Using Density-Dependent Numerical Models to Evaluate Regional Groundwater Flow Patterns in South Florida

A variable-density groundwater model was developed for the southern half of Florida as part of a regional study to predict the effects of planned aquifer storage and recovery operations. A persistent problem with the model development was that simulated heads in the southern part of the Florida peninsula were consistently less than observed values. Six tests were performed with the numerical model to try and identify the most likely causes of the discrepancy. The tests included explicit representation of (1) permeable fracture zones, (2) regional horizontal anisotropy, (3) low permeability deposits on the ocean floor, (4) disequilibrium from past sea-level stands, (5) increased hydraulic connection through confining units, and (6) the effects of pressure and temperature on fluid density and viscosity. Test results suggest that combining (2) and (6) provides the best match with the observed heads. Future efforts will focus on improving models of the regional flow system.