Evaluation Of Climate Change Impact On Stream Flow: A Case Of Wabe Watershed, Omo Gibe River Basin, Ethiopia

Abstract

Climate variability in the frequency and intensity of extreme events on hydrological changes can be affecting almost every aspect of Environmental and human well-being. The main objective of this study was to evaluate the impacts of climate change on Wabe watershed in Omo-Gibe River Basin of Ethiopia. The climate variables (precipitation and temperature) obtained from Coordinated Regional Downscaling Experiment (CORDEX) RCMs simulations under representative concentration pathway (RCP4.5) and (RCP8.5) scenarios. RCMs models RCA4, RACMO22T, CCLM4-8 and their mean Ensemble considered to analysis the impact of climate change at wabe watershed. Bias correction applied to climate variables before transferred to hydrological model (SWAT) to simulate the stream flow of watershed. The annual mean Ensemble model of future projection climate variable showed increased in minimum and maximum temperature by 0.920 C to 1.680 C in minimum temperature, and 0.80 C to 1.180 C in maximum temperature under RCP4.5 and 1.480 C to 2.330 C in minimum and 1.130 C to 2.140 C under RCP8.5 in near and midterm period respectively. The projected, climate drier season highly decreased in precipitation especially spring season with maximum decreased value of -1.92% to - 3.93% in near term and -7.1% to -10.09% in midterm under RCP4.5 and RCP8.5 respectively. The mean annual value of precipitation trend shows that+1.1% to -1.92% in near term period and -1.04% to -3.9% in midterm period under RCP4.5 and RCP8.5 respectively. The model performance evaluation; result shows R2 , NSE and PBIAS using SWAT -CUP with a method of SUFI2 were 0.92, 0.73 and -15.8 % and 0.76, 0.64 and - 23.4% during calibration and validation period respectively. Stream flow was simulated for two consecutive periods (2024–2053) and (2054–2083) for both scenarios and compared with the base period (1990–2019). The result show that at wolkite station the projected mean annual steam flow generally decreased up to -9.16% near term period and -9.22% to -20.2% in midterm periods. The study would be beneficial for, decision makers and all concerned stakeholders in developing adaptation and mitigation strategies to the impact of climate change in the wabe watershed.