Major Estuaries in The World

A water body where saltwater & freshwater mixes together.

Classic definition of Estuary

“ An estuary is a semi-enclosed coastal body of water having a free connection with the open sea and within which the sea-water is measurably diluted with fresh water deriving from land drainage”

Types of Estuaries

Classification based on geomorphology:

Classification based on water circulation:

Drowned river valleys:

In places where the sea level is rising relative to the land, seawater progressively penetrates into river valleys and the topography of the estuary remains similar to that of a river valley. Ex: Hudson River, Chesapeake Bay.

Drowned river valleys
Drowned river valleys

Bar-built Estuary

Bar-built estuaries are found in a place where the deposition of sediment has kept pace with rising sea level so that the estuaries are shallow and separated from the sea by sand spits or barrier islands. Ex: Pamlico SoundNorth Carolina.

Bar-built Estuary
Bar-built Estuary

Fjord-type :

This type of Estuaries is characterized by a deep elongated basin that is “U” shaped & a barrier that separates the basin from the sea. They are found along glacier coasts. Ex:Puget Sound.

Fjord-type
Fjord-type

Tectonically produced :

These estuaries are formed by subsidence or land cut off from the ocean by land movement associated with faultingvolcanoes, and landslides.Ex: San Francisco Bay

Tectonically produced
Tectonically produced

 

Based on Water Circulation

Salt wedge:

In this type of estuary, river output greatly exceeds marine input and tidal effects have a minor importance. Ex: Mississippi River.

Partially mixed:

As tidal forcing increases, river output becomes less than the marine input. Here, currently induced turbulence causes mixing of the whole water column. Ex: Chesapeake Bay and Narragansett Bay.

Well-mixed:

Tidal mixing forces exceed river output, resulting in a well-mixed water column and the disappearance of the vertical salinity gradients. Ex: Delaware Bay

Inverse:

Inverse estuaries occur in dry climates where evaporation greatly exceeds the inflow of fresh water. A salinity maximum zone is formed. Ex: Spencer Gulf

Intermittent:

Estuary type varies dramatically depending on freshwater input and is capable of changing from a wholly marine embayment to any of the other estuary types.

Figures of Estuary
Figures of Estuary

Major Estuaries of Asia

  • Phang Nga Bay in Thailand.
  • It is punctuated with islands.
  • A variety of geological forces have fractured the underlying limestone beds and pushed up the 40 steep-sided islands that provide the exotic scenery.

Bay Of Bengal

  • An arm of the Indian Ocean, the Bay of Bengal is 1,300 miles (2,090 km) long and 1,000 miles (1,610 km) wide.The Andaman and Nicobar Islands separate it from the Andaman Sea.
  • The Bay of Bengal’s Sunderbans is the largest estuarine delta in the world.
Bay Of Bengal
Bay Of Bengal

The White Sea

  • The White Sea is an arm of the Barents Sea.
  • It is 580 km (360 mi) long and has an area of 90,000 sq km (30,000 sq mi).
  • The flow of fresh water into the Sea is responsible for relatively low salinity.
  • The southern part is home to the beluga whale.
  • The adult individuals are completely white.
The White Sea
The White Sea

The Gulf of Ob

  • The Gulf of Ob is a bay of the Arctic Ocean
  • It is located in Northern Russia.
  • It is the world’s longest estuary.
  • Also known as Ob Bay
  • It is about 1,000 km (600 mi) long and varies in width from about 50 to 80 km (30–50 mi)
The Gulf of Ob
The Gulf of Ob

Africa Continent


Gabon Estuary

  • The Gabon River or Gabon Estuary is a short wide estuary in the west of Gabon.
  • The estuary empties into the Gulf of Guinea.
  • The estuary is locally known as the Estuaire du Gabon.

The Orange River

  • The Orange River is the longest river in South Africa.
  • The Orange River plays an important role in the South African economy by providing water for irrigation, as well as hydroelectric power.

Europe Continent


The Severn Estuary 

  • The Severn Estuary is the estuary of the River Severn
  • It is the longest river in Great Britain.
  • The estuary has one of the highest tidal ranges in the world — about 50 feet (15 m)
The Severn Estuary
The Severn Estuary

The Thames Estuary

The Thames Estuary
The Thames Estuary

North America Continent


The Chesapeake Bay

  • The Chesapeake Bay is an estuary in the U.S. states of Maryland and Virginia.
  • It is the largest estuary in North America.
  • The bay is approximately 200 miles (320 km) long & 2.8 miles (4.5 km) wide .
  • It shows potential for growth of the native oyster population.
The Chesapeake Bay 
The Chesapeake Bay

Delaware Bay

Delaware Bay
Delaware Bay

The Great Bay

  • The Great Bay is a tidal estuary located in  United States.
  • The bay occupies over 6,000 acres (24 km2)
  • The water surface of Great Bay covers 8.9 square miles (23 km2) at high tide and 4.2 square miles (11 km2) at low tide.

 

Pamlico Sound

  • Pamlico Sound in North Carolina in the US is the largest lagoon along the North American East Coast
  • It extends 129 km (80 miles) long and 24 to 48 km (15 to 20 miles) wide.
  • Once it was used as an atomic bomb test site during the late 1940s and early 1950s.
  • Portions of Pamlico Sound are used as a bombing and training range for Camp Lejeune.
  • The sound also supports local commercial fishing, crabbing, shrimping, clamming, and oystering.
Pamlico Sound
Pamlico Sound

Oceania


   The Spencer Gulf 

  • The Spencer Gulf is the westernmost of two large inlets on the southern coast of Australia
  • The Gulf is 322 km (200 mi) long and 129 km (80 mi) wide at its mouth.
  • The western shore of the Gulf is the Eyre Peninsula.
The Amazon River
The Amazon River
  • Port Jackson is the ria or natural harbor of Sydney, Australia.
  • Its located at the Sydney Opera House & Sydney Harbour Bridge.
  • Many recreational events are based on or around the harbor.

 

South America


  The Amazon River

  • The Amazon River in South America is the largest river by discharge of water in the world and longest in length.
  • The Amazon represents 20% of the global riverine discharge to the ocean.
The Amazon River
The Amazon River

Lagoa dos Patos

  • Lagoa dos Patos is the largest lagoon in Brazil and the largest barrier-lagoon in South America.
  • It is located in the state of Rio Grande do Sul, southern Brazil.
Lagoa dos Patos
Lagoa dos Patos

Factors influencing an estuary

  • Temperature
  • Salinity
  • Nutrients etc

References

 

Written By: Badsha Fahad

 

 

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