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

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.