Projecting the impact of climate change on precipitation amount distribution and scenarioin the Awash River Basin (Ethiopia) through gcm downscaling

The objective of this research is to develop climate change scenario for precipitation case over Awash River Basin in Ethiopia under three representative concentration pathways (RCPs) of greenhouse gases in atmosphere which stabilising radiative forcing scenarios at 2.6, 4.5 and 8.5 Wm-2 until year 2100, indicated as RCP2.6, RCP4.5 and RCP8.5, respectively. The method used to generate climate change scenarios for each RCPs is Statistical Downscaling Method (SDSM) of climate scenarios from global to regional scale. For performance of SDSM model calibration and evaluation Nash-Sutcliffe efficiency (NSE) and determination coefficients (R2) are used. The results in this study showed that the SDSM model demonstrated moderate to very good strength (R2 ≥ 0.7; NSE ≥ 0.7) for calibration and validation coefficient values on average, respectively. Concerning climate change scenario projections, future changes are expected to be slight or moderate until the 2020s. However, after this period, the model predict an increase in annual precipitation amount, especially in the medium and high emission scenarios (RCP4.5 and RCP8.5). Significant change is observed in the periods 2050s and 2080s under each RCP. Regarding monthly precipitation performance the model exhibited an increase rainfall ranging from +1% up to +85%, but on some months a decrease is observed ranging from -1% up to -40%, compared to the baseline period (1983–2016). On seasonal basis, in Upper and Middle Awash River Basin the highest change in precipitation amount increment is expected to be in the Belg season (spring). When we consider the future annual precipitation amount, the Lower Awash River Basin is expected to experience the highest increase changes in precipitation amount among all three sub-basins. In general, we conclude that the future precipitation amount will significantly increase in time over the Awash River Basin. As a result, the Awash River Basin will be vulnerable to flooding due to the anticipated increase in precipitation brought on by global climate change; and are likely to have moderate to significant negative impacts on various socioeconomic activities over the communities and natural resources existing over Awash River Basin. Therefore, we recommend that in order to create better climate change adaptation and mitigation mechanisms, decision-makers are provided with this information and consider with other related findings to strengthen the national adaptation and mitigation strategies.