Application of statistical and Hydrochemical methods to the analysis of the groundwater in the Guiglo-Duekoué area (Western area of Ivory Coast)

Several hydrogeological studies have been conducted throughout the Ivory Coast for a better (quantitative and qualitative) assessment of groundwater resources. The results obtained in these studies are extremely encouraging and contributed in particular to a better understanding of the hydrogeochemistry of groundwater. However, despite these considerable achievements, efforts still need to be made. In the western region, which is now the new Cocoa belt, such studies are virtually nonexistent. Therefore, the present study was undertaken in order to contribute to the knowledge of the hydrogeochemistry of aquifers in the West of Ivory Coast. This study was conducted specifically in the Guiglo-Duekoué area which is located between latitudes 7°00 and 7°42’ North and longitudes 6°28’ and 6°50’ West. The objective of this study is the hydrogeochemical characterization of groundwater for the understanding of its mineralization. This work was conducted from the results of the analyses of physical and chemical parameters of water and relied on a sample of 48 drillings. The methodology used is based on a combination consisting of statistical methods (Normalized Principal Component Analysis and Ascending Hierarchical Classification) and hydrochemical (Index of base exchange). The results of statistical analysis have identified two main mechanisms that are responsible for the evolution of the mineralization of the groundwater of the Guiglo-Duekoué area. The first mechanism is the phenomenon of mineralization coupled with the residence time which reveals the hydrolysis of silicates after the infiltration of water enriched in CO₂ from the ground. The second mechanism is the oxidation-reduction phenomenon, related to turbidity, to the concentrations of iron and manganese. The index hydrochemical study showed that the third phenomenon responsible for the mineralization of groundwater is the ion exchange between water and rock. These results contribute to a better understanding of hydrogeochemical properties of the groundwater of the crystalline basement of Archean and SASCA areas of Ivory Coast.