Definitions for "Hydraulic Grade Line"
In hydrologic terms, a line whose plotted ordinate position represents the sum of pressure head plus elevation head for the various positions along a given fluid flow path, such as along a pipeline or a ground water streamline.
A hydraulic profile of the piezometric level of water at all points along a pipeline or open conduit. The term is usually applied to water moving in a conduit, open channel or stream, but may also be applied to free or confined groundwater. In an open channel, it is the free water surface.
In a closed channel, a line joining the elevations that water would attain in atmospheric pressure; in an open channel, the free water surface.