Assessment of climate change impact on hydro-climatic variables and its trends over Gidabo Watershed

This study assesses the possible impacts of climate change (cc) on the patterns of hydro-climate variables at local scales of the Gidabo watershed in Southern Ethiopia. The Coordinated Regional Climate Downscaling Experiment (CORDEX)-Africa data output of Hadley Global Environment Model 2-Earth System (HadGEM2-ES) was selected under the Representative Concentration Pathways (RCP) scenarios. The streamflow projection by the Hydrologic Engineering Centers-Hydrologic Modeling System (HEC-HMS) model. The HEC-HMS model showed good agreement with the calibration and verification period in the studied four age stations. Then, the areal mean annual (ama) climate-variables trends were assessed by Mann-Kendall (MK) Sen's graphics method and Z statistics. Finally, the impact on future monthly, seasonal, and annual hydro-climate variables was quantified to the baseline period. The results revealed that the climate is successfully projected for given weather stations. The MK trend of ama minimum and maximum temperature (T-min and T-max), and potential-evapotranspiration (PET) show significantly increasing whereas rainfall (RF) and streamflow show insignificantly decreasing. And also, the deviation to baseline period of RF - 58.7%, - 34.5% and - 62.2%; temperature + 1.15%, + 2.2% and + 4.2%; PET + 55.5%, + 73% and + 99.9%; and streamflow - 2.63%, - 2.17% and - 3.63% in Meeso, - 0.27%, - 0.20% and - 0.40% in Kolla, + 0.40%, + 0.13% and + 0.53% in Aposto and - 0.13%, - 0.10% and - 0.03% in Bedessa under RCP2.6, RCP4.5 and RCP8.5, respectively. Thus, the decrement in ama and seasonal RF and the increment in temperature lead to more PET and directly affecting the streamflow negatively. Therefore, constantly monitored and updated appropriate interventions in sustainable natural resource management and development are needed in the watershed.