The faculty, staff, and graduate and undergraduate students of GWI integrate research and applied ground water science across several disciplines.  Current collaborators include the Herff College of Engineering, the Department of Earth Sciences (DES) and the Center for Earthquake Research and Information (CERI)

In conducting research, current technology is used and as well as new methods developed to obtain more accurate information.  As research progresses, GWI’s aim is to develop technology and methods that can be used elsewhere, not just in the Mid-South region.

Two key areas of GWI’s research as it relates to the vast aquifer system that serves the Mid-South area are overconsumption of ground water and contamination of ground water.

  Current Research

  Water Sampling at Old Shelby County Landfill

Researchers from the GWI in cooperation with Shelby County government are completing their water-sampling event on wells at the old Shelby County landfill at Shelby Farms.  They are looking to see how underground leakage from the landfill called leachate is leaving the site and what threat the contaminated water may pose to the Memphis aquifer, which is the primary source of drinking water for Shelby County.  Future work will include collection of resistivity data for a creation of a 3-D subsurface model of the leachate plume.  Watch a video on this topic.

  Geologic Modeling

Geologic modeling of the region has typically involved significant extrapolation and been done by examining paper geophysical well logs, geologists logs, and outcrop belts.  Modern geologic modeling techniques allow similar modeling techniques, but in a digital format that allows reassessment of individual well logs once they are compared.  Not only does this improve the robustness of the model, but its validity.  This also allows the direct comparison of well logs quantitatively.  For example, GWI can directly compare the well log responses in different wells to note character changes in the formations that may have led to misinterpretations in past modeling endeavors where digital data was not available.  This modeling encompasses the entire northern Mississippi embayment and new data is added as it become available.  GWI is using this data to build high-resolution models of smaller subsets whereby GWI can extract out individual stratigraphic layers that are missed in typical formation level mapping.

  Well Logging Database

The expanding GWI well log library consists of approximately 18,000 well logs composed of geophysical, geologist, drillers, and penetration logs.  These well logs are being located and added into an interactive database for researchers in the area.  Pertinent well header information such as depth, date drilled/logged, elevation, source of data, type of data, image name, and other pertinent information are recorded within the database, allowing for rapid assessment.  Additionally, GWI is scanning these well logs and adding them into a server-based GIS repository where the digital versions can be readily accessed and utilized.

  Davis Well Field Project

The Davis well field is in close proximity to the Mississippi River.  Several authors have postulated that there is a breach or window in the protective clay layer protecting the Memphis aquifer.  GWI is currently deploying transducers in and around the Davis well field that will allow GWI to monitor water levels in the alluvial aquifer, Memphis aquifer, and the Fort Pillow aquifer.  From these results and comparisons with the Mississippi River level, GWI will be able to ascertain if there is interaction with the shallower aquifer and the Memphis aquifer as well as get an idea on the water levels for the deeper Fort Pillow aquifer.  This effort to model the potentiometric surfaces in detail will be combined with a regional effort GWI is undertaking to strategically place transducers around the Memphis area to better understand and monitor water levels in “real-time.”

  Ground Water Age-Dating

Due to concern regarding potential for contaminated or poor quality water infiltrating into the Memphis aquifer in Shelby County, a project was initiated with finding from the Shelby County Department of Health in 2000 to investigate the source of modern water (< 60 years old) entering the Memphis aquifer.  Over the past 11 years more than 145 samples from approximately 80 production wells in the Memphis area have been sampled and analyzed for environmental tracers (mainly 3H, tritium) used for determining the presence and quantity of modern water.  Several MLG&W well fields (Allen, Davis, Lichterman, McCord, and Sheahan) have significant quantities of modern water leaking from nearby shallow aquifer and stream water sources into the Memphis aquifer.  Production wells in other municipalities also show signs of modern water in the Memphis aquifer, especially Collierville.

  Geologic Mapping of the Memphis Sand in Western Tennessee

 Geologic mapping of the Eocene Memphis Sand, the geologic formation comprising the Memphis aquifer, was conducted during 2010 and 2011 in Fayette County, Tennessee, supported by funds from the USGS EDMAP program.  The purpose of the mapping is to determine where the Memphis Sand is exposed at the surface in the recharge area for the Memphis aquifer and what the geologic properties of the exposed Memphis Sand are.  The results indicate that exposure of the Memphis Sand is very limited across the recharge area and that recharge to the aquifer is focused in stream valleys and steep slopes. 

  Ground Water Surface Water Interaction at the Sheahan Well Field

Ground-water research since 1965 has hinted that Nonconnah Creek was a possible source for modern water entering the Memphis aquifer near the Sheahan well field.  A field investigation was conducted in 2004-2006, funded by the USGS Tennessee Water Resources Research Center, to conduct a comprehensive assessment of the hydrologic connection between Nonconnah Creek and the Sheahan well field.  Students measured stream discharge in the creek and water levels in nearby wells in the shallow aquifer over a year and determined that as much as 0.6 million gallons per day, on average, is seeping beneath the creek bed into the underlying shallow aquifer.  Chemical and age-dating results on water from the creek, shallow aquifer and Memphis aquifer all confirm a similar conclusion:  creek water is seeping into the creek bed and flowing in the shallow aquifer at least 2 miles to the center of the well field and draining through a window in the confining unit to the Memphis aquifer.  Ground-water flow modeling results show that water from the creek must re-supply the leakage from the shallow aquifer to the Memphis aquifer.

  Recharge of the Memphis Aquifer

Management of a ground water resource can be pictured as being a box having inputs and outputs.  Outputs from the box (aquifer system) can be considered as ground-water withdrawals through pumping.  In the Mid-South region, there is a good understanding of the demands placed on the ground-water system by pumping.  However, inputs like recharge are not well known, and to properly manage ground-water resources,  recharge rates must be quantified.  Hence, the GWI is conducting recharge research in the aquifer outcrop region where precipitation infiltration replenishes ground water.  GWI is using water tracing within the vadose zone, geochemical modeling, and a water budget analysis to estimate recharge rates.

  Mississippi Embayment Regional Ground Water Study

The University of Memphis’ Ground Water Institute received a congressional earmark in 2006 through the Environmental Protection Agency (EPA) to investigate, in cooperation with Arkansas State University and the University of Mississippi, the sustainability of the Holocene-Tertiary ground-water system within the Mississippi embayment.  The study footprint was over the tri-state corner region of Tennessee, Arkansas and Mississippi.  This investigation was the first phase of a four-phase study.  Conducted in this first phase: (1) hydrogeologic unit boundaries were defined and hydraulic characteristics analyzed; (2) ground-water geochemistry and tracer data from various sources were compiled, outliers were identified, and chemical mixing models were developed; and (3) information on potential recharge sources to the ground-water system were collected.  The publication from this study may be found here.