Modeling Winter Circulation in Lake Okeechobee, Florida

Abstract

A time-dependent three-dimensional hydrodynamic model of Lake Okeechobee was validated and used to understand the physical processes associated with vertical mixing in the lake. The lake has relatively uniform water depths in the open water areas, and the localized bathymetry irregularities are small, which enables the Lake Okeechobee Hydrodynamic Model with a grid resolution of 912 x 923 m to represent the hydrodynamic processes reasonably well. This work presents the results of a 7-week simulation that uses measured bathymetry, relative humidity, total solar radiation, wind velocity, inflow, and outflow. Surface elevation, velocity field, and temperature are computed and compared with observed data. Conservation equations for mass, momentum, and temperature transport are solved to provide values for water depth, current velocities, and water temperatures. The statistical comparisons between the simulated and observed results indicate that the model represents the circulation and temperature distribution of the lake very well. The model was run for a 7-week verification period, during which water levels receded because of dry conditions. The model also indicates that well-mixed circulation patterns for the top and bottom layers result from high wind events. Diurnal thermal stratification impacts may result in a two-alyer flow and affect the horizontal dispersion in Lake Okeechobee. The model results indicate that wind is the major driving force of horizontal and vertical water movement; however, during calm periods, geostrophic currents would be significant.