An integrated model for optimal water resources allocation under "3 Redlines" water policy of the upper Hanjiang river basin

Study region: The upper Hanjiang river basin, which is a crucial water source for the middle route of the South-to-North Water Diversion Project in China. Study focus: This paper attempts to present a new integrated model for optimal water resources allocation in a typical river basin. In this model, the complex adaptive system framework is applied at the macro level, and the system dynamics simulates the inner response of water user agent at the micro level and China's "3 Redlines " water policy is considered in the optimal module. New hydrological insights for the region: An integrated model is proposed for optimal water re-sources allocation of the upper Hanjiang river basin in the planning years 2025 and 2030, and the NSGA-II algorithm is executed to obtain the Pareto optimal solution set for the optimal allocation of water resources. The results show that there is a significant competitive relationship between environmental objective and economic objective. Water resources tend to flow to industrial water user agent driven by the adaptation to economic objective, to agricultural water user agent and municipal water user agent driven by the adaptation to environmental objective, which can be used for decision-making and provide guidance for further development of water resources allocation.