For a river known as the “golden watercourse,” red is a strange color to see. Yet that’s the shade turning up in the Yangtze River and officials have no idea why. The red began appearing in the Yangtze, the longest and largest river in China…
via Yangtze River Turns Red and Turns Up a Mystery.
What are the possible reasons for this color change? What are scientists investigating as suspect sources? What do you think: Is this a physical or a chemical change?
We Need Fresh Air 
Chemical because of the color change. Pollution and negative human interaction with the river is the most probable cause, but an unknown accident, such as a spill from nearby factories, could also be the problem.
I think it is a chemical change because it is an UNEXPECTED color change. Maybe, there is an unknown substance that has been mixed with the water and reacted to result in a color change. Or, the river has been polluted by factories or individuals. Scientists also believe the source to be pollution.