Soil Texture as a Determinant of Groundwater Recharge Potential in Semi-arid Hard Rock Terrain of Yadgir District, Karnataka, India

Abstract

Aims: To determine whether the spatial distribution of soil textural classes across the Yadgir and Gurmitkal blocks can predict groundwater recharge conditions observed at borewell sites, using an infiltration-capacity-based suitability ranking. Study Design: Spatial soil-texture mapping combined with a five-tier recharge suitability ranking, cross-validated against field-observed borewell hydrogeological parameters. Place and Duration of Study: Yadgir and Gurmitkal blocks, Yadgir District, Karnataka, India, covering 1,711.6 sq. km and 45 target villages; geohydrological data collected under the Kalike programme, with rainfall records spanning 1995–2024. Methodology: Soil texture governs infiltration rate, water-holding capacity, and porosity. These three properties directly control the volume of rainwater reaching the saturated zone in hard rock aquifers. Despite its recognised importance, soil texture has seldom been isolated as the sole explanatory variable in groundwater recharge potential assessments for the crystalline basement terrain of the Deccan Plateau. This study examines the spatial distribution of twelve soil textural classes across 1,711.6 square kilometres of the Yadgir and Gurmitkal blocks in the Yadgir District of Karnataka, India. It uses National Bureau of Soil Survey and Land Use Planning maps refined with IRS Resource SAT 2 LISS IV 5.8 m imagery. Results: Mapped soil classes range from clay (167.65 sq. km) to clay loam (405.57 sq. km). Loamy sand is the most extensive class, covering 460.26 sq. km (26.9%). Sandy loam covers 327.31 square kilometres, and sand spans 75.85 sq. km. Minor occurrences include gravelly sand at 1.16 square kilometres and gravelly sandy loam at 8.38 square kilometres. A textural-class-based recharge suitability ranking is applied to the area. This ranking is grounded in published infiltration capacity hierarchies for Indian semi-arid soils. It is also cross-validated against hydrogeological observations from 247 borewells. Villages underlain by loamy sand and sandy loam show shallower first water strike depths at 30 to 60 feet below ground level. Their static water levels range from 11 to 40 feet below ground level. In contrast, clay-dominated areas have first water strikes and static water levels deeper than 60 feet below ground level. This confirms the field-level correspondence between coarser-textured soils and better recharge conditions. These findings have direct implications for prioritising artificial recharge structures and borewell siting in the selected intervention villages. Conclusion: Soil texture, mapped at NBSS and LUP resolution and ranked by infiltration capacity, is a reliable, low-cost predictor of groundwater recharge potential in hard-rock, semi-arid terrain and can directly guide managed aquifer recharge structure siting.