Q: I live in Cumming and have a small stream in the woods behind my house. The water looks like rust. Can you tell me why?

A: It’s because iron has dissolved in the water and a certain bacteria is feeding on it. The phenomenon is common in spring when the water warms and there is plenty of runoff from red clay. The same conditions cause the oily sheen you’ll sometimes see in stream pools. Generally speaking, it’s considered normal and the rusty water will disappear on its own.

see Iron Deposits in Water