the 71 boreholes (35 functioning, 23 not functioning), forming the basis for formal statistical testing, while a richly documented subset of 32 boreholes (24 with individually reported depths) supported a ward-level qualitative analysis of failure mechanisms. Non-functional boreholes cluster in the wards of Bolari and Jakada Fari at shallow-to-intermediate depths, where thick sequences of the Pindiga (Fika) Shale, ironstone intercalations within the middle member of the Gombe Formation, and structurally attenuated stratigraphy act as hydrogeological barriers; however, a Mann–Whitney U test across the full 58-record subset found that borehole depth alone did not significantly distinguish functioning (mean 86.6 ± 29.3 m) from non-functioning boreholes (mean 72.0 ± 31.0 m; U = 505.0, p = 0.105, rank-biserial r = 0.255). Across the 23 VES stations, groundwater potential was descriptively associated with aquifer lithology (Cramér's V = 0.423) though this did not reach significance in a Fisher–Freeman–Halton exact test (p = 0.458) given the small, sparse sample; clean, fine-grained sand and sandstone units nonetheless hosted the majority of highpotential occurrences, whereas silty and clay-dominated facies were predominantly moderate to poor except where deeply confined (> 135 m). In contrast, aquiferous depth was strongly and significantly correlated with VES-derived groundwater-potential class (Spearman ρ = 0.682, p < 0.001; Kruskal–Wallis H (2) = 12.63, p = 0.002). A shallow functional outlier and a faultassociated deep success zone near Pantami confirm that depth alone is an incomplete predictor of borehole outcome. Taken together, the statistical and geological evidence indicates that borehole failure in Gombe Metropolis is governed jointly by aquiferous depth and lithological confinement rather than by depth in isolation, and that borehole ground-truthing is indispensable for resolving the inherent ambiguity of VES interpretation in structurally complex sedimentary terrains. The findings provide an evidence-based basis for depth-targeted drilling, ward-specific development planning, and groundwater protection policy in Gombe and analogous basins across the Global South.

Integrated evaluation and sustainable development implications of a Cambrian-Ordovician karst geothermal reservoir in the southern Fenwei Graben system, North China

Low-to medium-temperature geothermal systems are important geological energy resources for clean heating and carbon-emission reduction, but their development in karst carbonate reservoirs is commonly limited by strong reservoir heterogeneity, uncertain groundwater circulation pathways, and risks associated with production-reinjection imbalance. In intracontinental rift basins of North China, deeply buried Cambrian-Ordovician carbonate reservoirs provide promising geothermal targets; however, the links among multi-stage reservoir formation, heat accumulation, well-group productivity and sustainable development remain insufficiently constrained. Taking the Linyi geothermal field in the southern Fenwei Graben System as a representative case, this study combines balanced-section restoration with outcrop and well-section observations, temperature logs, a newly compiled stratified production profiles from 12 wells and resource evaluation. Shallow-marine carbonate deposition provided the basic reservoir framework, whereas post-Ordovician exposure formed weathering-crust karst and unconformity-related storage. Later structural modification and Cenozoic fault subsidence adjusted burial depth, fracture connectivity and groundwater pathways. The effective reservoir is mainly developed in the Upper and Lower Majiagou formations, while the Yeli and Zhangxia-Xuzhuang formations contribute locally. Faults, unconformities and karst-fracture zones jointly control recharge, flow and heat accumulation, and may locally enhance vertical connectivity. Resource calculations indicate a recoverable geothermal resource of 1.33 × 10 9 GJ and annual usable heat of 1.67 × 10 7 GJ/a. These findings provide a geological basis for sustainable development of karst geothermal resources in the southern Fenwei Graben System and highlight the need to verify reinjection safety and long-term production–reinjection balance through tracer tests, reinjection tests and long-term monitoring of temperature, pressure, flow rate and hydrochemistry.

Litho-tectonic and geomorphological controls on the hydrogeochemistry of selected springs in the upstream Nekor watershed, northern Morocco

Lithological schematization of the Karnali fluvial fan (Nepal’s Terai Arc Landscape) using electrical resistivity tomography as a basis for hydrogeological investigations

In the Nepalese and Indian Terai Arc Landscape (TAL), protected nature areas are supported by groundwater systems that have remained largely understudied. This study schematizes the lithology of the Karnali fluvial fan located in the Bardia district (Nepal) as a basis for future hydrogeological investigations. Inversion results of 2D electrical resistivity tomography (ERT) profiles at 21 locations were interpreted by comparing with the local borehole lithology and regional geophysical studies. Multiple lithological cross-sections were prepared to develop a 3D lithological model spanning the fan, and the adjacent Bardia National Park up to the Babai River in the east. Sediment resistivities found were in the range of 8–6000 Ω m. Resistivity less than 40 Ω m was identified as clay, 40–80 Ω m represented silt and fine sand, 80–400 Ω m identified as fine to coarse sand and resistivities higher than 400 Ω m were interpreted as coarse sand, gravel and boulders. A coarse sand-gravelly layer is present at the fan apex and along the foot of the Himalayas in the north that functions as a recharge area and aquifer. The central part of the fan has sandy layers which transition to fine sand and silt layers in the distal south and southeast. Clay layers locally create confining conditions, within the sand and silt dominated areas. These findings on subsurface lithology provide valuable insights for the groundwater systems which sustain ecohydrological processes relevant to the protected ecosystem and fills a critical knowledge gap on regional hydrogeology of the TAL.