You may find that your Varipump has a two pin plug - cutting the plug will not void your guarantee.
The plug can be cut off and wired into a safe, compliant, outdoor electrical system, with an RCD cut-off. If you are unsure, consult a qualified...
How do I calculate the head height?
To find the head height, measure the vertical distance from the surface of the water to the top of the waterfall. Remember to add 1 foot of head for every 10 feet of pipe that will connect the pump and waterfall.