IMPACTS OF CLIMATE CHANGE ON HYDRO-METEOROLOGICAL DROUGHT ON DAWA WATERSHED, GENALE DAWA RIVER BASIN, ETHIOPIA

Abstract

Climate change is statistical variations over an extended period in the features of the climate system, such as variations in global temperatures and precipitation, caused by human and natural sources. Major occurrence that has an impact on the agricultural, social, economic, and environmental spheres was drought. Understanding climate change affects frequency, length, and severity of hydro meteorological droughts is an issues. In this work coordinated regional climate downscaling experiment for Africa, which integrates climate forecasts from Coupled Model Intercomparison Project5 based on an ensemble of GCM-RCM, were used to statistically downscaled the climate change scenarios.The aim of this study was to estimate climate change impacts on Hydro-meteorological drought for early warning response and development of climate adaptation and mitigation options. The impact of climate changes during a period from 2021-2080 has evaluated by reporting under RCP4.5 and 8.5 scenarios. For the extraction and bias correction of the daily maximum and minimum temperature, as well as precipitation of 30- year overlap periods, CMhyd has employed. DrinC tool was used to characterize the meteorological and hydrological drought. The annually minimum temperatures are predicted to increase by 2.94, 3.45, 3.21, and 3.59°c and annually maximum temperatures increased by 2.61, 2.83, 2.71 and 3.36°c for RCP4.5 and RCP8.5 respectively. Regarding the change in rainfall reveals annual average decreases of 8.45- 9.3% and 10.5-10.95% at RCP4.5 and RCP8.5, respectively. Considering the evaluated parameters, minimum and maximum temperatures increased trends but for the rainfall, large fluctuations predicted. Moreover, in the study years for the parameters in all simulated models, RCP 8.5 scenario estimated a higher amount than RCP 4.5 scenario.HBV models successfully calibrated from 1991-2010 and verified from 2011-2020. Overall, the models monthly time scale calibration R2=0.88 and NSE=0.77 and validation R2=0.86 and NSE=0.83 with the HBV Light model performed well under both scenarios of RCP4.5 and 8.5 for two projected periods. The simulation findings from the HBV indicated that the mean yearly discharge drastically declined in comparison to the baseline periods for both scenarios.Generally, HBV indicates a percentage decrease in the total average annual flow volume of 1.6% to 3.5% and 4.6% to 4.9%. The only increment in Belg season ranges between 39.3% and 40% in 2020s and 39.2% to 38.5% in 2050s. Decreases in mean total annual, seasonal and monthly flow volume seen for times when there is a corresponding decline in mean annual, seasonal, and monthly precipitation. To offset this variation community should adopt various soil and water conservation strategies, using drought tolerant crop in the watershed, implement various trees, appropriately design and apply a water harvesting structure and Surface runoff harvesting to the watershed. As a result, feature research should consider wet number and wet days for drought impacts and more multiple GCM-RCM driving models was used to improve more prediction accuracy in the future climate and drought change.