Study on drought resistance function orientation and drought-limited water level of Three Gorges Reservoir

The frequent occurrence of extreme drought events has posed significant challenges to water supply security in recent years.The drought-limited water level, which is a key indicator for reservoirs to start drought response, plays a crucial role in reservoir drought-resistant operation.The water resource scheduling of Three Gorges Reservoir (TGR) has no clear functional positioning for drought resistance and lacks drought-resistant operation strategies when a fairly severe drought or water supply crisis occurs in the middle and lower reaches of the Changjiang River.To address these limitations, this study analyzed the role of the TGR in the drought mitigation system of the Changjiang River Basin, and the drought-limited water level schemes for different inflow conditions of the TGR and different downstream water demand scenarios were also explored.Besides, key issues such as water storage management during the flood season were discussed.The results indicated that: ① the highest priority for the drought-resistant operation of the TGR should be given to ensuring the water levels at urban water intake points and maintaining the basic ecological functions of the river.The Jingjiang and Hankou River sections should be designated as key areas to address water intake difficulties caused by water level decline, while other water dispatch needs should be appropriately taken into account.② Among the three methods employed, the drought-limited water levels established for the TGR through long-term series method provide a valuable reference.To guarantee a discharge of 6 800, 7 000, 7 200 m³/s during extreme dry water scenarios, the water level of the TGR by the end of October should be impounded to 167.20, 170.00, 172.80 m, respectively.The corresponding water level guarantee rates under current scheduling regulations are 90.9%, 87.3%, 83.6%, respectively.③ It is suggested that water storage during the flood season should be integrated with medium- and long-term hydrological and meteorological forecast, storing part of flood season water as a drought reserve, to strengthen the resilience of the Changjiang River Basin in responding to extreme drought events.The findings can provide a scientific foundation and technical support for the drought-resistant operational strategies of the TGR.