IMPACT OF CLIMATE CHANGE ON WATER AVAILABILITY IN GIDABO WATERSHED, SOUTHERN ETHIOPIA

Abstract

Climate change significantly affects many hydrological systems, which in turn affects the water resource and the flow of rivers. The aim of this research was to investigate the impacts of future climate change on the water availability of the Gidabo watershed, which is one of the Ethiopian rift Valley sub-basins. Dynamic downscaling model was used as a representative concentration pathway (RCP) scenario for the daily precipitation, maximum and minimum temperature in the watershed. The large-scale climate variables for the RCP4.5 and RCP8.5 scenarios obtained from the Hadley Global environment model through CORDEX-Africa data outputs of HadGEM2-ES were selected under representative concentration pathway. The analysis was performed in two future projection of 2018- 2047’s and 2048-2077’s with baseline period of 1988-2017. Results showed that the average annual max/min temperature will increase by 1.23oC/1.26oC and 2.64oC/3.27oC (for 2018-2047) and by 2.57oC/0.23oC and 3.542oC/2.3oC (2048-2077) for RCP 4.5 and RCP 8.5 respectively. Average annual rainfall decreased 69.19mm and 72.3mm at RCP4.5 and RCP8.5 for (2018-2047) respectively and decreased 79.02mm and 85.12mm at RCP4.5 and RCP8.5 for (2048-2077) respectively. The SWAT hydrological model was used to simulate streamflow together with other water balance components after sensitivity analysis, calibration and validation of the model. The results indicated that water yield decrease by 21.8% and 23.9% of the rainfall in the case of RCP 4.5 and RCP 8.5 respectively. On the other hand, the trend test result on gaged data showed the presence of a no statistically significant trend in the precipitation and significant trend in the minimum temperature at most of the stations.