Thanks to Guzio for smoothing the tall waterfall mesh. Added an optional Waterfalls and Effects Add-On. Improved river flow, adjusted things a bit so that the most shallow streams (like the one near Whiterun) don't seem completely transparent. Added installer, 2K textures for better performance and an alternative version with wavy river waters. Also please do not use my assets for any purposes of your own. Please do not ask for compatibility patches since I doubt I have time to create any. Bug reports and that sort of things are more than welcome, though. If you have any bright ideas on how you would personally prefer the water to look that's all great but please keep it to yourself, I'm not interested. But like always, it's best to simply play with the parameters to find out a good balance for the given preset and weather modification you're using. In general, I've found that for best visual results, you should use higher AmbientIntensity and lower LightingIntensity during daytime and vice versa for night-time (higher LightingIntensity and lower AmbientIntensity). When using the Waterfalls and Effects Add-On, do keep in mind that you can adjust the brightness of waterfalls and related effects with LightingIntensity and AmbientIntensity parameters under section.
This should improve the quality of the game's build-in screen space reflections with the expense of minor performance hit: