Based on the river system and engineering topological structure and composition characteristics of the SouthtoNorth Water Diversion Project in Jiangsu Province, a joint optimization scheduling model for riverlakestation system in complex plain river network regions was established. A hybrid model solution algorithm, named DPSAPOA(dynamic programming successive approximationprogressive optimality algorithm), was proposed. By simulating the system scheduling process under multiple scenarios, including typical high, normal, and low flow hydrological years, as well as combinations of multiple operating conditions before and after the completion of the second phase of the SouthtoNorth Water Diversion Eastern Route Project, the effect of the second phase of the Eastern Route Project on the water supply pattern in northern Jiangsu Province was evaluated in terms of total water supply, spatial and temporal distributions of water supply, and water supply peaks. The results show that after the completion of the second phase of the Eastern Route Project, the available water supply in northern Jiangsu Province can increase by approximately 1.65 billion, 1.38 billion, and 1.05 billion m3 in typical high, normal, and low flow years, respectively, representing an increase of approximately 12.6%, 12.5%, and 12.0% compared to the current situation. The water supply to Lianyungang area and sections along the Grand Canal and the Xuhong River has potential for increased supply. Adverse impacts on water supply in northern Jiangsu Province occur only during the peak water use period (June) in low flow years when the volume of water diversion out of the province exceeds 8 billion m3. No negative effects are observed in normal or high flow years.