Water supply in the Saloum area is provided by the groundwater in the sandy-clay formations of the Continental Terminal. The presence of hypersaline waters from the Saloum River in the north and the ocean in the west, climate change and population growth are threatening groundwater resources, hence the need for a better understanding of the aquifer system. The aim of this work is to establish a hydrodynamic model that can reproduce the behaviour of flows by identifying the main recharge and evaporation mechanisms and estimating the hydrodynamic properties. The heterogeneity of the geological formation is at the root of a very large variation in the hydraulic parameters. This heterogeneity and the very limited uncertainty in the data justify opting for a stochastic modelling approach. The modelling is carried out under steady state conditions with imposed loads in order to quantify the natural flows passing through the aquifer and to understand the distribution of hydrodynamic parameters in order to reconstruct the piezometry. The probability densities for the values of permeability and recharge obtained indicate a high sensitivity of the simulations to these two parameters. The hydraulic conductivity values oscillate between 10-2 and 10-5 m.s-1 and are identical to those obtained by test pumping. The overall average balance shows a perfect balance between inflow and outflow. The average annual recharge of 13.98 mm is provided mainly by rainwater, and evapotranspiration is 13.65 mm. The model, which is deemed acceptable under steady-state conditions, will serve as the basis for modelling saline intrusion.

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.