Évolution spatio-temporelle des teneurs isotopiques (δ2H–δ18O) des eaux de la cuvette lacustre du fleuve Niger (Mali)

Abstract The Niger inland delta is a flooded zone of major economic importance. Evaporation is higher than precipitation and the flooded surfaces depend on Niger and Bani Rivers’ inflow. Rainwater data pointed to an isotopic variability due to various climatic conditions and rainfall origins. In the upper basin, values are influenced by groundwater, sub-surface storage and direct runoff in turn affected by high evaporation rates during the low water stage. Because of low hydraulic gradient, the isotopic variations are dominated by evaporation. Nevertheless, the spatial evolution is not as important as expected. A vapour re-equilibration with the river surface can reduce isotope fractionation.