A 60-year analysis of past hydroclimatic variability and trends in the Mouhoun river catchment in West Africa.

Understanding past hydroclimatic variability and trends is crucial for enhancing water resources management in West Africa. The aim of the study is to investigate the long-term variability and trends of hydroclimatic variables in the Mouhoun River Catchment at Boromo hydrometric station (MRCB) in Burkina Faso over six decades (1961-2020). The sensitivity of streamflow (Q) on the MRCB to precipitation (P) and potential evapotranspiration (PET) is analyzed using the elasticity concept. The study uses also the Pruned Exact Linear Time method for detecting historical changes in the time series of hydroclimatic variables. The trends in hydrological variables are investigated using the multi-temporal trend and the Theil-Sen approach. The results show non-stationarity in the annual time series of hydroclimatic variables over the MRCB. Multiple changepoints are identified with significant differences between consecutive sub-periods highlighted. The multi-temporal trend analysis between 1961 and 2020 revealed significant and contrasting (downward and/or upward) sub-trends in the time series of P and Q, with overall low to moderate changes observed at the outlet of the MRCB. By revealing significant inter-annual trends in P, PET, and Q, particularly during the rainy season, this study provides a robust evidence base to guide targeted adaptation strategies and sustainable water resources planning in the MRCB.