Accessing the accuracy of modified Schlumberger (Hummel) array of vertical electrical sounding: a pivotal to groundwater exploration

Space constraints encountered in areas with well-developed housing layouts impede geophysical exploration for groundwater. The study aims to evaluate the effectiveness of the modified Hummel array in groundwater exploration. Thirty-two vertical electrical sounding (VES) data were obtained using both the full and half Hummel and Schlumberger arrays on a migmatite gneiss, revealing its applicability in a complex geology. The data were processed by curve matching and computer iteration. The curve types (H, KH, and QH) and geoelectric sequences inferred from the arrays showed similar layer distributions. The correlated raw data and geoelectric parameters generated moderate to strong coefficients (0.5224-0.9999), indicating a high degree of similarity. The T-values (>2) confirmed the reliability of the coefficients used as predictors. The closeness of data around 1:1 line revealed half Hummel to be a better substitute for Schlumberger, especially in built-up areas where mirror electrode spread is not achievable due to space constraints.