Future drought characterization using multiple drought indices and CMIP-6 Climate Models within Mille Watershed, Lower Awash Basin, Ethiopia

The agricultural sector is vulnerable to extreme droughts, particularly in regions with limited water infrastructure. This study aims to analyze the future characteristics of droughts in Mille watershed under climate change. It employs three drought indices: the Reconnaissance Drought Index, Streamflow Drought Index, and Agricultural Standardized Precipitation Index. The analysis uses baseline data (1985–2014) and future data (2041–2100) downscaled from the Coupled Model Inter-comparison Project 6. Three Global Climate Models like MIROC-6, CMCC, and MRI were used under two Shared Socioeconomic Pathways Scenarios (SSP2-4.5 and SSP5-8.5). The Soil and Water Assessment Tool model was employed to simulate future streamflow for two time periods (the 2050s and the 2080s). The study found that the most severe Reconnaissance Drought Index events in the future will occur in Kombolcha, Mille, Batie, and Sirinka, with magnitudes and frequencies in the 2050s of (-1.51, 4.76%), in 2058 (-1.49, 6.16%), in the 2063s (-1.52,5.65%), and in 2066 (-1.5, 4.48%). However, on an annual scale, extreme and severe hydrological drought events are projected for 2088 (-2.0) and 2091 (-1.51) under the SSP2-4.5 scenario. Agricultural droughts are expected to be more frequent in Mille and Batie compared to other stations. Overall, the Reconnaissance Drought Index indicates a significant drought trend in the past, with an anticipated increase in the frequency and severity of future droughts. The study area is expected to experience relatively fewer hydrological drought events. These findings highlight the need for effective monitoring systems and timely identification of drought events, which are crucial for making informed decisions regarding drought mitigation and water management, particularly in the water-dependent agricultural sector.