Supply Chain Assessment of Water Scarcity and Management Measures in Chinese Cities Based on Water Quantity and Quality

China is facing the dual pressure of water scarcity, in terms of both quantity and quality. Existing studies often ignore the monthly variation in water quality and lack an integrated prefectural-level assessment of quantity–quality–environmental flow requirement (EFR) water scarcity. Moreover, conventional methods for estimating water scarcity risk depend on subjective assumptions and ignore adaptive behaviors, limiting accuracy. This study developed a multiagent complex network model integrating monthly data on water quality from 3,646 national monitoring stations, municipal water use inventories, and EFR constraints to assess water scarcity-induced supply chain losses. Findings show that incorporating water quality restrictions increases water-scarce cities from 81 to 89, the shortage volume by 17.7%, and losses by 5%. Several cities, such as Lanzhou, Shanghai, Zhengzhou, and Taiyuan, have experienced a localized water scarcity with significant impacts. Water quality-related losses are concentrated in the industrialized northern plains. We evaluated three management strategies: water quality improvement, reclaimed water use, and the Water Diversion Project. Their combined implementation reduced water scarcity in 62 cities and generated benefits of 39–40.7 billion Chinese Yuan. This study quantifies the impacts of water scarcity on cross-regional and cross-sectoral supply chains and provides essential evidence for guiding sustainable and resilient water management.