Chemical signature and structural study of a Madingou hydrokarst system, southwest of the Republic of Congo.

 

The aim of this study is to understand the relationships between surface and underground flows of Kibounda karstic system, near Madingou town, in the southwest of the Republic of Congo. This karst system developed within the carbonated formations of the Neoproterozoic Schisto-Calcaire Group, and is characterized by a distinctive landscape featuring cone and pinnacle reliefs typical of tropical karst terrain. Surface flows appear rare and are influenced by seasonal rhythms. Structural studies and chemical analyses of the water were carried out in order to understand how the network operates according to seasonal variations.

Surface and groundwater samples were collected, and major ions were analysed to understand the geochemical processes controlling the water chemistry in Kibounda. High concentrations of Ca, Mg, and HCO₃ indicate the dissolution of limestone and dolomite rocks. The observed SiO₂ concentrations in these waters suggest the widespread presence of silicates in the soils and rocks of the carbonate reservoir. Significant concentrations of sulfates in the rivers would indicate contamination of the water by anthropogenic activities. Other major ions are present in marginal concentrations, with Sr detected in trace amounts.

Structural measurements realized at key sites in the area show two dominant fracture orientations, NE-SW and NW-SE, along which water flows preferentially. These fractures are the fundamental drivers in the genesis of multiple karstic sites in the region.

The study determined the hydraulic connections between different sites following on their hydrochemical characteristics. It provides the information needed to understand the hydrochemical functioning of the Kibounda karstic system, contributing to the sustainable management of water resources of this area.

Keywords: Kibounda, Hydrokarst System, hydrochemical characteristics, Structural control, Congo Republic.