Modification and Recalibration of an Existing Groundwater Model of Shelby County, Tennessee

ABSTRACT Recent updates and recalibration were made to a groundwater model of Shelby County, Tennessee, to simulate groundwater flow dynamics more accurately in and between aquifers and to be utilized for predictive simulations. The modified CAESER‐II model extends the simulation period from 1960 to 2021 and incorporates several improvements: updated hydraulic parameters for the Memphis aquifer, refined aquitard breach characterization, and enhanced historical records for pumping and river stage. The recalibrated model achieved a mean absolute residual (MAR) of 3.31 m across the domain and 3.70 m at the Sheahan well field, demonstrating improved performance over the original CAESER‐I model. Calibrated values for hydraulic conductivity and specific storage fell within literature‐reported ranges, and the average vertical conductivity of breaches (0.076 m/day) closely matched values obtained from core samples and falling head tests. These enhancements enable better simulation of inter‐aquifer leakage and provide utility managers with a robust tool for assessing well field vulnerability and evaluating the risk of contaminant migration through aquitard breaches.