Mapping Water Yield Service Flows in the Transnational Area of Tumen River

Ecosystem service flows are critical linkages between ecological supply and human demand. As a vital component of ecosystem services, water yield service is essential for human survival and development. Therefore, it is of great significance to explore the supply–demand relationship of water yield service and its spatial flow process. This study investigates the supply–demand dynamics and spatial flow of water yield service in the transnational area of Tumen River (2000–2020), utilizing the InVEST model and the miniature delivery-path-mechanism model. The results show the following: (1) From 2000 to 2020, the supply of water yield service in the Tumen River Basin exhibited a spatial distribution pattern of “low center, high surrounding”, with significant spatial heterogeneity in the distribution of supply and demand. (2) Despite the substantial surplus of water yield service in the study area, the ecosystem service supply–demand ratio (ESDR) shows an overall declining trend. The dominant spatial mismatch type is high-supply–low-demand (HL type) zones, primarily located in mountainous and hilly areas, accounting for over 40% of the total identified pixel types. (3) Driven by economic and social development, the spatial scope of water yield service flow has gradually expanded. Supply-side flows initially increased before declining, while demand-side flows followed the opposite trend. By mapping ecosystem service flows, this study provides a reference and basis for establishing the regional ecological compensation mechanism and promoting integrated water resource management, both of which are crucial for the long-term sustainable development of the basin.