Zooming in, I find it interesting that you have dark streaks, then there is a place where it seems that there is regular flooding, and a large dark area on the land where that sediment goes, and then the river turns much whiter.

Some of the white stuff also leaves the river there.

See [link|http://maps.google.com/maps?ll=31.552230,-114.959800&spn=0.008186,0.012048&t=k&hl=en|http://maps.google.c....012048&t=k&hl=en] for an example.

Cheers,
Ben