a ridge of land that separates two adjacent river systems

[ Syn: water parting , divide ]

the entire geographical area drained by a river and its tributaries; an area characterized by all runoff being conveyed to the same outlet; flood control in the Missouri basin

[ Syn: river basin , basin , drainage basin , catchment area , catchment basin , drainage area ]

an event marking a unique or important historical change of course or one on which important developments depend; the agreement was a watershed in the history of both nations

[ Syn: landmark , turning point ]