upper level

Pollution at the upper level of the river has made swimming unsafe downstream.

河流上游的污染使下游游泳变得不安全。

The company is trying to find cheaper materials from the upper level of the supply chain.

这家公司正试图从供应链上游寻找更便宜的材料。

We live near the upper level of the stream, so the water here is always clear.

我们住在溪流上游附近，所以这里的水一直很清澈。