xiè / hóng / qián / bì / xū / xiān / xià / zhá / yǐ / miǎn / xià / yóu / fā / shēng / wēi / xiǎn

泄洪前必须先下闸，以免下游发生危险。

The sluice gate must be lowered before releasing the floodwater to prevent danger downstream.