A Comprehensive Multi-Scale, Multi-Technique Field Methodology for
Assessing Aquifer-Stream Interactions along Channelized Lowland Streams
Abstract
Aquifer-Stream Interactions (ASIs) play a critical role in effective
groundwater management, yet their complex dynamics remain poorly
understood in channelized lowland perennial streams. This study presents
a multi-scale, multi-technique investigation of ASIs along two streams
in Shelby County, Tennessee, overlying the confined Memphis aquifer. The
goal is to define a suitable methodology for characterizing ASIs in this
specific hydrological setting, serving as a starting point for
developing a standardized approach. The methodology includes an initial
evaluation of various field techniques, followed by extensive surveys
using potentiomanometers, electromagnetic induction (EMI), vertical
temperature profilers (VTPs), and complementary techniques such as
seepage meters, bank tests, and well-data analyses. Results reveal
distinct hydrogeomorphic behaviors across and along the streams,
challenging the ASI homogeneity notions typically assumed in groundwater
models. Nonconnah Creek exhibited streambed colmation and negligible
hydraulic gradients, resulting in disconnection from the aquifer during
low flows, except for a 300-m losing reach with high downward gradients,
potentially degrading the Memphis aquifer. In contrast, the Loosahatchie
River displays relatively homogeneous streambed properties and small,
upward hydraulic gradients, suggesting uniform ASIs along the surveyed
reaches. EMI proved highly effective for mapping streambed sediments
quickly, while potentiomanometers accurately measure small head
differences critical for understanding ASI dynamics. VTPs were less
practical due to extended data-collection times and vulnerability to
flooding. This study emphasizes the importance of site-specific,
multi-scale investigations using diverse techniques to accurately
characterize ASIs in lowland streams, highlighting the confounding
influences of geological formations, anthropogenic alterations, and
depositional processes on groundwater-surface water interactions. The
findings contribute to refining local water balances, informing
groundwater management strategies, and underscoring the need for
incorporating local-scale field data into regional groundwater models.
The proposed methodology serves as a foundation for developing a
standardized approach for characterizing ASIs in lowland channelized
perennial streams, adaptable for similar stream systems worldwide.