Difference between Delta and Estuary

They are natural geographic structures, bodies of water used by numerous animal species and that are related to each other because they are formed by rivers. Despite this, they present notable differences between them.


It is a type of geographical accident that occurs at the mouth of a river due to the fluvial sediments that are deposited there. The deposits of the large rivers cause the division of the river into multiple arms that form active and inactive channels.

One of the best known deltas is that of the Nile River and from this comes the term “delta” because its mouth had a very triangular shape, resembling the Greek letter delta. Deltas are formed by sedimentation in a soil space that can take a triangular shape. They cause a sharp reduction in the speed of the water flow.

delta types

  • Homopycnic flow delta.
  • Hyperpycnic flow delta.
  • Hypopycnic flow delta.


Estuaries are the mouth, in the sea, of a very wide and deep river. It exchanges salt water and fresh water due to the tides. It is made up of a single wide funnel-shaped arm with beach on both sides. In these areas, the withdrawal of water allows some plants to grow. An estuary is a geographical accident formed by the mixture of fresh and salt water.

It is generated by the entry of seawater during high tide, retaining the waters of the river. Meanwhile, during low tide, the waters return to the sea and ocean. This contributes to the cleaning of the channel, leaving areas with marshes.

Differences between delta and estuary

  • Deltas and estuaries are the two forms of mouth of rivers and seas in the oceans. They differ by tides and their shape.
  • If a tide is very strong, an estuary is formed. Because the power of the tides prevents the formation of sediments.
  • Deltas form in large rivers where the water is not affected by the tides and consequently sediments form.

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