Analysis on the change trend and influencing factors of seawater intrusion in Shenzhen from 2017 to 2022

Based on the data of 25 monitoring wells on seawater intrusion in Shenzhen, from 2017 to 2022, and using Cl⁻ concentration as the evaluation index, the spatial distribution and variation trend of seawater intrusion in Shenzhen were analyzed. Results show that the buried groundwater layer in Shenzhen is relatively shallow, and the change of water level elevation was relatively stable. Seawater intrusion was detected mainly in the Shajing area of Bao’an, the central area of Nanshan, the Yantian Free Trade Zone, and the mouth of the Kwai Chung River in Dapeng. Meanwhile, the factors including regional geology, rock and soil types, resistivity geophysical prospecting, rainfall changes, and human activities were considered, and results show that the exploitation of groundwater is an important factor causing seawater intrusion. The Quaternary faults are potential channels for seawater intrusion. The land reclamation area is vulnerable to seawater intrusion. The correlation between rainfall and seawater intrusion is small. This study provided a reference for the disaster prevention of seawater intrusion in Shenzhen.