Evaluation of Aquifer Vulnerability Using Geo-Electrical Surveys: Case Study of Obbo Payam, South Sudan

Groundwater resources in data-scarce regions of Sub-Saharan Africa face increasing pressure from overexploitation and contamination. Assessing aquifer vulnerability is therefore critical for sustainable management. This study evaluates aquifer protective capacity of overburden materials in Obbo Payam, South Sudan using Vertical Electrical Sounding (VES) and Total Longitudinal Conductance (TLC) as proxy indicator. A total of 14 VES points were analyzed using the Schlumberger configuration. Interpretation was conducted using IP2Win software, and aquifer protective capacity was inferred from and Total Longitudinal Conductance (TLC) values. The results categorized into five curve types (H, QH, A, K, and HK) with three layers models dominating (79%) and four layer models (21%). The results of TLC reveal significant spatial variability: 14% of the area exhibit excellent protection, 29% are classified as very good to good, 21% as moderate and 36% as weak to poor. The zones with high TLC values correspond to thicker clay-rich layers that enhance natural infiltration potential, whereas areas with low TLC values are more vulnerable to contamination. This study demonstrates that combining VES TLC analysis provides a cost-effective and practical approach for delineating aquifer vulnerability in regions lacking detailed hydrogeological data. The findings support the prioritization of groundwater protection measures and contribute to broader goals such as Sustainable Development Goal 6 on clean water and sanitation.