Realistic Rapids is a Vintage Story mod by theblondie. Realistic Rapids changes waterwheel mechanics so waterfall height and steep drops, rather than special rapid water, determine flow speed.
Why this mod is worth installing
This addon is useful for players who want more believable water-powered machinery and enjoy designing terrain or channels around real vertical drops.
What Realistic Rapids adds
Realistic Rapids removes the need to search for a special rapid-water block to drive a waterwheel. The important factor becomes the height of the waterfall: a sufficiently high drop accelerates the water below it.
Water also keeps its increased speed while running down slopes that are steep enough. This makes the lower section beneath a waterfall the practical place to install a waterwheel.
The addon is designed for use with Realistic Water. It can be added to an existing world, but areas that have already been explored may need the water to dry out and flow again before the new behavior appears.
To check a planned site, watch the lower part of the cascade. Faster flow there indicates that the vertical drop is high enough for a waterwheel.
Where to download Realistic Rapids
The official Vintage Story Mod DB page is the right place to get the current release through the in-game mod manager.