upstream lock

例句：

1. 1.The upstream lock prevents the waterfrom flowing downstream.
   上游锁防止水流向下游。
2. 2. The engineer installed an upstream lockto control the flow of water.
   工程师安装了上游锁来控制水流。
3. 3. Theupstream lock is essentialfor maintaining the stability of theriver.
   上游锁对于保持河流的稳定性至关重要。