hydraulic head In general, the elevation of a water body above a particular datum level. Specifically, the energy possessed by a unit weight of water at any particular point, and measured by the level of water in a manometer at the laboratory scale, or by water level in a well, borehole, or piezometer in the field. The hydraulic head consists of three parts: the elevation head (see ELEVATION POTENTIAL ENERGY), defined with reference to a standard level or datum; the pressure head, defined with reference to atmospheric pressure; and the velocity head. Water invariably flows from points of larger hydraulic head to points of lower head, down the hydraulic gradient.

hydraulic head In general, the elevation of a water body above a particular datum level. Specifically, the energy possessed by a unit weight of water at any particular point, and measured by the level of water in a manometer at the laboratory scale, or by water level in a well, borehole, or piezometer in the field. The hydraulic head consists of three parts: the elevation head (see elevation potential energy), defined with reference to a standard level or datum; the pressure head, defined with reference to atmospheric pressure; and the velocity head. Water invariably flows from points of larger hydraulic head to points of lower head down the hydraulic gradient.