Soil Degradation in the Senegal Lower Valley

The Senegal River is regulated by two dams, the Diama anti-salt dam constructed in 1986, close to the river mouth (Fig. 1), to prevent marine intrusions during high tides, and the Mantanali reservoir dam that was impounded two years later in Mali. Since then, there has been a spectacular development of irrigated agriculture in the valley. The initial plan for development of the Senegal River valley envisaged a potential of at least 250,000 ha, which could be increased to 375,000 ha, mainly in the two countries, Senegal and Mauritania. This intensification of agriculture and the increase in irrigated areas has disrupted the existing environmental balance. It is therefore important to determine whether they have caused soil degradation, or simply offered a new framework for the development and exploration of the Senegal middle valley. Impact studies prior to development are generally insufficient to understand the environment and the complexity of its functioning. As will be shown in this study, recent pedogenetical processes in the Senegal River valley have led to soil diversity and salinity distribution. The first objective is to illustrate the mechanisms that dominated this environment until the commissioning of the two dams. In a second step, we will present the evolution