Self-Potential Survey for Hydrogeological Mapping in Anambra State

This study applies self-potential surveying to map hydrogeological features including groundwater flow paths, seepage zones, and permeable fault structures in parts of Anambra State, South East Nigeria. The self-potential method measures naturally occurring electrochemical potentials generated by electrokinetic flow, chemical diffusion, and thermoelectric effects in the subsurface, providing information about fluid movement and redox chemistry that complements conventional resistivity measurements. In the sedimentary terrain of Anambra State, SP anomalies have been shown to correlate with productive aquifer zones and groundwater discharge points. This study measures self-potential at 245 stations on a 20 by 20 metre grid in Awka South and Aguata local government areas using porous pot non-polarisable electrodes connected to a high-impedance digital voltmeter. Profiles are also measured across identified lineaments in the area. SP data are corrected for topographic effects and plotted as plan maps and profiles. Correlation with existing borehole data is used for verification. Findings reveal negative SP anomalies of 80 to 160 millivolts associated with observed spring seepage and borehole sites of known high productivity, consistent with electrokinetic current flow in the direction of groundwater movement. Two previously unmapped groundwater pathways are identified along northeast-trending drainage lineaments. A positive SP halo around a known industrial site indicates chemical diffusion related to industrial waste leachate. The study recommends SP surveying as a low-cost complement to resistivity methods for groundwater exploration in Anambra's shallow aquifer systems.

Keywords: self-potential, hydrogeological mapping, groundwater flow, Anambra State, electrokinetic.