Integrated water resources management from a water-energy nexusWater-energy nexus perspective in coastal cities is essential for promoting sustainable urban development. However, the complex interactions and uncertaintiesUncertainties in such nexus systems present substantial challenges for decision-makers. To address these challenges, this study proposes a novel semi-infinite trapezoidal fuzzy programming approach integrated with multi-criteria decision analysisMulti-criteria decision analysis (MCDA) to support robust decision-making for water-energy nexusWater-energy nexus management under uncertaintiesUncertainties. The proposed framework is capable of handling infinite constraint sets characterized by both fuzziness and variability, thereby capturing a wide range of potential system responses. A real-world application in a coastal city is conducted to demonstrate the method’s practicality and effectiveness. Within this context, multiple water supply strategies are evaluated considering decision-makers’ preferences, evolving energy consumption patterns, and varying levels of water resource availability. The results indicate that surface and transferred water sources consistently contribute approximately 70% of the total supply. Concurrently, the share of unconventional sources—including recycled and desalinated water—increased from 15.1 to 20.9% across the two planning periods, reflecting a significant shift toward diversified and resilient water sourcing under tightening supply conditions. Moreover, the embodied electricity consumption associated with different supply sources is assessed, revealing potential trade-offs between energy demand and water security. These insights underscore the importance of adopting flexible, risk-informed resource management approaches in response to uncertain and interdependent water-energy systems. The developed method provides a valuable tool for decision-makers seeking to enhance sustainability, resilience, and efficiency in coastal urban water-energy planning.