Deriving hybrid reservoir group operation rules for droughts using integrated NSGA-II framework and operation models

Frequent droughts driven by climate change threaten the balance between water supply and demand in river basins. To improve reservoir group operation rules under drought conditions, this study proposes a novel method for deriving hybrid operation rules by integrating an NSGA-II framework with joint operation models. The approach compares the operation results of the joint optimal operation models (JOOM) and the conventional dispatch diagram model (CDDM) to analyze reservoir interactions. A network of linkages among primary reservoirs involved in joint operation is identified. This network is then incorporated into the integrated NSGA-II framework and joint operation network model (JONM) to determine the optimal joint operation trigger water storage (JOTWS) for each joint operation reservoir. These optimized JOTWS values are subsequently implemented in the JONM. A case study in the Yuanhe River Basin demonstrates the method’s effectiveness. The optimized JOTWS values were successfully derived as 5,055 and 26,801 10⁴m³ for the Shankouyan and Jiangkou reservoirs, respectively. These values enable the upstream Shankouyan Reservoir to release 30–50 % of its utilizable capacity to support downstream water users during dry seasons. The improvement ratio in annual total water supply to users by JONM compared to CDDM, relative to JOOM, ranges from 11.09 to 60.38 %, improving water supply reliability, particularly for users dependent on the Jiangkouyan Reservoir. The proposed method enhances adaptive reservoir management under drought scenarios and offers a practical tool for improving regional water resource resilience.