The Aswan High Dam Reservoir management system was developed to simulate dam operation under varying boundary conditions taking as example climate change and Millennium Dam construction, and analyze the optimal operation rules of the reservoir taking into account a large number of objectives, including hydropower production and water supply for irrigation purposes. The developed system runs on Windows platforms and comprises three basic modules: a user-friendly graphical interface managing all graphic features, a computational engine where all the algorithms are implemented, and a database and files module managing hydrological and operational data. The developed model was calibrated. The future hydrologic scenarios developed have been used to assess the expected impacts of potential climate change (baseline and three periods with two global emission scenarios) and the Millennium Dam. The new operation rules were used for scenarios analysis. It was concluded that overall applying the new operation rules will decrease the percentage of occurrence of minimum water levels. Also, the Millennium Dam will increase the percentage of occurrence of minimum water levels. Finally, the period III (2070–2099) for the two global emission scenarios is very critical for the dam operation.