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Investigation of the elevation of saltwater wedge due to subsurface dams |
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| Authors: | Qinpeng Chang Tianyuan Zheng Youyuan Chen Xilai Zheng Marc Walther |
| Institution: | 1. College of Environmental Science and Engineering, Ocean University of China, Qingdao, China
Key Laboratory of Marine Environment and Ecological Education, Ocean University of China, Qingdao, China;2. College of Engineering, Ocean University of China, Qingdao, China;3. College of Environmental Science and Engineering, Ocean University of China, Qingdao, China;4. Department of Hydrosciences, Institute for Groundwater Management, Professorship for Contaminant Hydrology, Technische Universität Dresden, Faculty of Environmental Sciences, Dresden, Germany Department of Environmental Informatics, Helmholtz-Centre for Environmental Research–UFZ Leipzig, Leipzig, Germany |
| Abstract: | Subsurface dams are rather effective and used for the prevention of saltwater intrusion in coastal regions around the world. We carried out the laboratory experiments to investigate the elevation of saltwater wedge after the construction of subsurface dams. The elevation of saltwater wedge refers to the upward movement of the downstream saltwater wedge because the subsurface dams obstruct the regional groundwater flow and reduce the freshwater discharge. Consequently, the saltwater wedge cannot further extend in the longitudinal direction but rises in the vertical profile resulting in significant downstream aquifer salinization. In order to quantitatively address this issue, field-scale numerical simulations were conducted to explore the influence of various dam heights, distances, and hydraulic gradients on the elevation of saltwater wedge. Our investigation shows that the upward movement of the saltwater wedge and its areal extension in the vertical domain of the downstream aquifer become more severe with a higher dam and performed a great dependence on the freshwater discharge. Furthermore, the increase of the hydraulic gradient and the dam distance from the sea boundary leads to a more pronounced wedge elevation. This phenomenon comes from the variation of the freshwater discharge due to the modification of dam height, location, and hydraulic gradient. Large freshwater discharge can generate greater repulsive force to restrain the elevation of saltwater wedge. These conclusions provide theoretical references for the behaviour of the freshwater–seawater interface after the construction of subsurface dams and help optimize the design strategy to better utilize the coastal groundwater resources. |
| Keywords: | elevation of saltwater wedge field-scale numerical model freshwater discharge groundwater resources hydraulic gradient saltwater contaminated area seawater intrusion subsurface dam |