Three-Dimensional Electrical Resistivity Tomography for Sustainable Groundwater Mapping in Abéché Basin Chad

Abstract Crystalline bedrock aquifers are vital groundwater resources in semi-arid regions like the Sahel, where water scarcity exacerbated by climate variability and population growth poses a fundamental challenge to achieving Sustainable Development Goal 6 targets for clean water and sanitation. In the Abéché Basin Chad these aquifers are critical for over 30 million people yet their heterogeneity challenges traditional exploration methods which yield only a 40% success rate hindering sustainable development efforts. This study applied 2D and 3D electrical resistivity tomography ERT to map aquifer geometry and recharge mechanisms in an urban semi-arid setting addressing a key knowledge gap for sustainable groundwater management. Using a Syscal Pro 64-electrode system we acquired 20 2D profiles and seven 3D blocks across ten neighborhoods. Validation against eight boreholes achieved a 75% success rate versus 40% for traditional methods with yields up to 43 m³/h. A strong negative correlation (ρ = -0.90, p = 0.002) between resistivity and yield was found. By optimizing borehole siting and reducing exploration costs this study provides a practical framework for sustainable groundwater exploration. The 75% drilling success rate, compared to 40% for traditional methods, enhances water access (SDG 6.1), promotes efficient resource use (SDG 6.4), strengthens climate resilience (SDG 13.1), and supports poverty reduction (SDG 1.5) by enabling cost-effective water infrastructure development. These findings offer a replicable model for achieving water security and fostering socio-economic development in vulnerable Sahelian communities, thereby contributing directly to broader socio-economic development.