SWAT model application for calculating ecological flow in sub-basins of the Huangshui River Basin

Ecological flow denotes the minimum volume of water required to sustain the integrity and health of watershed ecosystems, ensuring their stability and functioning over time. However, research on estimating ecological flow at the sub-basin level and developing strategies for ecological water replenishment is still limited. The study begins by utilizing measured runoff data from 1952 to 2020. The SWAT model is then employed to reconstruct the natural runoff, adjusting for hydrological anomalies, and to simulate the runoff for each sub-basin. The ecological flow and water shortage conditions for each sub-basin are calculated using the Tenant method under three standards: minimum, suitable, and ideal. Finally, specific water supplementation strategies are proposed for each sub-basin based on these standards. The study reveals that the Huangshui River Basin has experienced significant development and utilization of its water resources. The reconstructed natural runoff, derived from the SWAT model, is 16% higher than the actual runoff. Significant variations in ecological flow are found across the 28 sub-basins, with sub-basins 19, 20, 22, 25, and 26 identified as facing ecological water shortage. To address the water shortages in these sub-basins, a combination of in-basin water storage and inter-basin water transfer is recommended for sub-basins 20, 22, and 25. And sub-basins 19 and 26 can meet their ecological flow needs using only in-basin water storage. The study's findings establish a robust scientific foundation and offer actionable recommendations for the preservation of the ecological integrity of the Huangshui River Basin.