Thesis Defense Announcement

The College of Arts and Sciences announces the Final Thesis Defense of

Michael Smith

for the Degree of Master of Science

November 8, 2018 at 1:00 PM in Johnson Hall, Room 216

Advisor: Daniel Larsen

Evaluating modern recharge of the Memphis aquifer at the Lichterman well field, Memphis, TN

ABSTRACT: The Lichterman well field is a municipal water plant in Shelby County, Tennessee, vulnerable to vertical seepage of modern (<60 years) groundwater into the underlying semiconfined Memphis aquifer. In order to identify probable recharge pathways and sources of modern water, 11 production wells and 1 shallow monitoring well were sampled for major solute chemistry, 3H, 3He, SF6, and noble gases. Hydrostratigraphic cross sections reveal potential pathways of modern water leakage to the Memphis aquifer adjacent to the well field. Geochemical inverse modeling estimates up to 12% modern water from sampled production wells. Lumped parameter modeling best fit a piston flow model for regional recharge and dispersion model for local recharge through suspected hydrologic windows estimating the fractions of modern water from 15 to 23%. Unconfined conditions in the Memphis aquifer and limited saturation of the overlying shallow aquifer may limit vertical leakage of modern water into the Memphis aquifer.