Detail this asset from Unity Store: Original Link
This is a paid asset, but now you can download Realistic Waterfall Free.
Realistic Waterfall v1.2
A realistic waterfall particle system. The effect is achieved with a combination of texture animations, mist particles, splash particles and UV scrolling.
Sound effects are also supplied.
New to version 1.1:
Waterfall can now be scaled to fit your scene.
Falling water now 3D (billboards no longer just face the camera).