Hydrogeological characterization of the effutu municipality: a geophysical and geostatistical – based development of sustainable drilling-depth framework

Abstract This study characterizes the hydrogeological profile of the Effutu Municipality of Ghana to support evidence-based groundwater development in an area experiencing persistent borehole and well failures. The objective of the study was to evaluate groundwater availability, estimate aquifer depths, and develop drilling-depth guidance capable of sustaining groundwater abstraction. Based on Vertical Electrical Sounding (VES) data from 16 locations using the Schlumberger array, the study uniquely integrates VES-based aquifer depths and geostatistical modeling for validation using measured water levels to generate a drilling depth framework. Ordinary least squares (OLS) regression was employed to quantify the extent to which variations in measured groundwater levels from 27 wells and 4 boreholes are explained by VES-inferred depths of geological saturation. The OLS regression found a significant positive relationship between VES-inferred saturations and measured groundwater levels (R 2 = 0.41, p < 0.001). Modeling of geoelectrical layers’ resistivity and thickness using Inverse Distance Weighted (IDW) interpolation revealed predominantly shallow aquifers with spatial variations in depths ranging from 1.5 m to about 20 m. Spatial autocorrelation identified significant clustering of groundwater levels (Moran’s I = 1.14, p = 0.0006), suggesting substantial groundwater endowment across the Municipality. However, spatial variation in aquifer depths indicates that borehole success in the Municipality is strongly dependent on drilling depth relative to depths of permanent saturation. These findings indicate that groundwater development outcomes in the Effutu Municipality are best optimized when drilling decisions are informed by site-specific hydrogeological conditions rather than relying solely on mechanical or operational considerations.