Determination and application of drought-limited water level of the Three Gorges Reservoir

The Three Gorges Reservoir, a key project in the Yangtze River basin, plays a crucial role in drought prevention in the middle and lower reaches. However, the absence of scientific water-level indicators and targeted management rules for drought control in its operational scheduling has partially constrained the comprehensive utilization efficiency of water resources. To address these limitations, this study proposes the functional positioning of the drought-limited water level （DLWL） and a conceptual framework of its phased determination. A detailed methodology for establishing and implementing a phased DLWL is proposed based on three key perspectives, i.e., temporary raising water levels during the flood season and reverse–order reduction during dry periods, and ensuring adequate water storage during replenishment periods. Taking 2022 as a reference year, the DLWL for the flood season is calculated as 156.6 m and daily DLWLs for the storage and dry periods are determined. A comparative analysis with current operational schemes reveals that implementing DLWL controls can effectively elevate reservoir levels through pre-storage at the end of the flood season, while enhancing both discharge flow and power generation during dry periods. The water level of the Three Gorges Reservoir can be effectively increased by 13.01 m, its maximum power generation capacity by 3.5 billion kW·h, and the number of days with water security in downstream industries by up to 34 d. This study serves as a technical reference for DLWL determination and implementation in the Three Gorges Reservoir and offers scientific support for DLWL application in large-scale comprehensive water conservancy projects in China.