A Dynamic Calculation Method for Water Supply Benefits of Water Diversion Projects Incorporating Ecological Benefits

Ecological water supply has been integrated into the water supply scope of numerous water diversion projects, yet ecosystem complexity makes ecological benefit assessment difficult. Traditional quantitative methods for water supply benefits mainly focus on economic benefits from productive and domestic water use, ignoring the ecological benefits and real-time benefit changes over the project service period. This study categorizes ecological water supply separately in benefit calculation and considers enhanced ecosystem service value brought by ecological water replenishment. Based on emergy analysis, the water resource values of domestic, productive, and ecological water supply are calculated individually, and a water supply benefits evaluation model is established in combination with corresponding water supply volumes. A dynamic evaluation method for the project service period is further proposed using a Grey Model (1,1). Verified via the Yangtze-to-Huaihe Water Diversion Project (Henan section), results indicate that from 2021 to 2070, comprehensive water supply benefits increase yearly from 5.19 billion yuan to 16.18 billion yuan. Productive water supply provides the largest benefits (67–74%), followed by urban domestic (19–25%), rural domestic (5–7%), and ecological water supply (1–2%). This study constructs a comprehensive, systematic, and dynamic evaluation system, supporting the holistic assessment of the long-term economic and environmental impacts of water diversion projects.