estuary n : the wide part of a river where it nears the sea; fresh and salt water mix

English

Noun

1. Coastal water body where ocean tides and river water merge.
2. An ocean inlet also fed by fresh river water.

Derived terms

• Estuary English

Translations

• Finnish: murtovesi (alue)
• Italian: estuario
• Welsh: aber
• Japanese: 河口(かこう kakō)

An estuary is a semi-enclosed coastal body of water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries are often associated with high rates of biological productivity.

An estuary is typically the tidal mouth of a river (aestus is Latin for tide), and estuaries are often characterized by sedimentation or silt carried in from terrestrial runoff and, frequently, from offshore. They are made up of brackish water. Estuaries are more likely to occur on submerged coasts, where the sea level has risen in relation to the land; this process floods valleys to form rias and fjords. These can become estuaries if there is a stream or river flowing into them. Large estuaries, like Chesapeake Bay and Puget Sound, often have many streams flowing into them and can have complex shapes. Estuaries are often given names like bay, sound, fjord, etc. The terms are not mutually exclusive. Where an enormous volume of river water enters the sea (as, for example, from the Amazon into the South Atlantic) its estuary could be considered to extend well beyond the coast. Estuarine circulation is common in estuaries; this occurs when fresh or brackish water flows out near the surface, while denser saline water flows inward near the bottom. Anti-estuarine flow is its opposite, in which dense water flows out near the bottom and less dense water circulates inward at the surface. These two terms, however, have a broader oceanographic application that extends beyond estuaries proper, such as in describing the circulation of nearly-closed ocean basins. Estuaries are marine environments, whose pH, salinity, and water level are varying, depending on the river that feeds the estuary and the ocean from which it derives its salinity (oceans and seas have different salinity levels). The time it takes an estuary to completely cycle is called flushing time. As ecosystems, the estuaries are under great threat from human activities. They are small, in demand, impacted by events far upstream or out at sea, and concentrate materials such as pollutants and sediments.

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References

arm, armlet, avenue, bay, bayou, belt, bight, blowhole, boca, channel, chute, cove, creek, debouch, door, egress, emunctory, escape, euripus, exhaust, exit, fjord, floodgate, flume, frith, gulf, gut, harbor, inlet, kyle, loch, loophole, mouth, narrow, narrow seas, narrows, natural harbor, opening, out, outcome, outfall, outgate, outgo, outlet, pore, port, reach, road, roads, roadstead, sally port, sluice, sound, spiracle, spout, strait, straits, tap, vent, ventage, venthole, vomitory, way out, weir