A new idea for predicting and managing seawater intrusion in coastal channels of the Pearl River, China

The prediction of inland river seawater intrusion limit and the estimation of the river discharge required for mitigating seawater intrusion are crucial for water resources management but proven to be difficult using current approaches. The objective of this study is to propose a new idea for predicting coastal channel seawater intrusion and for estimating river discharges required for the downstream pushing of the intrusion limits in the Modaomen channel of the Pearl River Estuary of China. Toward this end, benthic elevation and the SRTM 30 m DEM data were combined to estimate the cumulative volume of the channel (CVC) under different tidal levels. Then, a series of mathematical equations were developed to estimate the CVC portions occupied by freshwater and seawater, respectively, based on river discharges and water salinity samples from a downstream water pumping station. A case study based on historical records was performed to demonstrate the applicability and robustness of the proposed CVC-based approach. Results indicated that the CVC-based estimates of upstream limits of the seawater intrusion agreed well with the observed data (differences < 20%). Moreover, the proposed methods were able to efficiently and accurately estimate the river discharge required to push an intrusion limit downstream to a given distance. Overall, the novelty of this study is to link the channel volume with the prediction and mitigation of coastal channel inland seawater intrusion.