气候变化领域集成服务门户(CCPortal): Combining resistivity and frequency domain electromagnetic methods to investigate submarine groundwater discharge in the littoral zone

CCPortal

DOI	10.5194/hess-24-3539-2020
	Combining resistivity and frequency domain electromagnetic methods to investigate submarine groundwater discharge in the littoral zone
	Paepen M.; Hanssens D.; De Smedt P.; Walraevens K.; Hermans T.
发表日期	2020
ISSN	1027-5606
起始页码	3539
结束页码	3555
卷号	24 期号:7
英文摘要	Submarine groundwater discharge (SGD) is an important gateway for nutrients and pollutants from land to sea. While understanding SGD is crucial for managing nearshore ecosystems and coastal freshwater reserves, studying this discharge is complicated by its occurrence at the limit between land and sea, a dynamic environment. This practical difficulty is exacerbated by the significant spatial and temporal variability. Therefore, to capture the magnitude of SGD, a variety of techniques and measurements, applied over multiple periods, is needed. Here, we combine several geophysical methods to detect zones of fresh submarine groundwater discharge (FSGD) in the intertidal zone, upper beach, dunes, and shallow coastal area. Both terrestrial electrical-resistivity tomography (ERT; roll-along) and marine continuous resistivity profiling (CRP) are used from the shallow continental shelf up to the dunes and combined with frequency domain electromagnetic (FDEM) mapping in the intertidal zone. In particular, we apply an estimation of robust apparent electrical conductivity (rECa) from FDEM data to provide reliable lateral and vertical discrimination of FSGD zones. The study area is a very dynamic environment along the North Sea, characterized by semi-diurnal tides between 3 and 5m. CRP is usually applied in calmer conditions, but we prove that such surveys are possible and provide additional information to primarily land-bound ERT surveying. The 2D inversion models created from ERT and CRP data clearly indicate the presence of FSGD on the lower beach or below the low-water line. This discharge originates from a potable freshwater lens below the dunes and flows underneath a thick saltwater lens, present from the dunes to the lower sandy beach, which is fully observed with ERT. Freshwater outflow intensity has increased since 1980, due to a decrease of groundwater pumping in the dunes. FDEM mapping at two different times reveals discharge at the same locations, clearly displays the lateral variation of the zone of discharge, and suggests that FSGD is stronger at the end of winter compared to the beginning of autumn. ERT, CRP, and FDEM are complementary tools in the investigation of SGD. They provide a high-resolution 3D image of the saltwater and freshwater distribution in the phreatic coastal aquifer over a relatively large area, both off- and onshore.. © Author(s) 2020.
语种	英语
scopus关键词	Aquifers; Beaches; Coastal zones; Electric conductivity; Electric discharges; Frequency domain analysis; Groundwater pollution; Groundwater resources; Mapping; Submarines; Surveys; Apparent electrical conductivity; Complementary tools; Dynamic environments; Electrical resistivity tomography; Frequency domain electromagnetic methods; Fresh submarine groundwater discharges; Spatial and temporal variability; Submarine groundwater discharge; Discharge (fluid mechanics); discharge; electromagnetic method; groundwater; intertidal environment; underwater environment
来源期刊	Hydrology and Earth System Sciences
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/159353
作者单位	Paepen, M., Laboratory for Applied Geology and Hydrogeology, Department of Geology, Ghent University, Krijgslaan 281-S8, Ghent, 9000, Belgium; Hanssens, D., Research Group Soil Spatial Inventory Techniques, Department of Environment, Ghent University, Coupure links 653, Ghent, 9000, Belgium; De Smedt, P., Research Group Soil Spatial Inventory Techniques, Department of Environment, Ghent University, Coupure links 653, Ghent, 9000, Belgium; Walraevens, K., Laboratory for Applied Geology and Hydrogeology, Department of Geology, Ghent University, Krijgslaan 281-S8, Ghent, 9000, Belgium; Hermans, T., Laboratory for Applied Geology and Hydrogeology, Department of Geology, Ghent University, Krijgslaan 281-S8, Ghent, 9000, Belgium
推荐引用方式 GB/T 7714	Paepen M.,Hanssens D.,De Smedt P.,et al. Combining resistivity and frequency domain electromagnetic methods to investigate submarine groundwater discharge in the littoral zone[J],2020,24(7).
APA	Paepen M.,Hanssens D.,De Smedt P.,Walraevens K.,&Hermans T..(2020).Combining resistivity and frequency domain electromagnetic methods to investigate submarine groundwater discharge in the littoral zone.Hydrology and Earth System Sciences,24(7).
MLA	Paepen M.,et al."Combining resistivity and frequency domain electromagnetic methods to investigate submarine groundwater discharge in the littoral zone".Hydrology and Earth System Sciences 24.7(2020).