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Irrigation Glossary


gate, slide gate: Device used to control the flow of water to, from, or in a pipeline or open channel ...  (NRCS, 1997)
gated pipe: Portable pipe with small gates installed along one side for distributing irrigation water to corrugations or furrows. (ASAE, 1998)
gear drive sprinkler: See sprinkler head.
gpm* {gpm, m3/s}: Acronym for gallons per minute. See flow rate.
gravitational water: Soil water that moves into, through, or out of the soil under the influence of gravity. (NRCS, 1997)
gravity (acceleration due to)* [g] {ft/s2, m/s2} (11/6/99)Acceleration caused by the attraction of the mass of earth to bodies at or near its surface. (i.e. 32.2 ft/sec2)
gray water: Domestic wastewater other than that containing human excreta such as sink drainage, washing machine discharge, or bath water. (ASAE, 1998)
gross irrigation: See irrigation, gross.
gross irrigation system capacity: See system capacity, gross irrigation
gross water (irrigation) requirement: See irrigation requirement, gross.
ground water: Water occurring in the zone of saturation in an aquifer or soil. (NRCS, 1997)
growing season {days}: Period, often the frost-free period, during which the climate is such that crops can be produced. (NRCS, 1997)
gypsum block: Electrical resistance block in which the material used to absorb water is gypsum. It is used to measure soil water content in non-saline soils. (NRCS, 1997)
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hard hose traveler: See irrigation system: traveler.
head [H] {ft, m}: atmospheric pressure *(head) [Ha] (11/6/99) Value of atmospheric pressure at a specific location and condition.

  • head, dynamic {ft, m}: Specific energy in a flow system. (ASAE, 1998) 
  • head, discharge [Hd]: Pressure head at the outlet of the pump. (Pumps, 1998) 
  • head, elevation* [Hz, Z] (11/6/99): Head as a result of elevation above a defined datum. 
  • head, friction*[Hf] (11/6/99): Energy head loss caused by the friction of water flowing through a pipe. 
  • head loss*[HL] (11/6/99): Energy loss in fluid flow. (ASAE, 1998) head loss, converging and diverging pipes [Hg] {ft, m} (approved via RM) Energy loss associated with water flowing through converging or diverging pipe sections. (Reference Manual, ch. 2) 
  • head loss, entrance [He] {ft. m} (approved via RM): Energy loss associated with water flowing through the entrance of a pipe. (Reference Manual, ch. 2) 
  • head loss, bends [Hb] {ft, m} (approved via RM): Energy loss associated with water flowing through a bend in a pipe. (Reference Manual, ch. 2) 
  • head, pressure* [Hpr] (11/6/99): Pressure energy in a liquid system expresses as the equivalent height of a water column above a given datum. (ASAE, 1998) 
  • head, static* [Hs]  (11/6/99): 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.  (Pumps, 1998) 
  • head, total (dynamic )* [Ht, H, TDH] (11/6/99)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. (NRCS, 1997). Energy in the liquid system expressed as the equivalent height of a water column above a given datum. (ASAE, 1998). 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. (ASAE, 1998)  
  • head, vapor pressure* [Hvp]  (11/6/99): Pressure head at which the liquid (water) will vaporize or boil at a given temperature. 
  • head, velocity* [Hv] (11/6/99): Head or energy caused by the velocity of a moving fluid...  (ASAE, 1998). 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. (Monroe, 1995)

head ditch: Ditch across the upper end of a field used for distributing water in surface irrigation. (ASAE, 1998)
head gate: Water control structure at the entrance to a conduit or canal. (ASAE, 1998)
head loss: See head.
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) [z] {ft, m}: 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. (NRCS, 1997)
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. (Soil, 1996)
horsepower {hp, kw}:

