Difference Between Estuary and Delta (with Comparison Chart)

When the river enters the sea or any other watercourse, where the flow of water is slow and cannot further carry the sediment brought by the river, the sediment is dropped at the river mouth and which results in the formation of a delta. It is not exactly same as an estuary, which is a coastal water body, where the river meets the sea or any other watercourse, with brackish water.

In short, the basic difference between estuary and delta is that the former is a tidal mouth of the river, where it meets the sea, whereas the latter is nothing but the wetland, formed as a result of the accumulation of sediments carried by the river when it joins a standing waterbody. So, let’s take a read of this article to know more differences on these two.

Comparison Chart

Basis for Comparison	Estuary	Delta
Meaning	Estuary refers to the waterbody, along the coast, that are formed when fresh water of river meets salt water of ocean.	Delta connotes a landform that is formed by river-borne sediments deposited at the river mouth when it joins the sea.
Rivers	Narmada and Tapi form estuary.	Mahanadi, Godavari, Krishna, Cauvery, Ganga and Brahmaputra form delta.
Shape	Funnel	Triangular
Tide	High tides	Low tides
Region	Region near estuary are not fertile.	Delta are fertile lands.
Suitable for	Fishing activity	Agriculture activities

Definition of Estuary

The estuary can be understood as the coastal waterbody of one or more rivers that links to the sea or ocean. It is partially enclosed by land and contains brackish water, i.e. the mix of fresh and saltwater. In short, it is an area where tides flow in and out, and the river becomes wider and slowly converges the sea. It meanders to meet the sea. It may also be called as bay, lagoon and slough.

Depending upon the location and climate, the size and shape of the estuary may differ. In addition to this, the water level and salinity varies with tides.

Definition of Delta

Delta is defined as the landform, created out of deposition of sand, clay and slit, brought by the river, as the river enters another river, sea, ocean, lake, etc. It occurs where the river joins a larger watercourse whose flow of water is slow and is not able to transport the supplied sediment and leaves it at the river mouth which results in the formation of the delta.

Delta is build up by continuous deposition of sediments, which makes the water shallow, causing the landform to rise above the sea level. A delta is divided into four parts, i.e. subaqueous, subaerial, lower delta plain, upper delta plain.

Key Differences Between Estuary and Delta

The difference between estuary and delta are discussed in the points given below:

By estuary, we mean a semi-enclosed waterbody, comprising of brackish water. It is a place where the river meets the sea. On the other hand, the delta is defined as the wetlands, that is formed when a fast moving river joins a slow-moving water body, and thus empty the sediments at its mouth.
In India, rivers like Narmada and Tapi forms estuary, whereas Delta is formed by the Mahanadi, Godavari, Krishna, Cauvery, Ganga and Brahmaputra rivers.
The estuary is like funnel-shaped, the mouth of a river from where the tides move in and out. Conversely, Delta is a triangular land at the river mouth travelled across by its distributaries.
Rivers that encounter high tides are more likely to form estuary. In contrast, the delta is formed when the rivers witness low tides.
The land of the delta is fertile in nature. As against, the area nearby estuary is not fertile in nature.
Delta is good for agricultural activities, while fishing activities are suitable in estuary regions.

Conclusion

While an estuary is a semi-enclosed body of water, where river meets the ocean, the delta is a low-lying plain, formed by the accumulation of alluvium. There is four major type of estuaries which are drowned river valley estuary, bar-built estuary, fjord estuary and tectonic estuary. On the contrary, various types of delta include wave-dominated delta, tide-dominated delta, Gilbert delta, tidal-freshwater delta, inland delta and mega-delta.