Those two links show great quilts on the theme.
I designed and made one with two colors, but graded on the color theme using mainly fabrics from my stash. Mine was called "Sunshine on Water" but could be adjusted to create a river effect rather than a section of stream which I had visualized. You are welcome to use the idea.
I realize this looks "jittery" in the picture, but it isn't....that's a factor of the grading from one value to the next in color and, to me, adds to the water effect. Up close, in real life, of course, one does not see that dizzying effect!!
Jan in VA