Hydraulic Grade Line
Water
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. In open channels, the hydraulic grade line is equal to the water surface.
- — Service Hydrologist Reference Manual Glossary of Hydrologic Terms retrieved 2014-06-01
Weather
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.