noun
A mountain range that forms a drainage divide, separating river systems. Used in geography and earth science contexts.
この分水山脈を境に、川の流れが太平洋側と日本海側に分かれる。
This watershed mountain range divides the river flow into the Pacific side and the Sea of Japan side.
分水嶺 refers to a watershed divide in general, often a ridge or line, while 分水山脈 specifically emphasizes a mountain range acting as the divide.
Compound of 分水 (watershed, drainage divide) and 山脈 (mountain range). The exact historical derivation is uncertain; the spelling is conventionally associated with the meaning.