The pressure caused by the weight of an equivalent column of liquid upon a unit area expressed by the height or distance of the liquid above the point at which the pressure is measured. Although head refers to distance or height, it is used to express the pressure resulting from the weight of a body of liquid since the weight is directly proportional to the height.

The pressure exerted by a fluid at a given depth beneath a surface. It is proportional to the height of the fluid's surface above the area where the pressure is measured.

the force exerted by a column of liquid expressed by the height of the liquid above the point at which the pressure is measured. Although "head" refers to distance or height, it is used to express pressure, since the force of the liquid column is directly proportional to its height. Also called head or hydrostatic head. Compare hydrostatic pressure.

'Hydraulic head' is simply the level to which groundwater would rise within an open standpipe (or 'piezometer') inserted into the saturated zone, and is a measure of the pressure that the water is under at that location

In hydrologic terms, (1) The height of the free surface of a body of water above a given point beneath the surface. (2) The height of the water level at the headworks, or an upstream point, of a waterway, and the water surface at a given point downstream. (3) The height of a hydraulic grade line above the center line of a pressure pipe, at a given point.

Hydraulic Head - Water-level elevation in a well, or elevation to which the water of a flowing artesian well will rise in a pipe extended high enough stop the flow.

Difference in height between a point and the free water surface above or below.

(a) The height of the free surface of a body of water above a given subsurface point. (b) The water level at a point upstream from a given point downstream.

(head) the energy that causes groundwater to flow; the total mechanical energy per unit weight; the sum of the elevation head and the pressure head

In hydrologic terms, the height that water in an aquifer can raise itself above an (arbitrary) reference level (or datum) and is generally measured in feet. This term defines how much energy water possesses. When a borehole is drilled into an aquifer, the level at which the water stands in the borehole (measured with reference to a horizontal datum such as sea level) is, for most purposes, the hydraulic head of water in the aquifer.

The vertical distance between the surface of the reservoir and the surface of the river immediately downstream from the dam.

Head is the energy of a body of water produced by elevation, at a given pressure and temperature. It is a measure of potential energy of a body of water.

The elevation that water rises to in a well open to a specific point in the subsurface. Consists of two components: 1) pressure head, and 2) elevation head.

Difference in water height between upstream and downstream sides of a structure

The distance between the respective elevations of the upstream water surface (headwater) above and the downstream surface water (tailwater) below a hydroelectric power plant.

The sum of the elevation head and the pressure head. Same as piezometric head.

Hydraulic head is a specific measurement of water pressure or total energy per unit weight above a datum. It is usually measured as a water surface elevation, expressed in units of length, but represents the energy at the entrance (or bottom) of a piezometer. In an aquifer, it can be calculated from the depth to water in a piezometric well (a specialized water well), and given information of the piezometer's elevation and screen depth.