Study on the river discharge to suppress the saltwater intrusion in the Dongjiang Delta of the Pearl River Basin

In recent years, saltwater intrusion in the Pearl River Estuary has become increasingly severe, expanding its impact from the Modaomen Channel to the Dongjiang Delta. During the dry season of 2021-2022, the Dongjiang Delta experienced the most severe recorded saltwater intrusion event. Based on the chlorine content of water plants in Dongjiang Delta, upstream river discharge, downstream tidal levels and the chlorine content at the top of the Lingdingyang Bay from 2009 to 2022, this paper identifies the law of saltwater intrusion in Dongjiang Delta and quantitatively analyzes the response relationship of saltwater intrusion to river discharge at Boluo Station. It is found that the peak of saltwater intrusion in Dongjiang delta generally occurs during spring tide, and the intensity of saltwater intrusion weakens during neap tide. The river discharge is the most important impact factor on saltwater intrusion in the Dongjiang Delta. When the river discharge of Boluo Station is greater than 320 m³/s, the water supply in the Dongjiang Delta is generally unaffected by saltwater intrusion. Under the condition of low river discharge, the chlorine content at the top of the Lingdingyang Bay significantly affects saltwater intrusion in the Dongjiang Delta, and the correlation coefficient with the maximum daily chlorinity of the second water plant at the lower reaches of Dongjiang Delta is 0.70. The tidal range of Sishengwei Station plays the second role, and the correlation coefficient with the maximum daily chlorinity of the second water plant is 0.40. For the extremely dry years, to address the potential for prolonged drought situations, it is suggested that the minimum river discharge of Boluo Section that suppressing the saltwater intrusion should be controlled at least 280 m³/s from the perspective of scientific and rational utilization of water resources. This study can provide theoretical support for the regional scheduling and control of the saltwater intrusion.