Combined Inversion of Land and Marine Electrical Resistivity Tomography for Submarine Groundwater Discharge and Saltwater Intrusion Characterization. Issue 3 (3rd February 2020)

• Record Type: Journal Article
• Authors: Hermans, T.; Paepen, M.
• Is Part Of: Geophysical research letters. Volume 47:Issue 3(2020)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2020-02-03
• Subjects: electrical resistivity tomography -- combined inversion -- saltwater intrusion -- submarine groundwater discharge; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1029/2019GL085877
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: Electrical resistivity tomography (ERT) is particularly suited for the characterization of saltwater intrusion and submarine freshwater discharge, given its sensitivity to the electrical conductivity of pore water. A comprehensive survey might combine land ERT collected during low tide and marine ERT acquired with lower sensitivity due to the presence of a seawater layer, most often, inverted separately. In this contribution, we propose a new methodology to jointly invert land and marine ERT acquired along a same profile, bringing them to a common situation at high tide. We first estimate the electrical resistivity distribution under the land profile. Then, we compute a corrected data set for land ERT, simulating a data set collected with the same level of water as the marine ERT. Finally, both land and marine ERT data sets are inverted jointly. We show that the approach allows to better image the freshwater/saltwater distribution across the shoreline. Plain Language Summary: Freshwater aquifers are essential to provide drinking water to the growing World's population. In coastal areas, groundwater resources are thus under pressure, and many coastal aquifers are endangered by the vicinity of seawater. Studying this phenomenon is important but difficult because it takes place at the interface between land and sea. Most often, scientific investigation techniques applied on land and at sea require different processing. This makes their joint interpretation difficult. One of the available techniques to study freshwater and saltwater in aquifers is electrical resistivity tomography (ERT). Marine ERT is less sensitive because it is acquired at sea, but it can still bring relevant information. In this contribution, we develop a new methodology to allow the joint interpretation of land and marine ERT. This allows us to provide a common image of the freshwater/saltwater interface, which can be further used by scientists or authorities to better manage coastal aquifers. Key Points: A new methodology for the combined inversion of land and marine ERT data is proposed Land ERT data are first inverted alone and corrected to account for the water layer present in marine ERT A combined inversion with marine and corrected land ERT, constrained by the resistivity distribution calculated from land ERT, is performed