263-10 West Tennessee Groundwater: Insights into the Mississippi Embayment aquifers geochemical characteristics

Session: Exploring Groundwater Recharge and Management: Managed Aquifer Recharge and Other Innovative Tools for Water Supply Development and Operations (Posters)

Poster Booth No.: 81

Presenting Author:

Laura Ruhl-Whittle

Authors:

Ruhl-Whittle, Laura Suzanne¹, Hill, Kristi², Hourigan, Amy³, Smith, Spencer⁴, Gratzer, Michael Charles⁵, Kingsbury, James⁶, Ham, Brian⁷

(1) US Geological Survey, Fayetteville, AR, USA; Geosciences Department, University of Arkansas, Fayetteville, AR, USA, (2) US Geological Survey, Nashville, TN, USA, (3) US Geological Survey, Nashville, TN, USA, (4) US Geological Survey, Memphis, TN, USA, (5) US Geological Survey, Collierville, TN, USA, (6) US Geological Survey, Nashville, TN, USA, (7) Division of Water Resources, Tennessee Department of Environment and Conservation, Nashville, TN, USA,

Abstract:

Forty-three percent of Tennessee’s population uses groundwater as their primary source of water for drinking and domestic uses, and in West Tennessee groundwater serves as the predominant source of water. The aquifers in West Tennessee are part of the Mississippi Embayment aquifer system which spans several neighboring states. In recent years, West Tennessee has experienced increases in water demand and water use is expected to continue to increase in coming years. Therefore, it is important to characterize the ambient water quality of major aquifers in West Tennessee to provide a better understanding of the susceptibility of these aquifers to changes in water quality as a result of increases in water use and the overlying land use. The U.S. Geological Survey (USGS) in cooperation with the Tennessee Department of Environment and Conservation (TDEC) established a network of wells to characterize the ambient groundwater quality of the major supply aquifers across Tennessee. In West Tennessee, thirty wells were selected for aquifers in the Holocene alluvium, Cockfield-Jackson Formations, Fort Pillow Sand, Memphis sand, Coffee Sand, Eutaw Formation, and McNairy Formation. The number of sites selected and sampled in each aquifer was based on the amounts of groundwater use and the areal extents of the aquifers, as well as, well depths, well types, and whether sites had historical water-quality data to determine if water quality has changed over time. Samples were analyzed for major ions, trace elements, nutrients, dissolved organic carbon, volatile organic compounds, tritium, and a subset of wells were sampled for E. coli and pesticides.  The dataset evaluated includes the 30 recently collected samples, and over 200 samples from 1990 to 2025  from various studies to provide an opportunity to identify if and where water quality changes have occurred in these aquifers. Differences in major ion geochemistry within each aquifer was a function of location of wells along regional flow paths and distance from the recharge and outcrop areas of each aquifer.  Water types and concentrations of redox sensitive constituents (redox conditions) varied among the aquifers. Characterization of these aquifers will provide a better understanding of the age, movement, and quality of the groundwater for this region to allow better planning and management of the groundwater resources of West Tennessee.

 

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

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