If you find pollution at a certain point in a river,would you look at the watershed upstream or downstream to determine its origin?

Question

Quizplus · Accepted Answer

To determine the origin of pollution in a river, it is best to look upstream towards the sources of the pollution. This is because pollutants can get carried downstream by the flow of water, but treating the source is the most effective way to prevent or reduce pollution in the long term.

If You Find Pollution at a Certain Point in a River,would