EVALUATION OF THE IMPACTS OF CLIMATE CHANGE ON SEDIMENT YIELD FROM THE KATAR WATERSHED, CENTRAL RIFT-VALLEY BASIN, ETHIOPIA

Abstract

Climate change is one of the issues that, the world facing today including Ethiopia and it is anticipated that climate change will impact sediment yield in watersheds. The purpose of this study was to investigate the impacts of climate change on sediment yield from the Katar watershed in the Eastern Lake Ziway Basin, Ethiopia. Here, used the coordinated regional climate downscaling experiment (CORDEX)-Africa data outputs of Hadley Global Environment Model 2-Earth System (HadGEM2-ES) under representative concentration pathway (RCP) scenarios (RCP4.5). The analysis was performed in two future projection of 2030’s and 2060’s under the reference of baseline period of 1987-2017 with their RCP correction. After assessment of missing, quality and consistency of data; bias, the coefficient of variation and correlation were used to evaluate the systematic error of precipitation amount, the degree of precipitation variability and bias-corrected before serving as input to the impact analysis A Soil and Water Assessment Tool (SWAT) model was constructed to simulate the hydrological and the sedimentological responses to climate change. The model performance was calibrated and validated using the coefficient of determination (R2 ) and Nash–Sutcliffe efficiency (NSE). The results of the calibration and the validation of the sediment yield R2 and NSE were 0.65 and 0.61, and 0.66 and 0.65, respectively. Climate change output from this research shows that the watershed will get warmer in the future. Both minimum and maximum temperature of the catchment have an increasing trend by 1.04 0C for 2030’s and 2.04 0C for 2060’s for minimum temperature and 0.90 0C for 2030’s and 1.56 0C for 2060’s for maximum temperature. Also, average annual rainfall shows increase by 4.8% for 2030’s and 1.6 % for 2060’s. The results of downscaled precipitation and temperature increased in both future period under RCP4.5 scenario. These climate variable increments were expected to result in intensifications in the mean annual sediment yield of 41.1% and 8.9% for RCP4.5 by the 2030s and the 2060s, respectively. The average annual sediment yield were 398 ton/km2 and 307 ton/km2 for the 2030’s and 2060’s, respectively. From this study, the results show that the sediment yield of the watershed is likely to increase under climate change scenarios. This will help water resources managers make informed decisions regarding the planning, management, and mitigation of the river basins.