Glossary of Irrigation Terms

A measure of the pressure at which an irrigation system actually operates. Calculated by taking the static pressure of the water at the point of connection to the water source and subtracting any pressure losses occurring through the system. The operating pressure is usually measured at the base or nozzle of the sprinklers.

An outlet valve fitted to the interior of a vertical pipe (sometimes known as a riser). The orchard valve features an opening the same size as the diameter of the pipe and an adjustable cover to enable the flow of water through the pipe to be varied. Orchard valves are similar to alfalfa valves, but deliver lower flow capacity.

Pressure, sometimes called potential, is a measure of the pressure caused by water as it moves through an irrigation system. Osmotic pressure is specifically the pressure of water which contains dissolved molecules, generally salts and other nutrients. Often the water will be passing through a semi-permeable membrane, from a less to a more concentrated solution of nutrients.