Crystalline basement rock aquifers underlie more than 20% of the earth’s surface. However, owing to an inadequate understanding of geological structures, it is challenging to locate the groundwater resources in crystalline hard rock terranes. In these terranes, faults, fractures, and shear zones play an important role in bedrock weathering and ultimately groundwater storage. This study integrates important geological structures with 2D high-resolution subsurface resistivity images in understanding the factors that influenced bedrock weathering and groundwater. The results reveal the variability of weathered zone depth in different structural zones (Zone-I to Zone-IV). This is due to the presence of foliations, fractures, and faults. A thicker weathered zone develops when a fracture/fault overprints a pre-existing planar pervasive structure like foliations (Zone-II) as compared to zones only with faults/fractures (Zone-III). Further, the transmissivity of boreholes also shows relatively higher in Zone-II than Zone-III, which implies a good pact between different structural features and possible groundwater storage. The study also demonstrates the role of paleostress and different tectonic structures influencing the depth of the “Critical Zone”. While the geology may vary for different structural terranes, the approach presented in this paper can be readily adopted in mapping bedrock weathering and groundwater resources in crystalline basement terranes globally.

In North Gujarat, local communities depend on the Precambrian basement aquifers for their primary source of water supply. The increasing demand for potable water puts stress on exploring for groundwater from less reliable sources of basement rocks. The main objective is to map groundwater potential zones (GWPZs) in water-scarce Precambrian terranes using integrated multi-criteria analysis (analytical hierarchy process and geospatial techniques). The output of the GWPZ map was grouped into six different categories. The results show that very high and high groundwater potentials extend over areas of 4.29% and 12.86%, respectively. The kappa index method was used for validation and showed an effective result between collected water-level data with calculated GWPZ. It shows 83.3% accuracy for very high, 85.7% for high and 90.1% for moderate GWPZs. The study shows promise and highlights that such an integrated analysis is reliable and can be applied anywhere with a similar set-up for groundwater prospecting and management.

Considering water as a limiting factor for socio-economic development, especially in arid/semi-arid regions, both scientific communities and policymakers are interested in groundwater recharge-related data. India is fast moving toward a crisis of groundwater due to intense abstraction and contamination. There is a lack of understanding regarding the occurrence, movement, and behaviors of groundwater in a fractured basement terrane. Therefore, integrated environmental isotopes (δ¹⁸O, δ²H, and ³H) and hydrogeochemical studies have been used to understand the recharge processes and geochemical evolution of groundwater in the fractured basement terranes of Gujarat, NW India. Our results show that the relative abundance of major cations and anions in the study basin are Ca²⁺ > Na⁺ > Mg²⁺ > K⁺ and HCO₃⁻ > Cl⁻ > SO₄²⁻ > NO₃⁻, respectively. This suggests that the chemical weathering of silicate minerals influences the groundwater chemistry in the aquifer system. A change in hydrochemical facies from Ca-HCO₃ to Na-Mg-Ca-Cl. HCO₃ has been identified from the recharge to discharge areas. Along the groundwater flow direction, the presence of chemical constituents with different concentrations demonstrates that the various geochemical mechanisms are responsible for this geochemical evolution. Furthermore, the chemical composition of groundwater also reflects that the groundwater has interacted with distinct rock types (granites/granulites). The stable isotopes (δ¹⁸O and δ²H) of groundwater reveal that the local precipitation is the main source of recharge. However, the groundwater recharge is affected by the evaporation process due to different geological conditions irrespective of topographical differences in the study area. The tritium (³H) content of groundwater suggests that the aquifer is mainly recharged by modern rainfall events. Thus, in semi-arid regions, the geology, weathering, and geologic structures have a significant role in bringing chemical changes in groundwater and smoothening the recharge process. The findings of this study will prove vital for the decision-makers or policymakers to take appropriate measures to design water budgets as well as water management plans more sustainably.

Despite being a biodiversity hotspot, the Mahanadi delta is facing groundwater salinization as one of the main environmental threats in the recent past. Hence, this study attempts to understand the dynamics of groundwater and its sustainable management options through numerical simulation in the Jagatsinghpur deltaic region. The result shows that groundwater in the study area is extensively abstracted for agricultural activities, which also causes the depletion of groundwater levels. The hydraulic head value varies from 0.7 to 15 m above mean sea level (MSL) with an average head of 6 m in this low-lying coastal region. The horizontal hydraulic conductivity and the specific yield values in the area are found to vary from 40 to 45 m/day and 0.05 to 0.07, respectively. The study area has been calibrated for two years (2004–2005) by using these parameters, followed by the validation of four years (2006–2009). The calibrated numerical model is used to evaluate the net recharge and groundwater balance in this study area. The interaction between the river and coastal unconfined aquifer system responds differently in different seasons. The net groundwater recharge to the coastal aquifer has been estimated and varies from 247.89 to 262.63 million cubic meters (MCM) in the year 2006–2007. The model further indicates a net outflow of 8.92–9.64 MCM of groundwater into the Bay of Bengal. Further, the outflow to the sea is preventing the seawater ingress into the shallow coastal aquifer system.