Facing the escalation of extreme climate events, estuarine delta cities like Shanghai grapple with significant water supply challenges. This study employs system dynamics and dynamic adaptive policy pathways to assess Shanghai's water supply security risks and responsive strategies in 2022-2050, amidst extreme climate conditions. Utilizing data from 2000 to 2021, we constructed a system dynamics model to predict future water demand under various development modes. Focusing on the unusual 2022 drought in the Yangtze River Basin, we simulated 15 scenarios, including economy, population, water efficiency, and reservoir levels, to identify the extent and timing of potential water supply risks, then proposed pertinent dynamic adaptive strategies to address them. Our findings suggest that the 2022 drought significantly reduced Shanghai's water supply capacity, leading to a notable deficit. Under scenarios of accelerated economic growth, water supply security risks are heightened, with projections indicating a reduction of days of supply available to merely 33-67 days, and escalating water shortage amount to 592-896 million m3 by 2050. Short-to-medium-term recommendations include optimizing both local and transit water resources, strengthening emergency water reserves, enhancing water use efficiency, and maintaining stable reservoir water levels. For the long term, expanding water storage infrastructure and promoting integrated water resource management within the Yangtze River Delta is key to establishing a resilient and diversified water supply system, effectively mitigating future water security risks. This study provides a scientific basis and reference for the sustainable management of water resources in estuarine cities confronting normalized extreme climate conditions. It offers valuable insights for policymakers and actionable suggestions for urban planners.