Multivariate approach to assess groundwater resources in the multilayer system of Iullemmeden basin in Dosso Region, Southwestern Niger

The Iullemmeden basin groundwater resources were assessed in the Dosso Region for the groundwater management. This study applied multivariate statistical analyses and classical tools of hydrogeochemistry to identify the main factors impacting groundwater mineralization. The results indicate the occurrence of acidic to basic fresh groundwaters but with excessive mineralization in some places. Good to excellent drinking groundwaters are largely represented in the system. The categorization of groundwater patterns evolves from (i) mixed types namely Ca/Mg-HCO₃, Ca/Mg-Cl, Na-Cl/SO₄, Ca-Cl/SO₄ and Ca/Mg-Cl/SO₄ for the Ct³ particularly; to (ii) chloride types such as NaCl, CaCl and MgCl mostly for Ct¹ and Ct²; and (iii) the bicarbonate types precisely Na-HCO₃, Ca-HCO₃, Mg-HCO₃ for Ch. The weathering of silicate minerals and dissolution of carbonate and salts are the major processes in the multilayer system. The increase of EC and salinity in Ct² could come from the relics of ancient seawater during the last regression. To a lesser extent, fertilizers from agriculture, and livestock farming also contribute to groundwater mineralization and nitrate contamination in the study area. The groundwater assessment of the Iullemmeden sedimentary basin in the Dosso Region revealed the main factors and processes characterizing each aquifer of this system, which can be helpful for better groundwater resource management.