Looking at the map that you used as a reference (it must be Cyrus Harris’ map of Kentucky) makes me think that maybe, tracing the rivers, you could use thinner brushes for smaller streams, or maybe for all the rivers, you could use a dark grey colour instead of black or maybe you could use a subtle grey texture to fill the rivers; as it is, the rivers are too "black" and seem more lines drawn with a marker than rivers; and that could be the reason way some of the rivers seem “interlaced” while they’re not in the reference map. I even think that, being the reference map way much lighter (as for the background colour, an ivory off-white) than your map, it absorbs much more easily the contrast with the grey of the many rivers and tributaries. Maybe, as your map is already quite dark for your artistic needs, you could remove at least some of the tributaries, so that the map become less saturated with dark, obtruding elements.