Another thing to watch out for is the termination points of the rivers because in the demo above the sides of the river and the mouths are correct but the end going towards land isn't and will be glitched (though usually you can dig around the outside with your waterscaping tools and either fill it in or dig it out to unglitch it). My acres aren't the best but hopefully you can also import them (into an instance of the save editor, without saving) and preview how to make a termination point for the top right river mouth if you get stuck. Another thing you can do is dig up your own body of water and either join it or copy the curvature of the water tiles to terminate a river or join it into an existing river.
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Thanks for the acre file! I figured that out for the most part, my only issue is I can't see how it looks in game because I can't save due to the NHSE crash. Does yours crash when you modify acres? I'm using NHSE version #20200413.3