  • water horsepower* [Whp, WHP] (11/6/99): Energy added to water by a pump. (Reference Manual) 
  • input horsepower* [Ihp, IHP]:  Energy added to a motor or engine 
  • brake horsepower* [Bhp, BHP]  (11/6/99): Power required to drive a pump. (Reference Manual) 
  • miscellaneous component energy losses [HPx] {hp} (Reference Manual, ch. 4)

hose bib: Valve configured to be mounted on a wall having threads to accommodate the connection of a water hose.
hose drag traveler: See irrigation system.
humid climate: See climate.
hydrant: Outlet, usually portable, used for connecting surface irrigation pipe to an alfalfa valve outlet. (NRCS, 1997)
hydraulic conductivity* [K] {in./h, mm/h}:

  • Coefficient describing the ease at which the soil pores permit water movement. (NRCS, 1990) 
  • Soil-water characteristic describing the ability of water to flow through a particular soil.

hydraulic valve: See valve.
hydrozone: Grouping of plants with similar water requirements so that they can be irrigated with a common zone. (Weinberg and Roberts, 1988)
hygroscopic water: 

  • Water which is bound tightly by the soil solids at potential values lower than -31 bars. (NRCS, 1990)
  • 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. (Drip, 1999.)

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ID* {in., mm} (11/6/99)Abbreviation for inside diameter (usually of a pipe).
impact drive: See sprinkler head.
impact drive sprinkler: See sprinkler head.
impact power {watts, horsepower}:

  • Rate at which drops deliver kinetic energy to the soil. (Solomon, et al. 1996)
  • Kinetic energy of impact on soil per unit volume. (Contractor pg 36, 1999)

impact rate {hp/ft2, kw/m2}:

  • Impact power per unit area. (Solomon, et al, 1996) 
  • Impact power per square foot. (Contractor pg 36, 1999)


  • See also intake rate.
  • Process of water movement through the soil surface into the soil matrix. (Burt et al, 1997). 
  • The act of water entering the soil profile. (Rain Bird, 1997)

infiltration rate [I] {in./h, in.3/h/in.2, mm/h} (Preferred term is intake rate.):

  • Downward flow of water into the soil at the air-soil interface.  (NRCS, 1997) 
  • Volume of water infiltrating through a horizontal unit area of soil surface at any instant. (Hess, 1999) 
  • How quickly water moves into the soil. (Monroe, 1993)

infiltrometer: Device used to measure the infiltration rate / intake rate of water into soil. (NRCS, 1997)
ring infiltrometer: Consists of metal rings that are inserted (driven) into the soil surface and filled with water. The rate at which water enters the soil is observed. (NRCS, 1997)
sprinkler infiltrometer: Consists of a sprinkler head(s) that applies water to the soil surface at a range of rates of less-than to greater than soil infiltration rates. Maximum infiltration rates are observed and recorded. (NRCS, 1997)
flowing infiltrometer: Consists of an inlet device to apply a specific flow rate to a furrow and a collection sump with a pump to return tail water to the inlet device. Water infiltrated by the soil in the test section (typically 10 meters) is replaced with water from a reservoir to keep the flow rate constant. The rate of water infiltrated verses time is also plotted. An equation (typically for a curvilinear line) then represents the intake characteristics for that particular soil condition. (NRCS, 1997)
initial intake: See intake.
input horsepower: See horsepower.
inrush current {amps}: Current necessary to initially open the solenoid valve. (Smith, 1997)
instantaneous application rate: See precipitation rate.
intake family: Grouping of intake characteristics into families based on field infiltrometer tests on many soils.   (NRCS, 1997)
intake, initial {in./h, mm/h}: Depth (rate) of water absorbed by a soil during the period of rapid or comparatively rapid intake following initial application. (NRCS, 1997)
intake rate (of soil)* [ I] {in./h, mm/h }: Rate that (irrigation) water enters the soil at the surface. (NRCS, 1997)
intake rate (basic)* [Ib] {in./h, mm/h}: Rate at which water percolates into the soil after infiltration has decreased to a low and nearly constant value. (ASAE, 1998)
interception {in., mm}: Part of precipitation or sprinkler irrigation system applied water caught on the vegetation and prevented from reaching the soil surface. (NRCS, 1997)
internal manual bleed: Feature which allows an automatic valve to be opened manually (without controller) by releasing water from above the diaphragm to the downstream side of the valve. Useful during installation, system start-up and maintenance operations when it is undesirable for water to escape into the valve box. (Rain Bird, 1997)
inverted siphon: Closed conduit (for conveying water) with end sections above the middle section; used for crossing under a depression, under a highway or other obstruction. Sometimes called a sag pipe. (NRCS, 1997)
IPS: See iron pipe size.
iron pipe size* [IPS] {in., mm}: One of several systems which specify pipe dimensions.
irrecoverable water loss {in., mm}: Water loss that becomes unavailable for reuse through evaporation, phreatophytic transpiration, or ground-water recharge that is not economically recoverable. (NRCS, 1997)
irrigable area {acres, ha}: Area capable of being irrigated, principally based on availability of water, suitable soils, and topography of land. (NRCS, 1997)

