Assessment of Urban Water Environment Resilience and Vulnerability: Hsintien River Watershed in Taiwan

The Hsintien River is a major watershed for water supply in Northern Taiwan, where high population density and urbanization have led to a complex water environment. Therefore, this study aims to develop a water environment resilience assessment framework applicable to Taiwan by integrating "Water Quality–Quantity–Social Nexus" to examine long-term resilience changes. The results show that upstream resilience is mainly influenced by flow conditions, whereas downstream resilience is constrained by high population density and pollution base loads, leading to insufficient dilution effects. Using the extreme drought event of 2020–2021 as a case study, shows that while the upstream reach maintained a stable recovery of resilience, the downstream reach failed to exhibit resilience due to increased ammonia nitrogen (NH₃–N) concentrations resulting from diminished self-purification. In highly urbanized river reaches, observed resilience patterns are not fully explained by flow conditions alone but are also influenced by pollution pressures associated with urbanization.