Want to Learn More? Estuaries Defined Freshwater Estuaries Estuary Classification Estuaries are Unique and Important Places

Although freshwater estuaries do not contain saltwater, they are unique combinations of river and lake water, which are chemically distinct. Unlike brackish estuaries that are tidally driven, freshwater estuaries are storm-driven. In freshwater estuaries the composition of the water is often regulated by storm surges and subsequent seiches (vertical oscillations, or sloshing, of lake water). While the Great Lakes do exhibit tides, they are extremely small. Most changes in the water level are due to seiches, which act like tides, exchanging water between the river and the lake. Stratification and mixing of water in freshwater estuaries is also due to changes in temperature differences between stream water and lake waters. The shallow waters of streams responds quicker to changes in temperature changes than deeper lake waters. These changes affect the temperature of the water, its pH, dissolved oxygen and the salinity of the water of the two water bodies, thus influencing the chemistry of this type of estuarine system.

An example of a freshwater estuary can be found on the south-central shore of Lake Erie in Erie County, Ohio and it is called the Old Woman Creek Reserve. The Old Woman Creek National Estuarine Research Reserve is part of a national network of coastal reserves established as living laboratories for long-term scientific research and estuarine education.