  • Intentional application of water to the soil, usually for the purpose of crop production (reclaiming soils, temperature modification, improving crop quality). (Soil, 1996) 
  • Intentional application of water for purposes of sustained plant growth and/or optimized production. (Spofford, T. L., 1999. Unpublished)


  • gross [Igross] {in., mm}: Water actually applied, which may or may not be total irrigation water requirement; i.e. leaving storage in the soil for anticipated rainfall, harvest. (NRCS, 1997) 
  • net [Inet] {in., mm}: Actual amount of applied irrigation water stored in the soil for plant use or moved through the soil for leaching salts. Also includes water applied for crop quality and temperature modification; i.e. frost control, cooling plant foliage and fruit. Application losses, such as evaporation, runoff, and deep percolation, are not included. (NRCS, 1997) See also, irrigation requirement, net.

irrigation audit: Procedure to collect and present information concerning the uniformity of application, precipitation rate, and general condition of an irrigation system and its components. (Carruthers, B. 2001, unpublished)
irrigation consumptive use coefficient [ICUC] {-}: See coefficient.
irrigation design: Plan of an irrigation system with pipe sizing, head layout and valve location.  (Masdon, S.,  Water Management Committee, 2001)
irrigation district: Cooperative, self-governing, semipublic organization set up as a subdivision of a state or local government to provide irrigation water. (NRCS, 1997)
irrigation efficiency: See efficiency.
irrigation frequency* {-/week}: Measure of the number of irrigations per unit time.
irrigation interval* [IN] {h, days} (approved via RM): Average time interval between the commencement of successive irrigations for a given field (or area). (ASAE, 1998) 
Time between irrigation events. Usually considered the maximum allowable time between irrigations during the peak ET period. (NRCS, 1997)
irrigation period* {h}: Time that it takes to apply one irrigation to a given design area during the peak consumptive-use period of the crop being irrigated. (Soil, 1996)
irrigation (water) requirement:

  • net irrigation requirement* [IRnet, ] {in., mm} (11/6/99)Depth of water, exclusive of effective precipitation, stored soil moisture, or ground water, that is required for meeting crop evapotranspiration for crop production and other related uses. Such uses may include water required for leaching, frost protection, cooling and chemigation. (NRCS, 1997). Difference between  evapotranspiration and effective precipitation. (Landscape, 1996). Quantity of water needed by the landscape to satisfy the evaporation, transpiration and other uses of the water in the soil. (Rain Bird, 1997) 
  • gross irrigation requirement*[IRgross,  ] {in., mm} (11/6/99):  Total amount of water applied (or desired). See also irrigation water requirement. Total irrigation requirement including net crop requirement plus any losses  incurred in distributing and applying and in operating the system. (NRCS, 1997) 
  • irrigation water requirement [IWR] {in., mm}: Calculated amount of water needed to replace soil water used by the crop (soil water deficit), for leaching undesirable elements through and below the plant root zone, plus other needs; after considerations are made for effective precipitation. (NRCS, 1997). Plant water requirement adjusted for application uniformity (and efficiency). (Contractor, 1999) (Same as gross irrigation requirement.)

