is the height of a column of fluid that will produce a given pressure: h =: p/w where h is the height of the column of fluid p is the pressure generated by the head w is the specific weight of the fluid A column of water 28" high will produce a pressure of 1 PSI.
Pressure in head units, for example, meters of fluid, equal to the force per unit area divided by the product of the density of the fluid and the acceleration due to gravity. It is the depth of fluid that would exert an equivalent pressure.
The pressure energy necessary at the distribution water system entrance to overcome losses and operate various irrigation equipment/emitters at the designed pressure.