ABSTRACT
The backwater river reaches draining into the Great Lakes are considered by some to be estuaries. The characteristics of estuaries are often controlled by the differences in the chemical and biological characteristics of freshwater and seawater and the degree of mixing that occurs. The density differences between freshwater and seawater cause estuarine mixing to be distinctly different from mixing in freshwater lakes or oceans. In the zone of the estuary dominated by riverine flows, the salinity distribution is relatively low and constant from top to bottom. Down-estuary, at the edge of the salt wedge, the velocity is greatest at the surface and then approaches zero near the bottom. Estuary geomorphology strongly affects the transport of pollutants and ultimately impacts water quality characteristics. The majority of estuaries in the contiguous United States are of the drowned-river or coastal-plain type. Examples include Chesapeake Bay and the Delaware Estuary. The stratification parameter is much less sensitive to tidal variations than the circulation parameter.
