What Is the Meaning of Brackish Water?

What Is the Meaning of Brackish Water?
Water described as "brackish" contains a blend of fresh- and saltwater. While found in a number of natural and human-induced environments, brackish water is most common in estuaries.
 

Salinity

According to the National Oceanic and Atmospheric Administration, brackish water has a salinity--a measure of dissolved salts--between 0.5 and 35 parts per thousand.

 
 

Estuaries

In a coastal estuary, the surge of freshwater moving out of the lower river, the differing densities of fresh and saline water and the cyclical influence of the tides causes the mixing of currents. Because freshwater is less dense than saltwater, the river's freshwater moves toward the sea atop the marine bottom currents coming in. The freshwater layer usually mixes somewhat with the saltiness below to produce a brackish current.

Water Mixing

The exact type of estuary circulation varies for a variety of reasons, including seasonal differences in river discharge. For example, as M. Grant Goss describes it in Oceanography, the movement of saltwater up the Columbia River is more substantial during the summer and autumn dry-season when the river is moving slowly. When the Columbia is moving quickly, saltwater wedges only minimally into the river mouth.

Other Examples

Besides river mouths, other bodies of water can be brackish. Two notable examples are the Black and Baltic seas of Eurasia.

 

Article Written By Ethan Schowalter-Hay

Ethan Schowalter-Hay is a writer and naturalist living in Oregon. He has written for the "Observer," the Bureau of Land Management and various online publishers. He holds a Bachelor of Science in wildlife ecology and a graduate certificate in geographic information systems from the University of Wisconsin.

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