Unravelling the Impacts of Climate Variability on Surface Runoff in the Mouhoun River Catchment (West Africa)

Abstract

This study assesses the impacts of climate variability on surface runoff generation in the Mouhoun River Catchment (MRC) in Burkina Faso, in the West African Sahel. The study uses a combination of observed and reanalysis data over the period 1983–2018 to develop a SWAT model (KGE = 0.77/0.89 in calibration/validation) further used to reconstitute the complete time series for surface runoff. Results show that annual rainfall and surface runoff follow a significant upward trend (rainfall: 4.98 mm·year−1, p-value = 0.029; runoff: 0.45 m3·s−1·year−1, p-value = 0.013). Also, rainfall appears to be the dominant driver of surface runoff (Spearman’s ρ = 0.732, p-value < 0.0001), leading surface runoff at all timescales. Surface runoff is further modulated by potential evapotranspiration with quasi-decadal timescales fluctuations, although being less correlated to surface runoff (Spearman’s ρ = −0.148, p-value = 0.386). The study highlights the added value of the coupling of hydrological modeling and reanalysis datasets to analyze the rainfall–runoff relationship in data-scarce and poorly gauged environments and therefore raises pathways to improve knowledge and understanding of the impacts of climate variability in Sahelian hydrosystems.