Evaluation of water ecological security and diagnosis of Obstacles in the Yangtze river delta, China.

The Yangtze River Delta (YRD), as China's socioeconomic core, faces compound pressures from water scarcity, pollution, and ecosystem degradation, with water ecological security emerging as a critical bottleneck for sustainable development. This study aims to construct a comprehensive evaluation system and identify key constraints to provide scientific guidance for urban agglomeration water security management. We innovatively established a four-dimensional evaluation framework encompassing water resource security, water environment security, water ecosystem health, and economic benefit management, employing the TOPSIS model with entropy-CRITIC combined weighting to assess water ecological security across four YRD provinces from 2010 to 2023. Results reveal a three-phase evolutionary pattern with provincial gradient distribution, exposing a "high economic-low ecological" resource curse effect in megacities; water resource security subsystem holds the highest weight (35.23%), indicating the synergistic role of economic regulation and natural restoration in system resilience; and dominant obstacles have shifted from industrial pollution to compound pressures including ecological water deficit, agricultural non-point pollution, and lagging water-saving technologies. This study proposes differentiated zoning strategies and cross-regional collaboration mechanisms, providing theoretical and methodological references for water security management in high-density urban agglomerations with global implications for analogous regions.