Abstract
Despite the drought observed since 1968 in most of the West African Sahel, runoff and rivers discharges have been increasing in the same region. This trend is related with land use change rather than climate change. This paper aims to describe the regional extension of such a phenomenon and to demonstrate that the increase in runoff is observed from the point scale up to the regional scale. It highlights the opposition of functioning between a Sahelian zone, where the Sahel’s paradox applies, and the Sudanian and Guinean areas, where runoff has been logically decreasing with the rainfall. The current trend is evidenced using experimental runoff plots and discharge data from the local to the regional scales.
Highlights
West Africa has been going through a long-term drought since the end of the 1960s
Rainfall; and discharge data collected on the operational network of Niger, provided by Niger Basin Authority (NBA) (Niger River); comparisons with other basins are allowed by using data provided by G-Eau laboratory (IRD, Montpellier, France)
We showed in this study that the increase in runoff has been observed from the local to the regional scales, whatever the land use change is, in the Sahelian region
Summary
West Africa has been going through a long-term drought since the end of the 1960s. This trend has been noted in the Sahel, but appears to have been attenuated in the last decade in the eastern and central parts of the Sahel. The increase in discharge of the Sahelian Rivers, despite the reduction in rainfall, was first noticed by Albergel [5] in Burkina Faso, the term ―Sahelian Paradox‖ used in the following to designate this unexpected behavior. Similar observations were made for the Nakambé River, one of the main tributaries of the Upper Volta River in Burkina Faso [7], and for the right bank tributaries of the Niger
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