I'd be interested in rivers, too, but so far this mod seems only to paint a type of blue terrain tile in elongated shapes; they're not water, and the player can walk (wade?) down the "river" at the same speed s/he can walk on the "land".
The mod I'd like to see would connect lakes with water, and provide a bridge landfill type. Then it would have mobile entities like rafts, canoes and stern-wheel paddle steamers... Too much, I know!
https://www.dropbox.com/s/bc4pd0978x6pnky/Screenshot_20180324_171739.png?dl=0