That's a very pretty map! Excellent job on the colours/textures, and I really like your style. Those hills in particular look really fantastic!

But yes, the rivers don't look right and don't match the style of the rest of the map.

The inner texture of the water looks good, but the white (almost glowing edge) doesn't look right, and makes them look like they're pasted on top of the terrain instead of recessed into the ground. What you might try is to actually cut them out of the base map (after saving the original, of course!) and then adding a very small black drop shadow on another layer. That way you can lower the opacity if need be, in case it's too dark. And your water texture would go underneath the drop shadow on it's own layer.

Also, one thing that really jumps out at me as looking wrong is that they're all too consistent with width. Try making them much more irregular in shape/width, for a more natural look. And they also don't seem to follow the lay of the land either. Maybe try drawing them with more switchbacks, as though following the angles on an isometric map.

I have no experience at all with rivers on this type of map, so I'm sure others will probably have much better advice for you, but that's just a few things I can suggest, from observing how others have done their rivers.