Translation guide
A structure used to release excess water from a dam, reservoir, or canal. In Japanese, the most common term is 余水吐き, but other technical terms exist depending on context.
The most common way to refer to a spillway in everyday or general contexts.
The standard term for a spillway. Literally 'excess water spout'. Used in general and technical contexts.
ダムの余水吐きから水が勢いよく流れ出ている。
Water is gushing out from the dam's spillway.
Often used for larger-scale spillways or discharge channels. Can also mean 'drainage canal' or 'discharge channel'.
大雨でダムの放水路が開かれた。
The dam's spillway was opened due to heavy rain.
A synonym for 余水吐き, used in engineering contexts. Literally 'excess water channel'.
余水路の設計には細心の注意が必要だ。
The design of the spillway requires meticulous attention.
Specifically refers to an emergency spillway used during floods or extreme conditions.
Emergency spillway. Used when the main spillway capacity is exceeded.
非常用余水吐きが初めて使用された。
The emergency spillway was used for the first time.
Emergency discharge channel, often used interchangeably with emergency spillway.
緊急放水路の建設が急がれている。
Construction of the emergency spillway is being rushed.
A spillway that allows water to overflow when the water level exceeds a certain point.
Overflow spillway. Water flows over a crest or weir.
越流式余水吐きは、水位が上がると自然に水が流れ出る仕組みだ。
An overflow spillway is a mechanism that naturally releases water when the water level rises.
Overflow weir, often part of a spillway structure.
越流堰から水があふれ出した。
Water overflowed from the spillway weir.
A spillway where water flows over a side weir into a channel parallel to the dam.
Side channel spillway. A technical term used in dam engineering.
このダムには側水路式余水吐きが採用されている。
This dam uses a side channel spillway.
余水吐き is the most direct translation for 'spillway' and is used specifically for dam overflow structures. 放水路 can refer to any water discharge channel, including spillways, but also drainage canals and floodways. In dam contexts, 余水吐き is more precise.
In casual conversation, 余水吐き may not be widely known. If explaining to a non-specialist, you can describe it as ダムの水を逃がすところ (the place where water is released from the dam).