turn back flow

例句：

1. 1.The river turns back flow as it reaches the sea.
   这条河流在到达大海时会逆流而上。
2. 2. The water turned back flow caused a flood in the town.
   水流逆流导致城镇发生洪水。
3. 3.The engineer designed a system to turn back flow and improve water quality.
   工程师设计了一个系统来逆转水流并改善水质。