Modeling future climate change impacts on hydrology using CORDEX data and QSWAT model in Ethiopia’s Upper Tekeze Basin

Climate change affects how water resources are distributed throughout basins in space and time. To maintain the sustainability and resilience of water supplies, meticulous planning is required. It is essential in basins like the Tekeze River Basin, which provides major social and economic advantages. The basin offers huge potential for agriculture and cascaded hydropower. CORDEX RCMs ensemble data for Representative Concentration Pathways 4.5 and 8.5, and observation data, are used to evaluate the future effects of climate change on the water resources of the River basin using the QSWAT hydrologic model. Results show a decreasing trend at mid-century mean annual rainfall scenario under RCP 4.5 and RCP 8.5 at an average annual rate of -1.32 mm/year and -0.32 mm/year, respectively. The mean annual maximum temperature scenario depicts a decline trend at a rate of -0.0510 C/year and -0.0020 C/year under RCP 4.5 and RCP 8.5, respectively. While, minimum temperature shows, a significant increase at a rate of 0.0610 C/year under RCP 4.5 and 0.0850 C/year under RCP 8.5 scenario. Under the RCP 4.5 scenario, the mid-century analysis of the main water balance components—relative to the base period—shows a decreasing trend in all elements except for potential evapotranspiration, which increases. In contrast, under the RCP 8.5 scenario, most components exhibit increasing trends, with the exceptions of precipitation, surface runoff, and total water yield, which all show a decline. The QSWAT model performance evaluation results for NSE, R2, and PBIA are 0.92, 0.93, and -13.2 for calibration and 0.93, 0.94, and -1.6 for validation, respectively. Furthermore, the uncertainty analysis results for the p-factor and r-factor for calibration and validation are 0.68, 0.87, and 0.71, 0.84, respectively. These results show good agreement between the simulated and observed flow. Moreover, these results could indicate that the QSWAT and CORDEX models have acceptable performance in the northern Ethiopia.The results obtained, and the techniques applied in this research, could have an important contribution to the development of resilient and sustainable water resources management policies and decision-making systems in the basin. Furthermore, the applied techniques could have transferability to other river basins in the country and beyond.