Water system sustainability of China’s Yellow River Basin: A Refactoring and integrated evaluation based on the sustainable development Goal 6

• SDG-6 assesses Yellow River Basin’s water system sustainability from 2015 to 2022. • Integrates water resources-environment-ecology-activities into a unified framework. • Offers replicable model for assessing river basin sustainability worldwide. • Gini index reveals improved equity, declining from 0.257 to 0.229. • Innovative metrics reveal dynamic spatiotemporal evolution of system coordination. Effective water system management is essential for achieving sustainable development in large river basins, yet the interactions among water resources, environment, ecology, and human actions remain inadequately explored. Focusing on the Yellow River Basin, a critical ecological and economic corridor, this study investigates the spatiotemporal evolution of coupling coordination and environmental equity within the water resource-environment-ecology-actions system from 2015 to 2022. Using coupling coordination analysis, and the Gini index, the results reveal a gradual improvement in environmental equity, as evidenced by a decrease in the Gini index from 0.257 to 0.229, indicating a more equitable distribution of water resources. Despite this progress, the coupling coordination degree remains at the “borderline disorder” stage, with significant regional variability driven by disparities in socio-economic development and geographical conditions. Upstream areas demonstrate improved coordination due to enhanced ecological restoration and governance, whereas downstream regions experience greater pressures from industrial growth and population expansion. Structural equation modeling highlights the stabilizing role of water resources in improving water system sustainability, while the effects of water ecology and human actions exhibit region-specific variations. This study provides a comprehensive understanding of the dynamic relationships within the water system, emphasizing the need for regionally tailored strategies to address disparities, enhance coordination, and integrate ecological restoration with sustainable water management. These findings and the proposed analytical framework offer valuable guidance for advancing water system sustainability in the Yellow River Basin and other large-scale river systems globally.