Translation guide
河口 (かこう) is the standard term for estuary, but 入り江 (いりえ) can be used for a small, sheltered inlet that may include an estuary.
The wide part of a river where it meets the sea, with brackish water.
The most common and direct translation for 'estuary'. Used in geography, science, and everyday contexts.
この河口には多くの鳥が集まります。
Many birds gather at this estuary.
河口域の生態系は非常に豊かです。
The ecosystem of the estuary is very rich.
Refers to a small inlet or cove, often where a river meets the sea. More picturesque and less technical than 河口.
河口 (かこう) is the precise geographical term for an estuary. 入り江 (いりえ) is a more general term for a small inlet or cove, which may include an estuary but is not limited to it. Use 河口 for scientific or formal contexts, and 入り江 for descriptive or literary contexts.
That estuary is quiet and beautiful.