noun
headwaters; source of a river
Refers to the upper reaches or origin of a river. Often used in geographical or poetic contexts.
その川の水上は国立公園の中にある。
The headwaters of that river are in a national park.
水上から下流まで、水質を調査した。
We surveyed the water quality from the source to the downstream area.
水源 is a more technical term for a water source, including springs and reservoirs, while 水上 specifically refers to the upper part of a river.
上流 means upstream or upper reaches of a river, focusing on the location rather than the origin point.
Compound of 水 (み, water) and 上 (かみ, upper part). The reading みなかみ is a euphonically changed form of みのかみ.