Driving Mechanisms and Spatial Governance Strategies for Urban–Water Synergy Systems

This study examines urban–water synergy as the spatial coordination between urban expansion and water systems. Using land-use data from 2000 to 2020, the central urban areas of Jingzhou and Anqing are analyzed as representative small and medium-sized cities. Urban–water synergy is assessed across three dimensions: land-use synergy, pathway synergy, and directional synergy. These dimensions are quantified using four indicators: Urban–Water Interaction Intensity (UWII), Urban–Water Interaction Displacement (UWID), Spatial Path Alignment Distance (SPAD), and Directional Alignment Angle (DAA). The results show that Jingzhou and Anqing exhibit two distinct urban–water synergy modes: a convergent interaction mode characterized by increasing alignment in land-use interactions, spatial pathways, and directional tendencies, and a divergent synergy mode characterized by persistent separation across these dimensions. Differences between these synergy modes are associated with expansion pressure, physical template, and institutional mechanisms. Spearman rank correlation and principal component analysis suggest that institutional mechanisms constitute an independent analytical dimension and may be relevant for interpreting potential non-linear changes in urban–water interaction patterns. Based on these findings, this study discusses governance implications centered on institutional effectiveness, supported by spatial restoration and expansion regulation, for informing urban–water synergy governance in small and medium-sized cities.