In this manuscript the primary goal is to assess how climate change affects the availability and variability of water resources, which directly impacts the efficiency and reliability of hydroelectric energy production. The study aims to understand changes in precipitation patterns, snowmelt timings, and extreme weather events, which influence river flow dynamics, reservoir levels, and overall energy generation capacity. It also seeks to identify adaptive strategies to mitigate negative impacts and ensure sustainable hydropower development in the face of a changing climate. This study evaluates the performance of the Karun 4 Dam power plant, one of the country’s most critical electricity generation facilities, under the impacts of climate change. A multi-criteria decision-making approach (TOPSIS) was used to identify the most reliable General Circulation Models (GCMs) and reduce uncertainty. Additionally, the IHACRES conceptual model was employed to simulate the runoff process, while the Differential Evolution (DE) algorithm was applied to optimize hydropower energy production. The findings show a projected temperature increase from 2040 to 2061 of 1.95°C and 2.34°C under the RCP 4.5 and RCP 8.5 scenarios, respectively, compared to the baseline period (1984-2005). Furthermore, the study predicts a reduction in inflow runoff to the Karun 4 reservoir by an average of 19% and 43% under the aforementioned scenarios. Based on the results, the decrease in reservoir inflow in future periods is expected to reduce annual electricity production by 9% under the RCP 4.5 scenario and 18% under the RCP 8.5 scenario relative to the plant’s nominal capacity.