High-Resolution Electrical Resistivity Tomography (ERT) to Characterize the Spatial Extension of Freshwater Lenses in a Salinized Coastal Aquifer

Abstract

High-resolution electrical resistivity tomography (ERT) with electrode spacing of 1 m proved to be an effective methodology to characterize ephemeral, sparse, and discontinuous freshwater lenses within the almost completely salinized shallow aquifer of the low coastal zone near Ravenna. ERT profiles with a vertical resolution of 0.25–0.5 m, once calibrated with groundwater data (water table depth and electrical conductivity) collected in multi-level sampler systems at the same spatial resolution, are reliable and provide repeatable measurements in time. The ERT methodology allows for fast data acquisition over large areas and it also permits the study of the evolution in time of freshwater availability in coastal zones, which is important for local ecosystems and soil resources. This makes high-resolution ERT a valid tool to aid local stakeholders and decision makers to effectively manage freshwater lenses, and guarantee their preservation or augmentation by means of managed aquifer recharge.

Characterizing the Water Storage Capacity and Hydrological Role of Mountain Peatlands in the Arid Andes of North-Central Chile

“…ERT consists of various VES distributed along a profile line, which allows a 2D interpretation of the resistivity distribution [47]. ERT has been successfully used to locate laterally varying geology, such as fracture zones, and to discriminate soil from bedrock [48][49][50].…”

A Large Scale Characterization of the Dielectric Properties of Heterogeneous Layered Rock Salt

“…The method described in this article shows significant improvement compared to others reported in the literature: the work of Lambort et al [38] retrieves thickness of only one layer of material, and one of air; 2-D electrical resistivity tomography allow media characterization with a resolution of 0.25-0.5 m and is also limited to highly irregular or complex geological features [47]; cross-hole GPR, generally requires that the boreholes where the emitters and receivers are inserted to be separated by 10 m at most [48], and in addition, they necessitate a high number of measurements, obtained with either a large number of receivers [49] or very long boreholes where the antennas are moved along [50].…”

“…The results of the fitting algorithm of (9) are limited by the sensitivity of the used VNA in the sense that measurements performed with higher precision instrumentation would lead to a larger number of fully determined layers [more terms would be relevant in (9)]. Note that the other methods, such as 2-D electrical resistivity tomography, allow media characterization with a resolution of 0.25-0.5 m and are also limited to highly irregular or complex geological features [47]. Others, such as cross-hole GPR, generally necessitate that the boreholes where the emitter and receivers are inserted to be separated by 10 m at most [48].…”

Applications of Electrical Resistivity Surveys in Solving Selected Geotechnical and Environmental Problems

“…The method is based on the assumption that soil and rocks, as well as other materials, conduct electricity. As shown by previous studies [12,15,19,21,27], the method is affected by the soil moisture content and water saturation, its porosity and contamination level of water in the soil pores, in particular with salt [15,28,29] and NAPL (non-aqueous phase liquid) compounds [19,30], and change of stress conditions [8,16].…”