An observation study of the combined river discharge and sea level impact on the duration of saltwater intrusion in Pearl River estuary–Modaomen waterway

The saltwater intrusion occurs in many coastal areas worldwide and has become a serious menace to freshwater quality. In the Pearl River estuary, saltwater intrusion has threatened the water supply for residential, agricultural, and industrial uses in the past decades, resulting in ecological and economic losses. In this study, the observed saltwater intrusion records of 10 years (2012 ~ 2021) at 9 stations in the Modaomen waterway, the largest inlet of the Pearl River estuary, were compiled. The time duration of saltwater intrusion was analyzed rather than the traditional distance length, along with the reported annual sea level records and river discharge volumes. The annual duration of saltwater intrusion exhibits spatial variations and is inversely related to the distance from the the Pearl River estuary mouth. In the study area which is near the main estuary mouth of the Pearl River, results from a multiple linear regression show that the observed annual saltwater intrusion days near the main Pearl River estuary mouth could be quantitatively explained by the combination of river discharge (dominant) and relative sea level. This work presents an example to investigate the combined river discharge and sea level impact on saltwater intrusion with annually compiled observed data and from a time-change perspective.