Practice and reflection on the construction of suppressing saltwater and replenishing freshwater and second line of defense in the Datengxia Water Complex

The Datengxia Water Complex (hereinafter referred to as the "Datengxia Project") is a key control project in the Pearl River Basin integrating functions such as flood control, shipping, hydropower generation, water resource allocation, and irrigation with multiple regulation targets and great difficulty. In response to the adverse situation where salt tide activities at the Pearl River Estuary threaten the water safety of local residents, the Datengxia Project, as the second line of defense in the "three lines of defense" for water supply security in the Pearl River Basin, overcame the influences of extreme climate processes such as the first dry year(2023) of inflow at the Datengxia dam site since 1936 and the sudden turn of floods and drought. From 2020 to 2024, the 16 emergency water regulation operations were carried out successively with a cumulative water supply of 2.57 billion m³ of water to Macao and Zhuhai. At the same time, it also improved the river ecology and navigation conditions, effectively guaranteed the regional power supply in Guangxi Zhuang Autonomous Region, and gave full play to the comprehensive benefits of the backbone reservoirs in the basin. This paper comprehensively summarizes the practical experience of the Datengxia Project's participation in the emergency water dispatch for saltwater suppression and freshwater replenishment in the Pearl River Basin from 2020 to 2024. From the perspective of reservoir regulation, it analyzes the existing regulation contradictions and solutions, providing a reference for drought resistance and water supply regulation of the same type of reservoirs.