Dissertation Defense Announcement

Herff College of Engineering announces the Final Dissertation Defense

Joel Pierce

for the Degree of Doctor of Philosophy

January 13, 2022 at 09:00 AM on Zoom - Meeting ID: 863 2822 2996 Passcode: 941018

Advisor: Dr. Brian Waldron

Enhancing groundwater flow modeling and dry cell management of the unconfined aquifer (shallow aquifer) in Shelby County, TN

ABSTRACT: "Numerical groundwater modelers often encounter challenges in the construction and optimization of regional unconfined aquifers in matching real-world water table saturated thicknesses and that address localized areas of drying/rewetting. A common conservative assumption in numerical modeling states that adding greater, real-world detail does not correlate to more substantive model results. The proposed work, however, tests the hypothesis that by incorporating specific areas of greater hydrogeologic complexity into modeling regional sized unconfined aquifers, simulated heads will better match observed local conditions, especially in areas of water loss through aquitard breaches and where dry cells are a natural condition of the system. A series of impact models are used where each model focuses on different additives of complexity such as adjusted recharge, additional tributary streams, and evapotranspiration. Model outcomes are compared against each other, against observed conditions of the shallow unconfined aquifer beneath Memphis, TN, and against a fully calibrated groundwater model of the aquifer systems beneath Shelby County, TN. Results indicate that an increase in stream detail better mimics observed water table undulations. These undulations occur at the same scale as aquitard breaches and minimize cell drying through appropriate gradients and flows surrounding the breaches. Such results in modeling the shallow unconfined aquifer vastly improve models like that of Shelby County, TN, by better representing truer gradients, conveying appropriate quantities of water through breaches and by offering an opportunity for improved contaminant transport modeling from the shallow unconfined aquifer to the deeper, semi-confined Memphis aquifer via such aquitard breaches."