irrigation sagacity [IS] {%}: Ratio of volume of irrigation water beneficially or reasonably used to the total volume of irrigation water that has left the region, both in a specified period of time. (Burt et al, 1997)
irrigation schedule: 

  • Procedure of establishing and implementing the time and amount of irrigation water to apply. 
  • Determining when to irrigate and how much water to apply, based upon measurements or estimates of soil moisture or crop water used by a plant. (NRCS, 1997) 
  • Set of specifications identifying times to turn on and off water to various zones of an irrigation system.

irrigation scheduling: See scheduling.
irrigation set {acres, ha}: Area irrigated at one time within a field. (Soil, 1996)
irrigation set time: See set time.
irrigation slope {%, ft / 100 ft, m/100m}: Elevation difference along the direction of irrigation. Sometimes called irrigation grade. (NRCS, 1997)
irrigation system: Physical components (pumps, pipelines, valves, nozzles, ditches, gates, siphon tubes, turnout structures) and management used to apply irrigation water by an irrigation method.  (NRCS, 1997). All equipment required to convey water to or within the design area. (ANSI/ASAE S376.2 JAN98). Set of components which includes (may include) the water source, water distribution network, control components and possibly other general irrigation equipment. (Rain Bird, 1997) 

  • drip/trickle/micro: Micro irrigation system (low pressure and low volume) wherein water is applied to the soil surface as drops or small streams through emitters.  Preferred term is drip irrigation. (NRCS, 1997). Method of micro-irrigation wherein water is applied to the soil surface (or below the soil surface) as drops or small streams through emitters.  Discharge rates are generally less than 2 gph for single-outlet emitters and 3 gph per meter for line-source emitters. (ASAE, 1998). Method of micro irrigation wherein water is applied to the soil surface as drops or small streams through emitters (preferred term is drip irrigation). (ASAE, 1998) 
  • bubbler irrigation: Application of water to flood the soil surface using a small stream or fountain.  The discharge rates for point-source bubbler emitters are greater than for drip or subsurface emitters but generally less than 1 gpm.  A small basin is usually required to contain or control the water. (ASAE, 1998) 
  • surface: Type of irrigation where water is distributed to the plant material by a ground surface distribution network possibly including rows or dikes. Broad class of irrigation methods in which water is distributed over the soil surface by gravity flow. (ASAE, 1998) 
  • basin irrigation: Irrigation by flooding areas of level land surrounded by dikes. Used interchangeably with level border irrigation, but usually refers to smaller areas. (ASAE, 1998) 
  • border irrigation: Irrigation by flooding strips of land, rectangular in shape and cross leveled, bordered by dikes.  Water is applied at a rate sufficient to move it down the strip in a uniform sheet.  Border strips having no down field slope are referred to as level border systems.  Border systems constructed on terraced lands are commonly referred to as benched borders. (ASAE, 1998) 
  • cablegation: Method of surface irrigation that uses gated pipe to both transmit and distribute water to furrows or border strips.  A plug, moving at a controlled rate through the pipe, causes irrigation to progress along the field and causes flow rates from any one gate to decrease continuously from some maximum rate to zero. (ASAE, 1998) 
  • check irrigation: Modification of a border strip with small earth ridges or checks constructed at intervals  to retain water as the water flows down the strip. (ASAE, 1998) 
  • check basin irrigation: Water is applied rapidly to relatively level plots surrounded by levees. The basin is a small check. (Soil, 1996) 
  • corrugation irrigation:  Method of surface irrigation similar to furrow irrigation, in which small channels, called corrugations, are used to guide water across a field.  No attempt is made to confine the water entirely to the corrugations. (ASAE, 1998) 
  • flood irrigation: Method of irrigation where water is applied to the soil surface without flow controls, such as furrows, borders or corrugations. (ASAE, 1998) 
  • furrow irrigation: Method of surface irrigation where the water is supplied to small ditches or furrows for guiding across the field. (ASAE, 1998)
