Hydro-electricity is fundamentally the combination of water flow and vertical drop (commonly called “head”). Vertical drop creates pressure, and the continuous flow of water in a hydro system gives us an ongoing source of pressurized liquid energy. Pressurized, flowing water is a very dense resource, and hydro-electric systems convert a very large percentage of the available energy into electricity because the resource is captive in a pipe or flume.
Direct Height Measurement
To measure head, you can use a laser level, a surveyor’s transit, a contractor’s level on a tripod, or a sight level (“peashooter”). Direct measurement requires an assistant.
One method is to work downhill using a tall pole with graduated measurements. A measuring tape affixed to a 20-foot (6 m) section of PVC pipe works well. After each measurement, move the transit, or person with the sight level, to where the pole was, and begin again by moving the pole further downhill toward the generator site. Keep each transit or sight level setup exactly level, and make sure that the measuring pole is vertical. Take detailed notes of each measurement and the height of the level. Then, add up the series of measurements and subtract all of the level heights to find total head.
Another method is to work uphill, with your assistant walking up the slope as you site through the transit or sight level until the bottoms of the assistant’s feet are level with the transit. At this point, the head will be the same as the distance from your eye to the ground where you are standing. Once you’ve recorded this measurement, move to the spot where your assistant was standing, and repeat the process. Multiply the number of times you do this by the height of the shooter’s eye from the ground for the total head.