The poor hydrodynamic conditions in the plain river network have resulted in prominent water quality issues. To improve the water environment in the plain river network area, we selected hydrological and water quality monitoring data of flood and dryseasons of 2018 from 19 cross-sections in the Binhu River network in Wuxi, Jiangsu Province. We employed the MIKE21 Binhu River network hydrodynamic-water quality model and a Python-based energy mathematical model to investigate energy dissipation patterns, the relationship between energy and water quality, and the optimal water diversion flow range. The results showed a significant negative correlation between water quality concentration and river energy. Increasing the water diversion within certain limits led to a rise in total river energy; however, upon reaching a threshold, further increases in water diversion caused a gradual decrease in total river energy. By optimizing the water diversion schemes at the energy target level, we effectively harmonized the diverse factors in the water diversion process. This optimization allowed us to determine the daily optimal water diversion flow range and the optimal total energy range for the river network. These findings provide a basis for optimizing water quantity control to ensure the hydrodynamic and water environmental conditions of the plain river network.