An area drained by a river or river system is called a drainage basin.
flood plain
Delta
Basin
lake
Basin
Delta
Delta
an area drained by a river is called pooo lol
a watershed, also called a drainage basin, is an area drained by a river.
River Basin
the land drained by a river system
Basin
No, it's a watershed.
This is its catchment - surrounded by its watersheds.