Bridging Scales for Sustainable Watershed Management: A Multi-level Water Resources Optimization Framework for Northwest China's Inland River Basins

Effective water resources management in arid inland river basins is paramount for sustaining ecosystem health and socio-economic development. These basins face severe challenges due to climate change and intensive anthropogenic activities. This study addresses this challenge by developing a novel multi-level (regional, irrigation district, and field-scale) and multi-objective optimization model for water resources allocation in a typical inland river basin of Northwest China. Our approach explicitly incorporates the hydrological connectivity from upstream runoff to downstream consumptive use. We first simulate the available water yield from upstream mountain sources, which serves as the key driver of the basin's water cycle. The model then optimizes cropping patterns using ecological sustainability indicators (e.g., ecological water demand, carbon footprint) to enhance the functional linkage between water use and ecosystem health. A significant innovation of our work is the nested optimization framework that propagates decisions from the regional scale down to the field scale, effectively managing the vertical connectivity in watershed management hierarchies. Furthermore, we employ interval fuzzy programming to handle inherent uncertainties in water supply and demand, ensuring the robustness of the configuration schemes. The results demonstrate that our model can effectively balance economic, social, and ecological objectives, providing Pareto-optimal solutions for decision-makers. Finally, a user-friendly Decision Support System (DSS) has been developed to visualize the outcomes and facilitate the practical application of our research. This DSS provides managers with critical insights into the timing, location, and strategies for water allocation, thereby bridging the gap between connectivity science and on-the-ground watershed management. Our study offers a transferable framework for achieving sustainable water resources governance in data-scarce, water-stressed arid regions.