Simulation and Strategy for Salinity Control Scheduling in Dongjiang Delta of Pearl River Basin in Severe Drought Year

In recent years, the saltwater intrusion in the Pearl River Estuary has intensified, with a significantly expanded impact range. During the dry season from 2021 to 2022, the Dongjiang Delta experienced the most severe saltwater intrusion on record. Based on the river discharge, pondage, and salinity data of the Dongjiang Basin from 2021 to 2022, this paper analyzed the hydrological characteristics and the saltwater intrusion patterns in the Dongjiang Delta. The numerical Finite Volume Coastal Ocean Model (FVCOM) was used to simulate the salinity control dispatching, and the key parameters such as the river discharge and timing of salinity control dispatching in the Dongjiang Delta in the severe drought year were explored. The research finds that the Dongjiang Basin suffered a severe drought year in 2021, with an annual average river discharge at the upstream Boluo Station being 64.5% lower than the multi-year average value. In the Dongjiang Delta, saltwater intrusion peaked during spring tides and dropped during neap tides. Due to the weak capacity of regulation and storage in Dongguan City, the strategy for salinity control dispatching in the Dongjiang Delta is to release fresh water throughout the duration of spring tides. In order to cope with the more adverse situation that the drought may continue, the average daily river discharge at the Boluo Station should be regulated to not less than 280 m³/s during the spring tides and not less than 212 m³/s during other periods. This will essentially ensure the water supply security in the Dongjiang Delta. This paper provides some reference for the river discharge dispatching and salinity control during the dry season in the Dongjiang Delta.