Modeling Water Quality in Indian River Lagoon, Florida

Indian River Lagoon (IRL) is a long, narrow and shallow coastal lagoon located on the east coast of Florida. It is a nationally renowned aquatic ecosystem that supports tremendous biodiversity and provides recreational and commercial fishing resources as well. The St. Johns River Water Management District (SJRWMD) is charged with the responsibility of protecting this important coastal water body by developing seagrass-based Pollutant Load Redcution Goals (PLRGs). The development of justifiable PLRGs involves identification of the pollutants impacting the health and distribution of seagrass in the IRL and estimation of the response of the IRL to reductions of pollutants. To aid in these efforts, SJRWMD initiated and funded the University of Florida (UF) to develop a CH3D (Curvilinear Hydrodynamic Three Dimensional, based IRL specific integrated estuarine model. The integrated model, consisting of hydrodynamic, wave, suspended sediment transport, light attenuation and eutrophication model components, allows the examination of physical, chemical and biological interactions within the IRL system. UF has calibrated the model using one-year data. In this study, a two-year simulation was performed using HSPF (Hydrologic Simulation Program Fortran) predicted nutrient and sediment loads as boundary conditions. Simulated dissolved oxygen, chlorophyll_a and nutrients were compared with observed data in the IRL. Nutrient budgets computed using the model show the possible importance of nutrient recycling within sandy bottom sediments.