Variability, Trends, and Breaks in Hydroclimatic Data in the Senegal River Watershed: The Case of Daka Saidou-Manantali-Bakel

The Senegal River basin is subject to significant hydroclimatic variability, and given the growing influence of water management projects, this study focuses on analyzing trends, shifts, and variability in hydroclimatic parameters along the Manantali-Bakel corridor to assess the combined effects of, on the one hand, climate change and, on the other hand, regulation by the Manantali Dam. In this study, the analysis focuses on hydrometric data from Bakel and several sub-basins (Bafing, Faleme, Gourbassi, Oualia, and Dakka-Saidou), as well as precipitation data observed between 1987 and 2024. The methods used include the Mann-Kendall test, Pettitt’s trend-break test, the Bayesian approach by Lee and Heghinian, and the analysis of autocorrelation plots. The results reveal high interannual variability in streamflow and precipitation, marked in particular by significant negative trends in May and June (Kendall’s τ ranging from −0.37 to −0.41; p < 0.05) associated with deficits exceeding 95%, and marked changes in the hydrological regime known to result from the impact of flow regulation, with statistically significant breaks identified by the Bayesian approach (maximum likelihood of 0.32 at Bakel and 0.70 at Dakka-Saidou). The very low signal persistence observed limited to lags 1 through 5 and 9 through 10 in the autocorrelation plot for the Bakel station may indicate that climatic and anthropogenic forcings have had a more significant impact on recent changes in water resources.