Climate change affects the availability of water resources by altering the pattern and magnitude of precipitation, temperature, and streamflow. The projection of climate change impact on the streamflow is used to identify the level of changes and desirable intervention measures. In this research, Soil and Water Assessment Tool (SWAT) model and the regional circulation model (RCM) outputs of CORDEX Africa climate model associated with mid and high-level Representative Concentration Pathways (RCP4.5 and RCP8.5) climate scenarios were used to evaluate the change in streamflow in two future projection scenarios (2041-2070 and 2071-2099). The study is directed to the Upper Wabe Bridge watershed found in the Wabe Shebele basin, Ethiopia. The result shows an increase in mean temperature by 3.46 and 5.15°C for RCP4.5; and 4.78 and 5.88°C for RCP8.5 in mid and long-term periods, respectively. The study also confirmed an increasing trend in annual precipitation by +26.3 and +31.85% for RCP4.5 and RCP8.5 climate scenarios, respectively, at the end of 21^st century. In Kiremt (rainy) season precipitation shows an increasing trend by +44.28% and +59.34% for RCP4.5 and RCP8.5 climate scenarios, respectively, but Bega (dry) season show decreasing trend. The future projected annual streamflow shows increase trends under both climate scenarios in both projection periods. The mean seasonally streamflow decreases in the Belg (short rainy) season by -10.91% and increases in the Kiremt (rainy) season by 17.4%. Hence, the increment trend in streamflow during the Kiremt season will have the utmost significance for the requirement of storage and rainwater harvesting structures for irrigation development during dry season. Therefore, incorporating the possible effect of climate change is vital during water resources planning and development.

Abrupt wet-to-dry (W2D) events represent a damaging natural disaster, exerting more far-reaching impacts on the environment and society than single extreme events. While sub-seasonal and interannual precipitation whiplash have recently been analyzed, hydrological W2D transitions, especially at smaller time scales such as sub-monthly, have yet to be examined. In this study, we quantify changes in the characteristics of hydrological W2D transitions based on soil moisture in Africa and identify the drivers behind these changes. The results show that the total W2D transition has accelerated markedly: transition speed increased by 19 % and duration shortened by 10 % from 1981 to 2024. The area averaged proportion of rapid W2D events to total W2D events has increased from 52 % during 1981–2000 to 58 % during 2001–2024. The spatial extent of rapid W2D transitions has increased significantly. On average, 13 % of the continent has experienced rapid W2D transition in the 1980s, increasing to 17 % after 2010. These findings suggest a general shift from slow to rapid hydrological W2D transitions on a sub-monthly timescale. We further find that the speeding up of W2D transition onset is driven by greater precipitation deficits, higher temperature, and higher evaporative demand during the transition onset period. Overall, the shift from slow to rapid W2D transitions reduces the predictability of hydrological volatility regimes, which has adverse impacts on agriculture, ecological stability, and water resources management.

Abrupt wet-to-dry (W2D) events represent a damaging natural disaster, exerting more far-reaching impacts on the environment and society than single extreme events. While sub-seasonal and interannual precipitation whiplash have recently been analyzed, hydrological W2D transitions, especially at smaller time scales such as sub-monthly, have yet to be examined. In this study, we quantify changes in the characteristics of hydrological W2D transitions based on soil moisture in Africa and identify the drivers behind these changes. The results show that the total W2D transition has accelerated markedly: transition speed increased by 19 % and duration shortened by 10 % from 1981 to 2024. The area averaged proportion of rapid W2D events to total W2D events has increased from 52 % during 1981–2000 to 58 % during 2001–2024. The spatial extent of rapid W2D transitions has increased significantly. On average, 13 % of the continent has experienced rapid W2D transition in the 1980s, increasing to 17 % after 2010. These findings suggest a general shift from slow to rapid hydrological W2D transitions on a sub-monthly timescale. We further find that the speeding up of W2D transition onset is driven by greater precipitation deficits, higher temperature, and higher evaporative demand during the transition onset period. Overall, the shift from slow to rapid W2D transitions reduces the predictability of hydrological volatility regimes, which has adverse impacts on agriculture, ecological stability, and water resources management.