upstream control

例句：

1. 1. The upstream control measures were designed to prevent pollution in the river.
   上游控制措施旨在防止河流污染。
2. 2. The upstream control system is crucial for maintaining water quality in the region.
   上游控制系统对于维护该地区水质至关重要。
3. 3. The upstream control measures have been effective in reducing air pollution in the city.
   上游控制措施已经有效地减少了该市的空气污染。