Navigating Water Sustainability: Evolutionary Game Analysis of Cross-Sectoral Collaborative Governance in China

Globally, governments are stepping up their efforts to address water pollution, with an increasing number of countries adopting diverse policies aimed at water sustainability. Effective collaborative governance across various government departments is essential for achieving water sustainability. However, the diverse interests of different departments often lead to interdepartmental conflicts. This study employs a mixed-method approach that integrates qualitative insights with evolutionary game theory to analyze these conflicts. Drawing on semi-structured interviews with 31 Chinese local officials and a systematic review of 179 policy documents and academic studies, the research constructs an evolutionary game model between the Department of Ecology and Environment (DEE) and the Department of Water Resources (DWR) — the two primary government agencies responsible for water sustainability in China. By mathematically analyzing replication dynamics, evolutionary strategies, and the stability of the game system, the study demonstrates that governance effectiveness is maximized when DEEs actively implement water sustainability projects and DWRs provide robust support. The findings highlight how empirical evidence on departmental motivations, constraints, and strategic behaviors can inform the selection of game parameters and model structure. Further results suggest that adjusting incentives, sharing investment costs, and introducing constraint mechanisms can guide both departments toward an ideal equilibrium for collaborative governance. This study expands the theoretical and methodological framework of water governance and offers actionable insights for institutional reform and policy design in water sustainability.