<p>In recent years, the constraints imposed by water pollution on ecosystems and human health have become increasingly salient, making the improvement of governance effectiveness a core agenda for the green transition. Using Jiangsu Province, China as the study setting and questionnaire data (valid sample <i>N</i> = 500), we employ structural equation modeling together with Bootstrap-based mediation testing and multi-group comparisons to build and validate a multidimensional explanatory framework for the effectiveness of water-pollution governance, and to identify and analyze its key determinants, causal pathways, and contextual boundaries. Results indicate that institutional development exerts the strongest net effect on governance outcomes, followed by collaborative mechanisms and the regulatory regime; public environmental awareness exerts a consistently positive influence, whereas the direct effect of resource investment is comparatively small. At the mechanism level, collaborative mechanisms serve as a significant conduit through which institutional development, resource investment, and public awareness affect governance outcomes, and the regulatory regime is likewise pivotal in channeling the effects of institutional development and resource investment; At the contextual level, the output elasticity of resource investment varies markedly with regional conditions, whereas the effects of institutions and public awareness remain relatively stable within the province. The study’s main contribution is to provide empirical evidence on factor coupling and pathway decomposition, showing that water-pollution governance performance is not driven by a single element but is converted into stable outputs through a capability structure of coordination and regulation, and on this basis to propose a reusable diagnostic approach and priority-setting criteria, offering empirical guidance for improving governance performance and advancing the deployment of advanced technologies across diverse contexts.</p>