What does the term "hydraulic grade line" refer to in water distribution?

The term "hydraulic grade line" refers to the elevation of water in a hydraulic system at any given point. It is an important concept in water distribution, representing the potential energy available to the water, which is dictated by its elevation and pressure. Specifically, the hydraulic grade line is calculated by adding the elevation head (the height of the water above a reference point) to the pressure head (which is the height of water that can be supported by the pressure at that point, expressed in feet or meters of water).

This line helps engineers and operators to visualize how water pressure varies throughout a distribution system and to design systems that maintain adequate pressure and flow. When considering the other options, the line indicating water pressure, the level of pollutants, and the maximum water storage level are related to different aspects of water management but do not represent the specific definition of the hydraulic grade line as it pertains to elevation in the context of hydraulic systems.