Standpipe level; piezometric head
The energy of the stationary water, this means the potential energy is the mechanical energy that has a body of water relative to a known reference level due to its location.
The potential energy level or the hydraulic potential describe the waters state of energy in the soil at a point defined by the measurement. In the case of the ground water, the hydraulic potential is also called the vertical or piezometric level height. In the case of hydropower plants it refers to the hydraulic fall heigh.
Translated from "DIN 4044"; translated from wikipedia.org
https://de.wikipedia.org/wiki/Hydraulisches_Potential (retrieved 24.08.2017)