Imaging artificial salt water infiltration using electrical resistivity tomography constrained by geostatistical data

The geometry and the hydraulic properties of the unsaturated zone is often difficult to evaluate from traditional soil sampling techniques. Soil samples typically provide only data of the upper layers and boreholes are expensive and only provide spotted information. Non-destructive geophysical methods and among them, electrical resistivity tomography can be applied in complex geological environments such as volcanic areas, where lavas and unconsolidated pyroclastic deposits dominate. They have a wide variability of hydraulic properties due to textural characteristics and modification processes suh as compaction, fracturation and weathering. To characterize the subsurface geology below the golf course of Bandama (Gran Canaria) a detailed electrical resistivity tomography survey has been conducted. This technique allowed us to define the geometry of the geological formations because of their high electrical resistivity contrasts. Subsequently, undisturbed soil and pyroclastic deposits samples were taken in representative outcrops for quantifying the hydraulic conductivity in the laboratory where the parametric electrical resistivity was measured in the field. A statistical correlation between the two variables has been obtained and a 3D model transit time of water infiltration through the vadose zone has been built to assess the vulnerability of the aquifers located below the golf course irrigated with reclaimed water.

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MAPPING WATER INFILTRATION OF URBAN SOILS USING ELECTROMAGNETIC INDUCTION AND TIME-LAPSE ELECTRICAL RESISTIVITY TOMOGRAPHY

10.1130/abs/2017am-303606 ◽

2017 ◽

Author(s):

Vince Carsillo ◽

◽

Jonathan Nyquist ◽

Tyler Wong ◽

Laura Toran

Keyword(s):

Electrical Resistivity ◽

Electromagnetic Induction ◽

Urban Soils ◽

Electrical Resistivity Tomography ◽

Time Lapse ◽

Water Infiltration ◽

Resistivity Tomography

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Imaging the extent of saltwater intrusion in the Luy river coastal aquifer (Binh Thuan) using electrical resistivity tomography (ERT)

10.5194/egusphere-egu21-4960 ◽

2021 ◽

Author(s):

Cong-Thi Diep

Keyword(s):

Electrical Resistivity ◽

Coastal Aquifer ◽

Saltwater Intrusion ◽

Electrical Resistivity Tomography ◽

Salt Water ◽

Groundwater Resources ◽

Left Bank ◽

Resistivity Tomography ◽

South Central ◽

Recharge Sources

Imaging the extent of salt water intrusion in the Luy river coastal aquifer (Binh Thuan) using electrical resistivity tomography (ERT)Diep Cong-Thi1,3, Linh Pham Dieu1,3, Robin Thibaut1, Marieke Paepen1, Hieu Huu Ho3,Fr&#233;d&#233;ric Nguyen2, Thomas Hermans1&#160;1Department of Geology,Ghent University, 9000-Gent, Belgium2 Department of Urban and Environmental Engineering,Liege University and Department of Civil Engineering, KU Leuven, B- 4000 Li&#232;ge and 3000 Leuven, Belgium3 Department of Marine Geology, Vietnam Institute of Geosciences and Mineral Resources (VIGMR), 100000 Hanoi, Vietnam&#160; ABSTRACTSeawater intrusion has been one of the most concerning issues of the Vietnam South Central provinces in recent years, especially in the Binh Thuan province which is characterized by a hyper-arid climate. During the dry season extending from November to April, seawater intrudes through estuaries and threatens groundwater resources. The latter are under increasing pressure due to water extraction for agri- and aquaculture. To evaluate the current state of salinity in the shallow coastal aquifer, 21 electrical resistivity tomography (ERT) measurements were collected along the downstream part of the Luy river based on the previous saltwater intrusion boundary which was estimated from water samples collected from shallow boreholes. The data were inverted to get the resistivity distribution of the subsurface and interpreted in terms of salinity. Comparison with well data shows that resistivity values below 6.5 Ohm.m correspond to the presence of saltwater in the aquifers. On the right bank of the river, a higher elevation dune area contains a freshwater aquifer which limits the intrusion of saltwater. On the left bank dominated by lowland areas, saline water fills almost the entire thickness of the aquifer, except locally for small thin freshwater lenses. At larger distances from the sea, the aquifer displays a complex distribution of fresh and saline lenses. Those variations seem to be correlated with the presence of clay lenses, recharge sources and irrigation practices. ERT data also reveals the depth of the rock basement. The geophysical observations show that the extension of saltwater intrusion is much larger and more complex than expected from existing borehole data and is not limited to interaction with the river.KEYWORDS: saltwater intrusion, groundwater, electrical resistivity tomography, Luy river. &#160;*Corresponding Authors. Email: [email protected]; [email protected]; [email protected]; [email protected]; [email protected]; [email protected]; [email protected]