Climate Change Projections in the Upper Awash River Basin of Ethiopia Using Statistical Downscaling Model

Climate change is becoming a major threat to the economic development of developing countries such as Ethiopia. Therefore, understanding the long-term variation and change of climate variables is crucial in developing a plan for sustainable development. This study aimed to project and analyze future climate change in the Upper Awash Basin (UARB) using a statistical downscaling model. Daily data was used every 30-year interval from the second generation of the Earth System Model (CanESM2) under three Representative Concentration Pathways (RCPs). The observed maximum and minimum temperature and precipitation values are a good simulation of the modeled data during the calibration and validation periods using the Pearson coefficient(R), the correlation coefficient(R2), and the Nash-Sutcliffe efficiency (NSE). The downscaled results showed that the mean maximum temperature of upper Awash river basin is likely to increase in the range of 0.32– 0.77°C for RCP4.5 in the 2050s (2041–2070) and 0.43-1.16°C in 2080s (2071–2099), whereas under the worst emission scenario (RCP8.5), the mean maximum temperature of the study area will increase in between 0.52-0.96°C in 2050s and 1.27-2.19°C in 2080s respectively. In the high emission scenario RCP 8.5, the monthly mean maximum temperature increases by 0.5 to 20c in the mid and end of the century. Under medium and high emission scenarios of the far-future period (2080s), the mean annual precipitation will increase by 10.2% and 21.5% compared to the reference period. In both RCP 4.5 and RCP 8.5, rainfall in the Bega/dry season is expected to increase in the 2050s and 2080s while Belg's (February–May) in all emission scenarios for all periods. Whereas in the RCP 4.5 and 8.5 emission scenarios, the Kiremit season is expected to increase in the 2050s and 2080s by 4.6 and 13.9%, respectively. In general, the increase in temperature could worsen the environmental conditions in warm seasons; and an increase in precipitation in the Kiremt season is expected to bring a likely risk of flooding