Why is the Yarra River so brown?

 https://www.timeout.com/melbourne/news/why-is-the-yarra-river-so-brown-we-asked-an-expert-030824

Well, Chicago will have a green river on the 17th.

https://www.nbcchicago.com/news/local/when-the-chicago-river-will-be-dyed-green-for-st-patricks-day-and-how-its-done/3347247/

https://www.enjoyillinois.com/travel-illinois/the-history-of-chicago-river-dyeing