Integrating water quality and water quantity to diagnose the health of water metabolism systems in multi-core multi-level urban agglomerations

Urban agglomerations (UAs) are compelled to scrutinize the health of their water systems as the frequency of water crises increases. An urban water system’s health is closely related to metabolism processes. To date, water systems in multi-core multi-level UAs have not been analyzed using water quantity and water quality because of methodological constraints. To address this research gap, we developed an integrated water quality–water quantity model for diagnosing water metabolism systems that could process nested multi-region input-output (MRIO) tables. We coupled the MRIO tables and established two networks, an integrated water quantity–quality metabolism network (IWMN) and a water quantity metabolism network (QWMN). We tested the two networks with data from the Guangdong-Hong Kong-Macao UA and assessed four aspects of the networks’ health, namely vigor, organization, resilience, and collaboration, using ecological network analysis. We discovered that IWMN exhibited lower vigor (internal circulation 10.4%) and organization dominated by dependency (total contribution intensity σ = -23) compared to the QWMN. Polity-driven disparities shaped the robustness distribution, while a mutualism tendency coexisted with a complex exploitation relationship (52.4%), particularly in the core large-sized city of Hong Kong, where 58 new competitive pairs emerged. Thus, we recommend prioritizing Guangdong-Hong Kong-Macao trade optimization for high-water-content products to enhance system health.