Résumé
In a development and climatic change context, it appears necessary to update our knowledge of the hydrology of the Niger River and its tributaries. The presented work focuses on the Bani, principal tributary of the Upper Niger. The results show that the basin rainfall dropped by 15-25% since the beginning of the drought in 1970, but at the outlet of the watershed, in Douna (101 200 km(2)), the annual flows dropped by >65%. The geology of the watershed could explain this important shift. However, these results are related to the reliability of the low-flow data and to the anthropization of the Bani basin, which is probably underestimated as a non-exhaustive inventory of hydro-agricultural installations, which are shown in the basin. This could have an influence which has not yet been evaluated.