Quantifying ecohydrological boundaries of groundwater-dependent vegetation restoration in a hyper-arid endorheic basin of northwestern China

Ecosystem management in hyper-arid endorheic basins often faces challenges in achieving sustainable development goals, as restoration efforts tend to prioritize spatial expansion over ecohydrological boundaries. A key challenge is that without ecohydrological boundaries to guide spatial decisions, restoration efforts risk over-stressing groundwater resources in some areas while missing recovery opportunities where most needed. This study introduces an innovative method that integrates ecohydrological limits into the restoration of groundwater-dependent vegetation (GDV) in the middle and lower reaches of the hyper-arid Shule River Basin (SRB) in northwestern China. By applying Eagleson's ecohydrological model and the ordered weighted averaging methods, we estimated the vegetation-water relationship in the region. The results reveal that 9.64% of the entire main area has actual vegetation coverage (M_a) exceeding the optimal threshold (M₀), i.e., surpassing the ecohydrological boundary, while less than 1.69% of the total area falls below optimal levels. These results challenge the assumption that GDV restoration opportunities are widespread; instead, most areas are near equilibrium. Groundwater is shallower (3.79 m) in above-optimal areas, yet GDV coverage in these areas is more sensitive to groundwater decline, showing a steeper decrease with falling water table than in below-optimal areas. Priority zones for restoration or conservation vary with decision scenarios, but consistently concentrate in the western and southeastern basin. Our findings suggest that restoration approaches may need to shift from extensive expansion to precision-based, adaptive strategies, with model-informed, scenario-dependent prioritization of targeted interventions in high-priority areas and protective measures in vulnerable low-priority regions for sustainable GDV restoration.