IMPACT OF CLIMATE CHANGE ON LOCAL HYDROLOGY: A CASE STUDY IN AGULA’E WATERSHED, TEKEZE BASIN, NORTH ETHIOPIA

Abstract

Climate change, nowadays, has significant impact on the water resource system of an area. This study was conducted in Agula’e watershed, Tekeze river basin, Ethiopia, using Water and Energy Transfer through Soil, Plants and Atmosphere (WetSpa) hydrological model and General Circulation Model (GCM) aiming at estimating the impact of climate change on water availability of the study area. By making proper calibration, precipitation and temperature outputs of HadCM3 coupled atmosphere-ocean GCM model for A2a (medium to high) and B2a (Medium to low) SRES emission scenarios were downscaled using Statistical Downscaling Model (SDSM). In 2020s, precipitation, maximum temperature, minimum temperature and potential evapotranspiration will increase by 1.03%, 0.55%, 0.09% and 2.08% for A2a emission scenario and 1.84%, 0.42%, 0.1% and 2.14% for B2a emission scenario respectively. In 2050s, it will be expected an increment trend in precipitation, maximum temperature, minimum temperature and potential evapotranspiration by 0.8%, 1.63%, 0.12% and 3.13% for A2a emission scenario and 3.06%, 1.19%, 0.10% and 2.95% for B2a emission scenario. In 2080s, precipitation, maximum temperature, minimum temperature and potential evapotranspiration will increase by 1.05%, 3.17%, 0.15% and 4.63% % for A2a emission scenario and 1.35%, 1.97%, 0.13% and 3.65% for B2a emission scenario. In the future period, the overall trend in aerial mean maximum temperature, precipitation, and potential evapotranspiration show positive increment by 2.5%, 0.96%, and 3.28% under A2a and 2.05%, 2.12% and 2.91% for B2a emission scenario respectively. Minimum temperature will not show significance change for both emission scenarios. The model showed that precipitation and actual evapotranspiration results in average increment trend by 1.03%, 0.78% and 1.03% for A2a scenario and 1.93%, 3.05% 1.34% for B2a scenario in 2020s, 2050s and 2080s time horizons respectively. In the future time horizons, actual evapotranspiration will be increased by 6.96%, 7.01% and 7.42% under A2a scenario and by 8.49%, 9.91% and 8.25% for the B2a scenario. The overall trend of precipitation and actual evapotranspiration value will increase by 0.95% and 7.13% under A2a emission scenario and 2.11% and 8.88% under B2a emission scenario respectively. Surface runoff will generally has decrement trend in all the future periods and will averagely decrease by 71% for A2a and70% for B2a emission scenarios