Application of geophysical methods to enhance aquifer characterization and groundwater-flow model development, Des Moines River alluvial aquifer, Des Moines, Iowa, 2022

Thomas, Judith C.; Spring, Morgan A.; Gruhn, Lance R.; Bristow, Emilia L.

doi:10.3133/fs20233006

Cited by 1 publication

(1 citation statement)

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“…ER has been used to identify the aquifers and aquitards in different geological settings [4][5][6], which is crucial for groundwater management. Defining aquifers and confining-unit boundaries using geophysical methods helps to create better hydrogeologic models for improving groundwater budgets and identifying groundwater contamination flow paths [7][8][9]. Characterizing and identifying a confining unit, especially the layer above a semi-confined aquifer, is critical to prevent contaminants from flowing into an underlying aquifer.…”

Section: Introductionmentioning

confidence: 99%

Identification of Breaches in a Regional Confining Unit Using Electrical Resistivity Methods in Southwestern Tennessee, USA

Hasan,

Larsen,

Schoefernacker

et al. 2023

Water

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Electrical resistivity and borehole data are applied to delineate lithostratigraphic boundaries and image the geometry of confining-unit breaches in Eocene coastal-plain deposits to evaluate inter-aquifer exchange pathways. Eight dipole–dipole array surveys were carried out, and apparent resistivity was inverted to examine the lateral continuity of lithologic units in different water-saturation and geomorphic settings. In addition, sensitivity analysis of inverted resistivity profiles to electrode spacing was performed. Resistivity profiles from Shelby Farms (SF) highlight the effect of varied electrode spacing (2.5, 5, and 10 m), showing an apparent ~0.63 to 0.75 depth shift in resistivity-layer boundaries when spacing is halved, with the 10 m spacing closely matching borehole stratigraphy. Grays Creek and Presidents Island profiles show clay-rich Eocene Cook Mountain Formation (CMF), with resistivity ranging from 10 to 70 Ω-m, overlying the Eocene Memphis Sand—a prolific water-supply aquifer. Resistivity profiles of SF and Audubon Park reveal sandy Cockfield Formation (CFF) paleochannels inset within and through the CMF, providing hydrogeologic connection between aquifers, and clarifying the sedimentary origin of confining-unit breaches in the region. The results underscore the efficacy of the electrical resistivity method in identifying sand-rich paleochannel discontinuities in a low-resistivity regional confining unit, which may be a common origin of breaches in coastal-plain confining units.

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