Electronic Theses and Dissertations

Joel Pierce

Date

2022

Document Type

Thesis

Degree Name

Master of Science

Department

Civil Engineering

Committee Chair

Brian Waldron

Committee Member

Farhad Jazaei

Committee Member

Charles Camp

Abstract

Numerical groundwater modelers often encounter challenges in implementing and computing regional unconfined aquifer models that match real-world water table undulations and address localized areas of drying/rewetting. A common conservative assumption in such models 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.

Comments

Data is provided by the student.

Library Comment

Dissertation or thesis originally submitted to ProQuest.

Notes

Open access

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