Evolution analysis and environmental management of intruded aquifers of the Dagu River Basin of China

The seawater intrusion in the Dagu River Basin, China, has attracted intensive attention from the government and scholars. Increasing data have become available with the development of data acquisition technology. This situation brings unprecedented opportunities and challenges to the hydrochemical evolution analysis and improvement of seawater intrusion. The hydrochemical evolution process of groundwater is studied on the basis of our collected data in the Dagu River Basin by using mathematical statistics, end-element mixing, Durov, and Gibbs. The negative influencing factors of the groundwater environment are determined. Results show that the groundwater on the north side of the cutoff wall is mainly affected by residual saltwater, sulfuric acid leakage, and NO− 3 pollution. The groundwater on the south side of the cutoff wall is seriously affected by seawater invasion, followed by NO− 3 pollution. Meanwhile, the groundwater on the west bank of the Dagu River Basin is mainly affected by NO− 3 pollution. The groundwater on the north side of the cutoff wall must be discharged on a large scale for its improvement. Meanwhile, unpolluted water is recharged to renew the groundwater resources. Groundwater exploitation should be reduced, and the exploitation area should be dispersed to mitigate seawater intrusion and increase the recharge of the groundwater resources. NO− 3 pollution mainly comes from the sowing of chemical fertilizers and pesticides and domestic waste. Therefore, we should reduce the use of pesticides and fertilizers to control the generation, storage, and treatment of domestic pollutants strictly. [Display omitted] •The area is divided into three subregions based on Dagu River and the cutoff wall.•Subregion indicates different stages of hydrochemical evolution of groundwater.•The hydrochemical and isotopic compositions are involved in this study.•Seawater intrusion contributed the most to groundwater environmental risks.•Different policy recommendations were given for different environmental risks.