I think it MIGHT be a basin.... I could be wrong.
river basin
Basin
A river system that operates inside a drainage basin. A drainage basin is the area of land drained by a river and its tributaries.
Delta
The area of land drained by a river is called a "catchment area". It is so-called because is the the area that catches the precipitation (rainfall).Another term is "river basin", but this is less specific.(The geographical term, "catchment area", is often used to describe the area served by, say, a school or hospital).
An area drained by a river or river system is called a drainage basin.
an area drained by a river is called pooo lol
river basin
a watershed, also called a drainage basin, is an area drained by a river.
River Basin
the land drained by a river system
Basin
Basin
This is its catchment - surrounded by its watersheds.
Drainage basin.
the Mississippi.
the Mississippi.