Analysis and Characterization of Hydrological Drought Under Future Climate Change Using the SWAT Model in Tana Sub-basin, Ethiopia

Climate variability leads to hydrological extremes (floods and droughts) in Ethiopia, regardless of their intensity, duration, and frequency of occurrence. Therefore, this study focuses on the analysis and characterization of hydrological droughts under the future impacts of climate change using the SWAT model in the Lake Tana sub-basin. Future projections of climate data were obtained from dynamically reduced daily precipitation and temperatures from the CORDEX-Africa Program. The potential impact of climate change was examined under the RCP 4.5 emission scenarios for the time horizon 2011–2031, 2032–2052, and 2053–2073 with the baseline 1986–2005. For this study, the widely used modified Mann–Kendall test was run at a 10% significance level on time series data for each of the seven stations. The result of the Mann–Kendall (S) statistical test indicates that the temperature increases by 0.85 °C per decade and the precipitation increases insignificantly in all seasons. The standard streamflow index (SSFI) was used to characterize hydrological drought under historical and future climate change in the Tana sub-basin. The severity, duration, and frequency of hydrological drought were calculated on time scales from 6 to 24 months. Hydrological drought occurred in the Tana sub-basin due to climate change. This was achieved through the development of drought indices that are capable of timely characterizing and evaluating drought at different temporal scales. Assessing the future impacts of climate change on the characteristics of hydrological droughts is one of the important measures to implement sustainable water resource management and effective disaster mitigation in the sub-basin.