In the Samba Dia area, located in central western Senegal, the Quaternary aquifer is the only one exploited for the population’s drinking water needs. The main objective of this study is to update and analyze the hydrochemical data of this aquifer. Physicochemical analyses were carried out on 36 water samples to characterize the groundwater in the aquifer and explain the phenomena behind the mineralization of this water. Interpretation of the hydrochemical data was done using the Piper diagram, multivariate analysis (Factor analysis and Hierarchal cluster analysis (HAC)), base exchange index and Na vs Cl, HCO3 vs Ca and (Na-Cl)] vs [(Ca+Mg) - (HC03+S04)] relationships. Water-rock interaction (rock dissolution, base exchange processes) is the dominant mechanism for ion acquisition in the groundwater of this aquifer. The other mechanism is related to water inputs by surface infiltration and intrusion of marine and brackish water. The results of the hydrochemical study show that the chemical species that control water salinization are ions Cl, Na, SO4, Mg, Ca and HCO3.The hydrochemical facies observed for the groundwater samples are Na-Cl (70%), CaCl2 (12.22%) and mixed.

This study intends to see the temporal and spatial evolution of groundwater salinization at the northern and western zone of the CT aquifer in the Sine-Gambie region (Senegal). To do this, a hydrochemical study was conducted in 2015 and compared with previous studies (2000 and 2012). This study is essentially based on the two parameters, electrical conductivity and chloride content. The results obtained show that the evolution of salinity observed in these areas is explained by a contamination of the groundwater by the waters from the Saloum River and the sea. The comparison of groundwater electrical conductivity maps showed a salinity increase between 2000 and 2015; with a salinization phenomenon which increases toward inland in phase with chloride levels that doubled in some wells. The study also shows that several calcium bicarbonate facies have evolved to calcium chloride facies, and calcium chloride facies to chloride sodium facies.