.....can be a primary controversy ,before to imagine a gravity motor.
This topic is another formal saying of some older themes,as "Wheel vs. lever"...
Energy dissipation,below a hydraulic structure is accomplished generally by a single-fall hydraulic jump.
For a gravity motor,a single-fall jump,can be figured with the help of a lever concept...
So,a single-jump down,seems more favorable,to "sparkle" more kinetic energy between two gravitational levels (elevation) and .....to proof the validity of a gravity motor possibility?!
All the best! / Alex