Irrigation Glossary

Hard hose traveler

Large rotating sprinkler(s) mounted on a trailer to deliver water in a circle. The sprinkler and associated trailer are towed through the field by any of several means.
Travelers are also called cable-tow, hard hose and hose drag.

Head

atmospheric pressure Value of atmospheric pressure at a specific location and condition.
head, dynamic Specific energy in a flow system.
head, discharge Pressure head at the outlet of the pump.
head, elevation Head as a result of elevation above a defined datum.
head, friction Energy head loss caused by the friction of water flowing through a pipe.
head loss Energy loss in fluid flow.
head loss, converging and diverging pipes Energy loss associated with water flowing through converging or diverging pipe sections.
head loss, entrance Energy loss associated with water flowing through the entrance of a pipe.
head loss, bends Energy loss associated with water flowing through a bend in a pipe.
head, pressure Pressure energy in a liquid system expresses as the equivalent height of a water column above a given datum.
head, static Energy associated with a static liquid system composed of elevation and pressure components.
head, static discharge Static energy components at the discharge of a pump including elevation and pressure.
head, static suction Vertical distance from the pump centerline to the surface of the liquid when the liquid supply is above the pump.
head, total (dynamic )
- Head required to pump water from its source to the point of discharge. Equal to the static lift plus friction head losses in pipes and fittings plus velocity head.
- Energy in the liquid system expressed as the equivalent height of a water column above a given datum.
- Sum of static, pressure, friction and velocity head that a pump works against while pumping at a specific flow rate. (Reference Manual)
head, total suction Head required to lift water from the water source to the centerline of the pump plus velocity head, entrance losses and friction losses in suction pipeline.
head, vapor pressure Pressure head at which the liquid (water) will vaporize or boil at a given temperature.
head, velocity
- Head or energy caused by the velocity of a moving fluid.
- Amount of pressure required to generate a specific velocity. This is the amount of energy or pressure that is used to make the water move at a given velocity.

Head ditch Ditch across the upper end of a field used for distributing water in surface irrigation.

Head gate Water control structure at the entrance to a conduit or canal.

Head spacing: See spacing between sprinklers.

Head to head spacing Spacing of sprinkler heads so that each sprinkler throws water to the adjacent sprinkler.

Height (above a datum) Linear dimension used to describe the vertical distance from a point to a datum.

Herbicide Chemical substance designed to kill or inhibit the growth of plants, especially weeds.

High density polyethylene [HDPE] One of several forms of polyethylene used to make pipe and other irrigation components.

Horizon (soil) Layer of soil or soil material approximately parallel to the land surface and differing from adjacent genetically related layers in physical, chemical, and biological properties or characteristics such as color, structure, texture, consistency, kinds and number of organisms present, degree of acidity or alkalinity, etc.

Horsepower

water horsepower Energy added to water by a pump.
input horsepower Energy added to a motor or engine
brake horsepower Power required to drive a pump.

Hose bib Valve configured to be mounted on a wall having threads to accommodate the connection of a water hose.

Hose drag traveler

Large rotating sprinkler(s) mounted on a trailer to deliver water in a circle. The sprinkler and associated trailer are towed through the field by any of several means.
Travelers are also called cable-tow, hard hose and hose drag.

Humid climate Climate characterized by high rainfall and low evaporation potential. A region generally is considered as humid when precipitation averages more than 40 inches per year.

Hydrant Outlet, usually portable, used for connecting surface irrigation pipe to an alfalfa valve outlet.

Hydraulic conductivity

Coefficient describing the ease at which the soil pores permit water movement.
Soil-water characteristic describing the ability of water to flow through a particular soil.

Hydraulic valve Irrigation zone valve which uses small flexible tubes and water under pressure to provide the actuation signal from the controller to the valve.

Hydrozone Grouping of plants with similar water requirements so that they can be irrigated with a common zone.

Hygroscopic water

Water which is bound tightly by the soil solids at potential values lower than -31 bars.
Water that is tightly held by soil particles. It does not move with the influence of capillary action or gravity, and it is normally unavailable to plants.