Geological Society of America

T150 Applications of Geophysics to Solve Near-Surface Geological Problems

Tuesday, 11 October 2022
8:00 AM - 12:00 PM
502

GROUNDWATER AQUIFER DELINEATION USING ELECTRICAL RESISTIVITY TOMOGRAPHY AND VERTICAL ELECTRICAL SOUNDING

Paper number: T150-3
Program: Technical Sessions
Time: 8:20 AM – 8:35 AM

Authors

Md Lal Mamud Presenting Author
University of Mississippi, Oxford, MS
Robert M. Holt
University of Mississippi, Oxford, MS
Craig J. Hickey
University of Mississippi, Oxford, MS
Gregg Davidson
University of Mississippi, University, MS
Leti T. Wodajo
University of Mississippi, Oxford, MS
Parsa Bakhtiari Rad
University of Mississippi, Oxford, MS
Md Abdus Samad
University of Mississippi, Oxford, MS
Elsie Buskes
University of Mississippi, Oxford, MS
Md Ilias Mahmud
University of Mississippi, University, MS

Abstract

University of Mississippi Field Station (UMFS) in Mississippi is a multidisciplinary natural research and educational facility. The Meridian Sand aquifer is underlain by a clay Wilcox group and is the main source of groundwater within the facility. The aquifer varies from artesian to unconfined within a very short distance. Electrical resistivity geophysical surveys provide dense spatial data that can be used to identify numbers of sedimentary layers, determine their thickness and map an aquifer. In this study, Vertical Electrical Soundings (VES) and Electrical Resistivity Tomography (ERT) surveys were conducted to map the aquifer within the facility. VES data was collected using the Wenner array with a maximum A-spacing of 40m centering the monitoring well MMRI-BFS-1. Sedimentary layers were identified in this location by analyzing the cumulative plot of the VES data for the inversion. And, the inverted layered resistivity model of the VES data shows the top and bottom of the aquifer at 7.5m and 22m respectively. Data for the three ERT profiles were collected along and across the Bay Spring Flood Plain at the site to determine the extent of the aquifer. The mixed Dipole-Dipole and Strong Gradient array types with 2 m electrode spacing were adopted to collect ERT data. Data for the two 334m long ERT profile-2 and profile-3 were collected with a roll along of 50% overlapping. The finite element method and Cholesky Decomposition solver with Dirichlet boundary conditions using EarthImager 2D were used to invert ERT data. The inverted ERT profile-2 was calibrated with a new borehole log to delineate the aquifer. The ERT profile-2 and profile-3 show the aquifer is confined and pinches out on the southern and eastern sides and has a maximum thickness of about 33m under the Flood Plain close to the old shed. The ERT profile-1 shows the aquifer changes from confined to unconfined on the northern side of the valley. This study delineates the vertical and horizontal extent of the aquifer within the UMFS facility; and provides the electrical conductivity distribution of the subsurface, which will be used as an input to model Streaming-Potential to understand the hydrogeological conditions better.

Geological Society of America Abstracts with Programs. Vol. 54, No. 6

doi: 10.1130/abs/2022AM-382664

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