noun
regulating reservoir; retention basin; balancing pond
Civil engineering term for a pond or basin that temporarily stores stormwater or regulates water flow to prevent flooding and control runoff.
この調整池は大雨のときに洪水を防ぐ役割を果たしている。
This retention basin plays a role in preventing floods during heavy rain.
貯水池 is a general reservoir for water supply or irrigation, whereas 調整池 is specifically for regulating water flow and preventing floods.
Compound of 調整 (regulation, adjustment) and 池 (pond). The term is a modern technical coinage for water management infrastructure.