Highlights What are the main findings? A suitable ecological interval of 500-740 km2 for Ebinur Lake was quantitatively delineated by integrating lake basin morphometry, ecological security indices, and resource efficiency. Ecosystem service water use efficiency (ESWUE) exhibits a distinct seasonal peak in April (approx. 10 CNY/m3), significantly surpassing the summer trough. What are the implications of the main findings? Implementing a "Spring Surplus and Autumn Deficit" dynamic regulation strategy allows for precise saline dust control during high-risk windy seasons while minimizing evaporation losses. Current water usage patterns result in a 40% failure rate against the minimum ecological baseline, necessitating the integration of local dynamic regulation with long-term cross-basin water transfer schemes.Highlights What are the main findings? A suitable ecological interval of 500-740 km2 for Ebinur Lake was quantitatively delineated by integrating lake basin morphometry, ecological security indices, and resource efficiency. Ecosystem service water use efficiency (ESWUE) exhibits a distinct seasonal peak in April (approx. 10 CNY/m3), significantly surpassing the summer trough. What are the implications of the main findings? Implementing a "Spring Surplus and Autumn Deficit" dynamic regulation strategy allows for precise saline dust control during high-risk windy seasons while minimizing evaporation losses. Current water usage patterns result in a 40% failure rate against the minimum ecological baseline, necessitating the integration of local dynamic regulation with long-term cross-basin water transfer schemes.Abstract Terminal lakes in arid regions face severe degradation due to the dual pressures of climate change and anthropogenic water consumption. Traditional single-threshold methods for defining ecological water requirements often fail to balance ecosystem stability with water scarcity. To address this, this study constructs a comprehensive framework coupling "Morphometric Stability-Ecological Security Reliability-Resource Use Efficiency" to delineate the suitable ecological interval for Ebinur Lake, the largest saltwater lake in Xinjiang. Using multi-source remote sensing data (Landsat, Sentinel, ICESat, CryoSat), we reconstruct the long-term hydrological dynamics from 2001 to 2023. Results indicate a significant shrinking trend in the lake area, driven primarily by reduced inflow. We jointly consider the lake morphometric breakpoint, the ecological security baseline, and the lower bound of ecosystem service water use efficiency (ESWUE) to determine a minimum suitable ecological area of 500 km2; the regulation upper limit is set at 740 km2 based on the marginal peak of ESWUE. However, monitoring data reveal that the lake falls below the minimum 500 km2 baseline in approximately 40% of months, highlighting a severe ecological deficit risk. Furthermore, ESWUE analysis shows a peak in April (10 CNY/m3), suggesting that, under current climate conditions, a "Spring Surplus and Autumn Deficit" regulation strategy-advancing the replenishment window to the spring windy season-can maximize dust suppression benefits at a lower evaporative cost. This study provides a theoretical basis and methodological paradigm that will contribute to the sustainable management of shrinking terminal lakes globally.