noun
distributary; branch (of a river)
A river branch that diverges from the main stream and does not rejoin it, as opposed to a tributary (支流). Used in geography and hydrology.
See also: 分流
この地域では、本流からいくつかの派川が分かれている。
In this area, several distributaries branch off from the main stream.
派川は河口付近でよく見られる地形だ。
Distributaries are a common landform near river mouths.
Compound of 派 (ha, 'branch, faction') and 川 (sen, 'river'). The reading はせん follows standard on'yomi. The term is technical and not commonly used in everyday conversation.