Black lines tracing rivers

As I flew the Patagonia Bush Flight, I saw some, otherwise beautiful mountain rivers with black lines roughly tracing their paths. What is that? It almost looks like someone took a drying-out black marker and followed the river paths.

I was in VR and could not take a screen shot.

Is there water in the river? Water masks generally cover it.

These lines have been around since release. Lines around lakes and down the center of rivers.

https://forums.flightsimulator.com/search?q=Lines%20in%20river

Yes, the water is there too. The lines I see in lakes are straight, like they might be Microsoft satellite pass dividing lines. The river look like they are hand traced.

I went back (non-VR) to get a screen shot of an example.

Often times the autogen rivers gets in the way of nice-looking satellite imagery.

That can explain it. By the way, that Patagonia bush trip is beautiful.

Thank you for the screenshot. That is different than what I was thinking in which has been around since day 1.