Modeling Phosphorus Dynamics in a Shallow Lake During an Episodic Event

Wind, current, suspended sediment, dissolved oxygen (DO), pH and phosphorus data were collected in Lake Okeechobee, a shallow lake in south Florida, during a storm event in early 1993. Measured field data indicate that wind and wind-generated waves are major factors responsible for sediment resuspension in the lake. Data also show that soluble reactive phosphorus (SRP) and total dissolved phosphorus (TDP) were inversely-correlated with the DO concentration in the water column. This paper focuses on the use of a vertical one-dimensional model coupling phosphorus dynamics with hydrodynamics and sediment transport processes to simulate the observed episodic event. Model simulations confirmed that resuspension of sediments occurred during the episodic event, with the subsequent increases in phosphorus concentrations. Model results suggest that release of SRP from suspended sediment particles increases as the DO concentration in the water column decreases. By fitting simulated results with field data, an empirical formula describing the effect of the DO concentration on the release of inorganic phosphorus from resuspended sediments has been obtained. Further research to elucidate the detailed mechanism is recommended.