Multi-approach characterization of groundwater for irrigated agriculture in southwest Burkina Faso

This study aims at contributing to the sustainable management of groundwater emergences located in the Sindou Peaks irrigated area. The choice of this study area is due, on the one hand, to its geological context located between the sedimentary and crystalline rocks and, on the other hand to its economic interest. The study focused on understanding the groundwater emergences mechanism and their origin which are currently poorly known. To this end, geophysical investigations such as very low frequency electromagnetic (VLF) and self-potential surveys were carried out. The electromagnetic survey pro-vided a 2D image of the subsoil conductivity and highlighted the fault zones. Self-potential surveys confirmed the effec-tiveness of groundwater emergence through the fault zone shown by the electromagnetic surveys. These geophysical investigations, coupled with geologic, hydrogeologic (piezometric map), and geomorphologic (3D digital elevation) data have enabled the explanation of the groundwater emergence conditions. Furthermore, the hydrochemical study is con-ducted by collecting and analyzing the groundwater emergences sample in dry season 2020. The physical characteristics and hydrochemical facies using the piper diagram, and Chebotarev evolution sequence were used to determine the origin of the groundwater. The results showed three different types of springs. The Hillslope springs formed on the very rugged slopes of Sindou peaks, whose water comes from rain. The overflow springs or Mound Form, resulting from the emergence, through fractured zones of Kawara Sindou Sandstone, of groundwater at the interface of the sedimentary and crystalline rocks. Finally, the depression springs appear at the outlet of the perimeter and result from the intersection between the ground-water water table and natural ground.