Imaging artificial salt water infiltration using electrical resistivity tomography constrained by geostatistical data (original) (raw)
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Application of Electrical Resistivity Tomography for imaging Seawater Intrusion in a Coastal Aquifer
Acta Geophysica (ISSN 1895-6572, eISSN 1895-7455), 2021
Following previous geoelectrical researches initiated in 2009 for the delineation and characterization of seawater intrusion in a freshwater aquifer of Sarmatian (late Middle Miocene) age, a subsurface imaging survey via 2-D electrical resistivity tomography (ERT) was conducted in 2019 on the outskirts of Vama Veche resort—Romanian Black Sea southern coast. The survey was organized in the framework of a field camp sponsored by the Foundation of the Society of Exploration Geophysicists (SEG)–Tulsa, OK, USA, with participation of teams from the University of Bucharest—Department of Geophysics and the Geological Institute of Romania. A number of eight ERT profiles with N–S, W–E, NNE–SSW, and WNW–ESE orientation and 155–315 m length were imaged with a SuperSting R8/IP instrument (Advanced Geosciences Inc.), using deployments of 32–64 electrodes at 5 m spacing, in Wenner, Schlumberger, and dipole–dipole array configurations. The processing and interpretation of high-resolution ERT data indicated that the seawater intrusion, evidenced as very low resistivity (5–10 Ω m) anomalous zones starting at approximately 45–49 m depth, has advanced at least 500 m inland. The survey results also allowed the identification of a system of fractures or faults with an approximate NW–SE/WNW–ESE and, possibly, N–S orientation, that might have provided potential pathways for saline water intrusion.
IOSR Journals , 2019
Recently, the deterioration of water quality in the coastal areas of Akwa Ibom State, Southeastern, Nigeria due to saltwater infiltration into the freshwater aquifer has become a major concern. In this study, the geophysical method we adopted was the 2-D Electrical Resistivity Tomography (ERT) using resistivity meter and other accessories to obtain the field data. Wenner electrode configuration with electrode spacing ranging from 5 to 200m was used for field measurement and a total of twenty (20) randomly distributed ERT profiles were covered. The modeled field data revealed the resistivities and depth to bottom layer distribution across the study area with predominant lithologies being coastal plain sands. The interpretation showed upper resistivity limit of 232.5 m for medium to fine grained sands; 3,959 m for lateritic sands; 1,580 m for gravelly sands and 185.5 m for sandy/clayey sand and clay soils. The depth of inverse models from the geoelectrical resistivity data obtained in the area revealed significant impact of the saline water in delineated aquifer with very low resistivity values uniquely below 3.24 m. ERT results also shows the lateral invasion and upconing of saline water within the aquifer systems. Both natural and anthropogenic factors are responsible for saline intrusion across the study area. The uniqueness of the techniques and investigations through field data analysis showed the extent a saltwater intrusion into the freshwater aquifer along the interface.
Water, 2021
With the growing population and the adverse effects of climate change, the pressure on coastal aquifers is increasing, leading to a larger risk of saltwater intrusion (SI). SI is often complex and difficult to characterize from well data only. In this context, electrical resistivity tomography (ERT) can provide high-resolution qualitative information on the lateral and vertical distribution of salinity. However, the quantitative interpretation of ERT remains difficult because of the uncertainty of petrophysical relationships, the limitations of inversion, and the heterogeneity of aquifers. In this contribution, we propose a methodology for the semiquantitative interpretation of ERT when colocated well data are not available. We first use existing wells to identify freshwater zones and characterize the resistivity response of clayey deposits. Then, we approximate the formation factor from water samples collected in the vicinity of ERT data to derive a resistivity threshold to interpr...
The first results of a research activity focused on the characterisation of the salt water intrusion along the Ionian coast of the Basilicata region (Southern Italy) are shown and discussed in this study. Along the coast there are many Sites of Community Interest (SCI) subjected to a strong incidence of human activities mainly linked to agriculture and tourism. Primary and secondary salinity of soil are linked to natural factors such as the climate, natural drainage patterns, topographic features, geological structure, distance to the sea and to the indiscriminate exploitation of the soil and groundwater resources. The approach based on the Electrical Resistivity Tomography (ERT) has been adopted to obtain high-resolution electrical images which allow to identify and delineate the geometry of litho-stratigraphic limits, by resistivity contrasts. Then, ERT represents an optimal tool for better reconstructing the geometry of the sea water intrusion front and mapping the areas characte...
Salt-water intrusion mapping by geoelectrical imaging surveys
Geophysical Prospecting, 2000
The geoelectrical imaging method is a tool for mapping the intrusion boundary between fresh water and saline water due to its inherent capability to delineate the lateral changes in pore-water salinity. A new field survey technique that can be used for environmental and geotechnical investigations has been developed. This study evaluates the multiscale survey technique as a tool employed in electrical imaging to detect the salt-water intrusion boundary in Yan, State of Kedah, northwest Malaysia. The technique was incorporated into these surveys, and it has proved to be a robust method for accurately mapping the fresh-water/saline-water boundary. The resulting resistivity sections from these surveys were consistent with both the available geological and borehole information from the area and the previous resistivity surveys conducted by the Geological Survey of Malaysia at those sites.