Three-Dimensional Modeling of Sediment and Phosphorus Dynamics in Lake Okeechobee, Florida: Spring 1989 Simulation

Lake Okeechobee is a large and shallow freshwater body in south Florida. Due to the shallowness of Lake Okeechobee, the nutrient dynamics are strongly influenced by hydrodynamic processes (circulation and windinduced waves) and sediment transport processes. To study water quality and the effects of hydrodynamic and sediment transport processes on nutrient dynamics in the lake, a three-dimensional simulation system that closely couples hydrodynamic and sediment transport processes with nutrient dynamics was developed and used. In this paper, we present a three-dimensional, coupled hydrodynamics-sediment-nutrient model for Lake Okeechobee. The coupled model was used to simulate a four-week survey conducted in spring 1989 in Lake Okeechobee. By comparing model results to measured field data, it is shown that the coupled model system is able to simulate weekly sediment and phosphorus dynamics in Lake Okeechobee. Model applications demonstrated that the resuspension flux of phosphorus from the lake bottom is significantly higher than the molecular flux during resuspension events and can cause increases of phosphorus concentrations in the water column. Sensitivity runs of the model show that both the advective/diffusive transport and the algal uptake promote the release of phosphorus from suspended sediments and thus affect the phosphorus budget in the lake and the net resuspension flux of phosphorus from the lake bottom.