noun
sluice gate; water gate; flood gate
A gate or valve that controls water flow, typically in a canal, dam, or river. The term covers sluice gates, lock gates, and flood gates.
大雨のため、水門を開けて放流した。
Due to heavy rain, they opened the sluice gate to release water.
運河の水門で水位を調節する。
They adjust the water level with the canal's lock gate.