Evaluation of the Impact of Climate Change on Streamflow, A Case of Mojo River, Upper Awash Basin, Ethiopia.

Abstract

The impact of climate change on streamflow is one of the present-day sensitive issues all over the world. The main objective of this study was to evaluate the impact of climate change streamflow in the Mojo River watershed, Upper Awash River basin, Ethiopia. The observed hydro-meteorological data for the baseline period of 1987-2016 was collected from Ethiopian Ministry of Water,Irrigation and Energy (MoWIE) and Ethiopian Meteorological Agency (EMA). Three Regional Climate Models (RCMs),i.e. RACMO22T, RCA4 and CCLM4-8, derived by one MOHC-HadGEM2-ES Global Climate Model (GCM) were downloaded from CORDEX-Africa, under representative concentration pathways (RCPs)4.5 and 8.5. Each climatic parameter was extracted from RCMs using Arc GIS 10.4.1 and the performance of the model was tested by using r, RMSE, PBIAS, and identified RAMCO22T the better performed than the other. Bias corrections was done by power transformation for the precipitation and variance scale for the temperature equation. The trend of precipitation and temperature was significantly increased and decreasing annually. The simulation was carried out by using the Soil and Water Assessment Tool (SWAT) model under historical (1987-2016) and future climatic scenarios that range between (2022-2051) and (2052-2081). Calibration and validation were performed by using sequential uncertainty fitting version-two (SUFI-2) algorithm in SWAT CUP program utilizing recorded streamflow data of (2000-2015). The Performance of the model was evaluated during calibration (R 2 = 0.71, NSE = 0.70, PBAIS = -13.9) and validation (R 2 = 0.71, NSE = 0.64, PBAIS = -4.7). The projected mean annual maximum temperature showed an increasing trend in the future period (2022-2051), and (2052 - 2081) periods under RCP4.5 by 0.14℃ and 0.7℃, and RCP8.5 scenarios by 0.4℃ and 1.3℃ respectively. Whereas, the minimum temperature will be decreasing by (-1.1 and -0.7) for (2022-2051) and increasing by (1.3 and 1.3) for (2052-2081) periods under RCP4.5 and RCP8.5 scenarios respectively. The annual streamflow will increase by 55% and 57.07% under RCP4.5, and by 55.8% and 58% under RCP8.5 with the future periods of (2051), and (2081) respectively