Hydrodynamic and Eutrophication Modeling for a Tidal Marsh Impacted Estuarine System Using EFDC

A hydrodynamic and water quality model was developed to simulate the fate and transport of nutrient, along with eutrophication dynamics in the estuarine system of Mispillion Creek and Cedar Creek, Delaware. The Environmental Fluid Dynamics Code (EFDC) was used as the computational framework for the hydrodynamic and water quality simulation. The grid of the EFDC model for the Mispillion and Cedar creeks covers the main stems of the two rivers, the surrounding tidal marsh areas, and further extends into the Delaware Bay to represent the open boundary condition. Tidal elevation data were obtained from NOAA station 8555889 near Brandywine Shoal Light, Delaware Bay to configure the downstream open boundary. A watershed model was developed based on the Loading Simulation Program in C++ (LSPC) to simulate the flows and pollutant loading for feeding into the EFDC model at locations along the rivers and tidal marsh to form the primary external driving force of the system. The hydrodynamic model simulates circulations, temperature, and salinity in the system, and the water quality simulates the fate and transport of organic and inorganic nitrogen, phosphorus, organic carbon, dissolved oxygen (DO), and phytoplankton in the system.