Integrated geophysical and hydrochemical assessment of groundwater potential and its suitability in the Vikasnagar block of Dehradun district, Uttarakhand, Northern India

An integrated geophysical and hydrochemical investigation was carried out to assess groundwater potential and its suitability in Vikasnagar block of Uttarakhand, Northern India. Direct current (DC) resistivity sounding using Schlumberger configuration was combined with borehole lithology and groundwater chemistry to delineate aquifer geometry and evaluate groundwater quality. A total of twenty vertical electrical soundings (VES), with the current electrode separations (AB) ranging from 400 to 800 m, were conducted to characterize subsurface aquifer disposition. Two borehole lithologs were used to constrain and validate the interpreted geoelectrical models. Hydrochemical analysis of fourteen groundwater samples collected from hand pumps was performed to assess suitability of drinking and irrigation. The VES interpretation has delineated 6–9 geoelectrical layers up to a depth of ~ 136.5 m and it has revealed a heterogeneous subsurface comprising alluvium, saturated clayey horizons, and compact hard rock formations. Aquifer resistivity values range from 23.7 to 257.5 Ω-m, with thicknesses between 17.2 and 68.1 m and depth extending up to ~ 115, indicating favorable groundwater-bearing zones mainly associated with low to medium resistivity alluvial formations. Hydrochemical results show that all samples fall within the BIS and WHO permissible limits, with TDS < 500 mg/L, neutral to slightly alkaline in pH, and acceptable hardness. Irrigation quality assessment indicates all samples in excellent to good categories. A strong inverse relationship between aquifer resistivity and electrical conductivity (EC) further confirms the constancy between geophysical and hydrochemical datasets. To enhance the quantitative reliability of the integrated geophysical-hydrochemical interpretation, uncertainty and stochastic analyses were applied to aquifer resistivity, thickness, and EC values of groundwater. It indicates that low to medium resistivity aquifer zones have higher probability of groundwater occurrence and acceptable quality, while spatial variability shows the influence of lithology, clay content, and saturation conditions. This study demonstrates the effeteness of integrated geophysical-hydrochemical approaches for reliable groundwater potential and quality assessment.