Difference Between Delta and Estuary

If you have studied geography carefully during your school days, you must remember to come across terms like delta and estuary. Both terms are associated with rivers and large water bodies such as oceans and seas.

Although for a layman, deltas and estuaries would appear to be similar, there are certain important points of differences between the two.

Rivers commence from the mountain ranges and end up at the seas or oceans. At the point where it meets the ocean, the river’s speed diminishes, which restricts the ability of a river to carry various sediments any further.

Key Takeaways

1. A delta is a landform created at the mouth of a river where the river divides into smaller channels and deposits sediment.
2. An estuary is a partially enclosed coastal body of water where freshwater from a river meets and mixes with saltwater from the ocean.
3. Deltas are formed by the deposition of sediment, while the mixing of freshwater and saltwater forms estuaries.

Delta vs Estuary

A delta is a depositional landform formed at the mouth of a river, where sediment carried by the river accumulates and builds up over time, creating a triangular or fan-shaped area of land. An estuary is a partially enclosed coastal body of water where fresh river water mixes with salty ocean water.

However, an estuary is a coastal water body or river that meets a sea or an ocean and forms a transition zone between the two water bodies. In other words, an estuary is formed in regions that experience rift valleys and high tides.

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Comparison Table

Parameter of Comparison	Delta	Estuary
Definition	It is a low triangular-shaped fertile area consisting of alluvial deposits brought in by a river before meeting a large water body.	It is just an area where the fresh water from a river meets the saltwater of seas and oceans.
Formation	Formed when rivers fail to carry along the sediments any further due to reduced current before meeting an ocean or a sea.	It is formed by a tidal bore that gradually erodes the riverbed and also carries the fertile soil or silt to the sea.
Fertility	It is extremely fertile.	It is not very fertile.
Types	Bird’s foot, cuspate, and fan-shaped or arcuate.	Tectonic estuaries, fjord estuaries, and coastal plain estuaries.
Where it is formed	Forms in regions that experience coastal plants and low tides.	Forms in regions that experience rift valleys and high tides.
Suitability for habitation and agriculture	Although it is a flood-prone zone, it is exceptionally suitable for agriculture due to the fertile sediments.	Not suitable for agriculture but is good for wildlife habitats.
Examples	Ganges Delta and Mahanadi Delta.	Baga Creek and Kayamkulam Kayal.

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What is Delta?

Rivers carry loads of soil and other sediments during their long and tiring journey from the mountain ranges to an ocean or a sea.

A delta or most popularly referred to as a river delta is a landform that is created when sediments, carried by rivers, are deposited at the junction of the river and a larger water body such as a sea or an ocean.

Deltas are normally formed at the meeting points of rivers with seas, oceans, lakes, reservoirs, estuaries, and other rivers, which is a rather rare situation.

The shape and size of the delta formed entirely depend upon the mere balance between the receiving water body that may either export or redistribute the sediments and the watershed process that acts as the supplier of the sediments.

Different types of deltas are formed. These include wave-dominated deltas, tide-dominated deltas, gilbert deltas, tidal freshwater deltas, mega deltas, and inland deltas.

Some common examples of deltas include the Amazon delta, Godavari Delta, the Indus River Delta, Rhine Delta, and the Yangtze.

Deltas are extremely fertile, which is why most of the age-old habitats can be found in some of the significant delta regions of the world.

 

What is Estuary?

If you think deltas and estuaries are the same, you must think again!

When you talk about an estuary, it is a limited area of an encircled coastal body of saline water with a minimum of one river flowing into it. It also has a free connection to the sea or the ocean.

It is usually seen that estuaries tend to form a type of transition zone between maritime environments and river environments.

You also need to know that various marine influences, including waves, tides, and inundation of salty water to freshwater flows, influence estuaries.

Due to the mixture of freshwater and seawater, a high level of nutrients is formed both in the sediments and water column. Several estuaries suffer from degeneration due to several factors.

These include deforestation, soil erosion, overfishing, wetland filling, and overgrazing.

Unlike deltas, estuaries are not that fertile and it also has several types that are based on geomorphologies, such as drowned river valleys, fjord type, bar-built or lagoon-type, and tectonically produced.

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Main Differences Between Delta and Estuary

1. Deltas are practically wetlands usually formed when a fast-moving river empties its sediments before joining a slow-moving water body such as a sea, ocean, or lake. On the other hand, estuaries are semi-enclosed water bodies that constitute salty water. It is normally an area where a river merges with a sea.
2. Deltas are normally shaped like a bird’s foot or fan-shaped, whereas estuaries are fjord or tectonic estuaries.
3. Deltas are extremely fertile by nature, which makes them suitable for agriculture, and estuaries are not at all fertile and, thus, not suitable for agriculture.
4. Deltas are formed in regions that experience coastal plants and low tides, whereas estuaries are formed in regions that experience rift valleys and high tides.
5. Examples of deltas include Krishna Delta and Brahmaputra Delta. Examples of estuaries include Thekkumbhagam estuary and Baga Creek.

References

1. https://www.sciencedirect.com/science/article/pii/S0025322705003063
2. https://link.springer.com/article/10.1007/s11625-016-0355-7
3. https://www.jstor.org/stable/208680