Effects of Turbulent Ground-Water Flow on Hydraulic Heads and Parameter Sensitivities in Preferential Groundwater Flow Layers within the Biscayne Aquifer in Southeastern Florida

The effect of turbulent groundwater flow on hydraulic heads and parameter sensitivities was examined for the Biscayne aquifer in southern Florida using the Conduit Flow Process (CFP) for MODFLOW-2005. Turbulent flow was spatially extensive in preferential groundwater flow layers with mean void diameters equal to about 3.5 centimeters, groundwater temperature equal to about 25 degrees Celsius, and critical Reynolds numbers less than about 400. Turbulence either increased or decreased simulated heads from laminar elevations. Specifically, head differences from laminar elevations ranged from about -18 to +27 centimeters, and were explained by the magnitude of net flow to the finite-difference model cell. Turbulence also influenced the sensitivities of model parameters. Specifically, the composite-scaled sensitivities of horizontal hydraulic conductivities decrease by as much as 70% when turbulence was removed. Resultant hydraulic head and sensitivity differences due to turbulent groundwater flow highlight potential errors in models which assume laminar flow in an equivalent porous-media having uniformly distributed void spaces.