Characterization of hydrogeological conditions and interactions between surface water, irrigation water, and groundwater in the Senegal River delta

Abstract

The Senegal River delta is located in north-west Senegal, and is a relatively humid region in an otherwise semi-arid zone, thanks to the presence of the Senegal River and it's various tributaries and distributaries. The groundwater of the shallow Quaternary and alluvlal aquifers has been heavily salinized due to cyclical marine invasions over the course of recent geological history. Salt in the shallow aquifer is an issue because of the facility in which dissolved solids can reach the surface and precipitate in the top meters of soils, degrading the land. These lands are of extreme importance to the country for agricultural activity. In the interest of reaching a state of food self-sufficiency, and under pressure of a growing population, the delta has been built up and organized to support irrigated agriculture of multiple crop types. Among these efforts include the construction of the Diama anti-sel dam at the end of the 1980's. Despite these efforts, the soil and the groundwater of the shallow aquifer is still saline. The following project is a hydrogeological study of the salinization issue in the delta. Particular interests were to quantify the extent of groundwater and surface water interactions, in the objective of bringing into evidence a fresh water recharge from the river into the groundwater. After a complete contextual literature study, including integration of historical data, the site setup was outlined, and geophysical and geochemical data were collected for analysis. Results were provided from electrical resistivity tomography, electromagnetics, hydrodynamics, and hydrochemical analyses. In the final discussion, suggestions for future study were provided.