GPR imaging of a sand dune aquifer: A case study in the niayes ecoregion of Tanma, Senegal

Local agriculture in Senegal is dependent on truck farming, which is concentrated in the narrow interdunal zone of peat deposits, called “niayes”. The viability of the niayes significantly depends on the sand dune aquifer, as a consequence of recent over-pumping. In the present paper, we discuss the ability of GPR to locate the water table, in a highly vegetated interdunal area which includes peat fields, as well as internal dips, which were shown to be complex. Three profiles determined in the interdunal zone have been associated with several boreholes. Analysis of the radargrams clearly shows that 1) the presence of dense vegetation is not a penalising factor; 2) phase inversion in the measured signal could be useful in distinguishing between the presence of a significant water contrast, and that of a strong stratigraphic reflector; 3) in sand dunes, the electromagnetic contrast resulting from a wetting front is likely to be of the same order as that of the water table. The outcome of this study may provide clues to the characterisation and management of water resources in niayes area.