Integrating Ecological Importance and Risk for Restoration Zoning and Ecological Water Demand in the Shiyang River Basin

Effective ecological protection and restoration in arid inland river basins requires a holistic perspective of territorial spatial planning that balances conservation and rehabilitation in a dynamic and integrated manner. This necessitates a dual focus: safeguarding key ecological functional zones to maintain the continuity of ecological processes and the spatial connectivity of natural elements, while also implementing targeted, typology-based interventions to enhance self-organizing capacities of degraded ecosystems. Such strategies aim to stabilize ecological foundations and ensure the sustained delivery of ecosystem functions. Taking the Shiyang River Basin as a representative case, this study establishes a technical framework to delineate mountain, oasis, and desert ecosystems across the basin. Using multi-source data and quantitative approaches, we analyze the spatiotemporal evolution of ecological importance and ecological risk from 1990 to 2020. Based on these assessments, we delineate ecological protection and restoration zones and calculate ecological water demand to support precise and efficient management interventions. The results reveal that: (1) The spatial distribution of mountain, oasis, and desert systems in the Shiyang River Basin exhibits pronounced regional differentiation from southwest to northeast, with mountainous and desert systems dominating, while oasis areas remain relatively limited. (2) From 1990 to 2020, the index of ecosystem service importance increased significantly, rising from an average of 12.658 to 15.495. This growth followed a southwest-to-northeast gradient, indicating a spatial pattern of "high in the southwest, low in the northeast." (3) Over the same period, ecological risk across the basin showed an overall upward trend, with the average risk index increasing from 3.844 to 3.904. The spatial pattern of risk grades followed an ascending order across mountain, oasis, and desert systems, with the oasis system experiencing the most pronounced rise in ecological risk. (4) In 2020, the total ecological water demand of the Shiyang River Basin reached 34.043 billion m³, with a spatial distribution pattern of “high in the south, low in the north”. The ecological core zones, restoration areas, and wilderness protection zones had the highest total ecological water demands, while the ecological reserve and buffer zones showed higher water demand per unit area. (5) Delineating ecological protection and restoration zones at the grid scale based on ecological importance and risk, alongside corresponding ecological water demand accounting, provides a robust foundation for refined and effective ecological governance in inland river basins. This approach holds significant implications for advancing ecological civilization and promoting sustainable development in arid regions.