2D and 2.5D modeling of the piezometric surface of the Pan-African basement aquifers in the Sudano-Sahelian zone of Cameroon using the Kriging method

This study models the piezometric surface of Pan-African basement aquifers in the Sudano-Sahelian zone of Cameroon using a combined 2D and 2.5D geostatistical approach based on kriging. The integrated analysis of the thalweg surface (Zr) and the piezometric surface (Zp) provides insight into groundwater flow dynamics in a fractured basement context. Results indicate a preferential groundwater flow direction from southwest to northeast; both regional topography and underlying structural features influence this. The comparison between Zp and Zr reveals critical hydrogeological patterns: areas where Zp closely matches Zr (ΔZ < 5 m) indicate discharge zones or resurgence areas, typically near thalwegs. In contrast, sectors with large Zp–Zr differentials (> 40 m) represent deep recharge or long-term storage zones. For instance, in upstream areas, Zp reaches 680 m while Zr remains around 630 m, yielding saturated thicknesses exceeding 50 m. The maximum observed piezometric gradient is approximately 26%, confirming sharp vertical transitions linked to structural controls. A strong empirical correlation (Rp² = 0.9961) between Zp, Zr, and the digital elevation model (DEM) enabled the formulation of a predictive equation for estimating theoretical piezometric levels. The kriged 2.5D surface further reveals local discontinuities, interpreted as fractures or lithological contacts affecting vertical and lateral flows. This modeling framework represents a robust decision-support tool for sustainable groundwater resource management. It helps in identifying optimal drilling targets in structurally favorable zones and helps monitor vulnerable areas at risk of seasonal depletion or contamination. The approach strengthens hydrogeological planning in tropical basement environments increasingly impacted by anthropogenic and climatic pressures.