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.

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.

The Chari-Baguirmi aquifer, located East of Lake Chad, is the main source of water in this region. The groundwater piezometry is marked by a large depression. The work presented here aims to understand the development of this depression. The approach is based on a sedimentological study coupled to a hydrogeochemical study of the groundwater. The sedimentological analysis revealed the grain size heterogeneity of the different layers. Clay mineralogy showed that the deposition of sediments takes place from the periphery to the center of the depression. This sedimentation mode suggests the existence of a morphological cuvette to which sediments are driven by the transport agent. We deduced the existence of a "structural" depression unlike the common assumption of an origin due to accentuated evaporation of the groundwater over the depression area. The combined study of chloride and oxygen-18 has shown that the area between Lake Chad and the piezometric depression is a special evaporation zone. This means that the process of evaporation of groundwater does not occur mainly in the center of the depression. The first results of this work provide new insights into the functioning of this important aquifer system and the establishment of the large Chari Baguirmi piezometric depression.