Modeling as a Tool for Nutrient Management in Lake Erie: a Hydrodynamics Study

Coupled physical-biological numerical models are useful tools for understanding the relevant processes and the influence of biota and human activity on the ecological conditions in the lake, and such a suite of models has been used to assess the impact of zebra mussels on the nutrient cycling in the lake. This paper presents the hydrodynamic part of a Lake Erie modeling exercise using the 3D ELCOM model. Validation runs were performed with 1994, 2001, 2002, and 2003 data where vertical thermistor chain data are compared against model calculations and mean circulation patterns are presented for the different runs. The validated model was then used to understand the flushing of the deep water, the internal wave dynamic and the residual circulation. For example, the presence of two gyres in the west-central basin that entrain nutrient-rich western basin and Sandusky Bay water and are probably a key mechanism for retaining externally supplied nutrients in this region, contributing to variability of primary productivity and its spatial distribution in the central basin. External nutrient loads are transported eastward more quickly than would occur without gyres, and would support less extensive phytoplankton development in the west-central basin. The hydrodynamic results will eventually be used as the drivers for future simulations aimed at studying the fate and transport of nutrients.