  • alternate set irrigation: Method of managing irrigation whereby, at every other irrigation, alternate furrows are irrigated, or sprinklers are placed midway between their locations during the previous irrigation. (ASAE, 1998) 
  • alternate side irrigation: Practice of furrow irrigating one side of a crop row (for row crops or orchards) and then, at about half the irrigation time, irrigating the other side. 
  • cutback irrigation: Reduction of the furrow or border inflow stream after water has advanced partially or completely through the field in order to reduce runoff. (ASAE, 1998) 
  • surge: Surface irrigation technique wherein flow is applied to furrows (or less commonly, borders) intermittently during a single irrigation set. (ASAE, 1998) 
  • wild flooding: Surface irrigation system where water is applied to the soil surface without flow controls, such as furrows, borders (including dikes), or corrugations. (NRCS, 1997) 
  • sprinkler: Type of irrigation using mechanical devices with nozzles (sprinklers) to distribute the water by converting water pressure to a high velocity discharge stream or streams.
  • continuous/self-move system: Lateral, sprinkler (traveler), or boom that is continuous or self moving while water is being applied.  Power for moving the facility is typically provide by electric or hydraulic (water) motors or small diesel engines.  (NRCS, 1997) 
  • boom: Elevated, cantilevered boom with sprinklers mounted on a central stand.  The sprinkler-nozzle trajectory back pressure rotates the boom about a central pivot which is towed across the field by a cable attached to a winch or tractor.  Can also be a periodic-move system. (NRCS, 1997) 
  • center pivot: Automated irrigation system consisting of a sprinkler lateral rotating about a pivot point and supported by a number of self-propelled towers.  Water is supplied at the pivot point and flows outward through the pipeline supplying the individual sprinklers or spray heads. (NRCS, 1997) 
  • corner pivot: Additional span or other equipment attached to the end of a center pivot irrigation system that allows the overall radius to increase or decrease in relation to field boundaries. (NRCS, 1997) 
  • lateral (linear) move: Automated irrigation machine consisting of a sprinkler line supported by a number of self-propelled towers.  The entire unit moves in a generally straight path perpendicular to the lateral and irrigates a basically rectangular area. (NRCS, 1997) (Soil, 1996) 
  • traveler (traveling gun) irrigation: 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. ... (NRCS, 1997). Travelers are also called cable-tow, hard hose and hose drag.  
  • periodic-move system: System of laterals, sprinklers heads (gun types), or booms that are moved between irrigation settings.  They remain stationary while applying water. (NRCS, 1997)
  • gun type: Single sprinkler head with large diameter nozzles, supported on skids or wheels.  Periodically moved by hand or mechanically with a tractor, cable, or water supple hose. ...  (NRCS, 1997) 
  • portable (hand move) irrigation: Sprinkler system which is moved by uncoupling and picking up the pipes manually, requiring no special tools. (Soil, 1996) 
  • side move: Sprinkler system with the supply pipe supported on carriages and towing small diameter trailing pipelines each fitted with several sprinkler heads. (NRCS, 1997) 
  • side role (wheel line): Supply pipe is usually mounted on wheels with the pipe as the axle and where the system is moved across the field by rotating the pipeline by engine power. (NRCS, 1997) 
  • towed sprinkler: System where lateral lines are mounted on wheels, sleds, or skids and are pulled or towed in a direction approximately parallel to the lateral.  Rollers or wheels are secured in the ground near the main water supply line to force an offset in the tow path equal to half the distance the lateral would have been moved by hand. (NRCS, 1997) 
  • solid set/fixed: System of portable surface or permanently buried laterals totally covering the irrigated area or field.  Typically several adjacent laterals or heads are operated at one time.  Portable laterals are typically removed from the field at end of germination, plant establishment, or the irrigation season and are replaced the next irrigation system. (NRCS, 1997)

irrigation water requirement: See irrigation requirement.
isolation valve: See valve.