Özet:

Ethiopia is experiencing an increasing water security risk owing to a climate change, which caused frequent draught and flooding. The increase in temperature and precipitation variability has reduced streamflow amplifying water security problems. However, evaluation of how the long-term streamflow behaves under the future climate change in the catchment are limited. Thus, the purpose of this study was to investigate the impacts of climate change on streamflow of Sululta catchment using Soil and Water Assessment Tool (SWAT) model under the RCP4.5 and RCP8.5 climate scenarios. Precipitation and temperature outputs from Rossby Center Regional Atmospheric model (RCA4) regional climate model (RCM) was bias corrected against observed data using Power transformation and variance scaling, respectively. The SWAT model was calibrated and validated using observed stream flow. The performance of SWAT model in streamflow simulation showed a good agreement with R2 0.75 and 0.7 and NSE 0.71 and 0.7 during calibration and validation respectively. The projection of climate change shows precipitation decreases in dry season whereas temperature increases under both RCP4.5 and RCP8.5 scenarios. The simulation of streamflow shows that, mean annual stream flow will be increased by 11.91% in 2021s (2021-2050) and by 5.26% in 2051s (2051-2080) under RCP4.5. Under RCP8.5 climate scenarios, the mean annual streamflow will be decreased by 0.98% in 2021s and 1.43% in 2051s. The outcomes suggest that it is important to consider the influence of climate change on streamflow to frame appropriate guidelines for planning and management.

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