an Estuary
it is an estuary. This is also called a river mouth and delivers the spring water to the sea.
mouth
The mouth of a river is where it empties into another river, a lake, a sea, or an ocean.
River mouth and your mouth, Isn't it?
mouth
The name given to soil deposited at the mouth of a river is called silt. The mouth of a river is called a delta.
Generally, the mouth of a river is found where it empties into another river, a lake, reservoir or ocean. A large river's mouth can cover a massive area.
Tributary. The Missouri river is a tributary of the Mississippi river.
Usually it would be an estuary.
Delta.
Delta