What do you call that thing, you know, that whatchama call it with the dohickey on the end? Welcome to Irrigation Terms 101, where you'll learn the name of the whatchama call it, and what that dohickey on the end is called. The irrigation terms herein are used with permission from the Irrigation Association (www.irrigation.org/glossary-terms.htm), edited by Eugene Rochester, CID, certification consultant.
The terms have not been approved by the IA, or the IA Certification Board. The Irrigation Association (IA) is a nonprofit organization dedicated to improving the products and practices used to manage water resources and to help shape the irrigation industry. The IA's interest in water resources encompasses conservation, drainage, improvement and recovery of water for economic and environmental enhancement in agriculture, turfgrass, landscape and forestry.
AC pipe: Asbestos-cement pipe was commonly used for buried pipelines. It combines strength with light weight and is immune to rust and corrosion. (No longer made.)
adjusted sodium adsorption ratio: Index of permeability problems, based upon water quality.
advance ratio: Ratio of the time for the water to reach the end of the field to the total set time for an irrigation set on a furrow irrigation system. The ratio should be less than 0.5 to have a good distribution uniformity.
aeration capacity: Volume fraction of air filled pores in a soil at field capacity.
alfalfa valve: Outlet valve attached to the top of a pipeline riser with an opening equal in diameter to the inside diameter of the riser pipe and an adjustable lid or cover to control water flow.
anion: Negatively charged ion, which during electrolysis is attracted toward the anode. The most common anions in soil extracts and waters are bicarbonate, sulphate, carbonate, chloride and nitrate ions.
atmospheric vacuum breaker: Backflow device configured with a single moving part, a float, which moves up or down to allow atmospheric air into the piping system. The AVB is always placed downstream from all shut-off valves. Its air inlet valve closes when the water flows in the normal direction. But, as water ceases to flow the air inlet valve opens, thus interrupting the possible backsiphonage effect. This type of assembly must always be installed at least six inches above all downstream piping and outlets. Additionally, this assembly may not have shut-off valves or obstructions downstream. A shut-off valve would keep the assembly under pressure and allow the air inlet valve (or float check) to seal against the air inlet port, thus causing the assembly to act as an elbow, not a backflow preventer. The AVB may not be under continuous pressure for this same reason. An AVB must not be used for more than 12 out of any 24-hour period. It may be used to protect against either a pollutant or a contaminant, but may only be used to protect against a backsiphonage condition.
Blaney-Criddle Method: Air temperature based method to estimate crop evapotranspiration.
border dike: Earth ridge or small levee built to guide or hold irrigation or recharge water in a field.
British thermal units: Amount of heat required to raise the temperature of one pound of water from 63 to 64 degrees Fahrenheit.
capillary water: Water held in the capillary, or small pores of the soil, usually with soil water pressure (tension) greater than 1/3 bar. Capillary water can move in any direction.
cation: Positively charged ion which during electrolysis is attracted towards the cathode. Sodium, potassium, calcium and magnesium are the most common cations in waters and soil extracts.
cation exchange capacity: The measure of the positively charged ions in a soil matrix. The sum of exchangeable cations (usually Ca, Ma, K, Na, Al, H) that the soil constituent or other material can adsorb at a specific pH, usually expressed in centimoles of charge per Kg of exchanger (cmol/Kg), or milli equivalents per 100 grams of soil at neutrality (pH = 7.0), meq/100g.
Certified Irrigation Contractor (CIC): The Certified Irrigation Contractor is an irrigation professional whose principle business is the execution of contracts and subcontracts to install, repair and maintain irrigation systems. The CIC must conduct business in such a manner that projects meet the specifications and requirements of the contract.
Certified Irrigation Designer (CID): The IA Certified Irrigation Designer engages in the preparation of professional irrigation designs. They evaluate site conditions and determine net irrigation requirements based on the needs of the project. The designer is then responsible for the selection of the most effective irrigation equipment and design methods. The objective of a CID is to establish specifications and design drawings for the construction of an irrigation project.
Certified Landscape Irrigation Auditor (CLIA): The Certified Landscape Irrigation Auditor is involved in the analysis of landscape irrigation water use. Auditors collect site data, make maintenance recommendations and perform water audits. Through their analytical work at the site, these irrigation professionals develop monthly irrigation base schedules. Prior to certification examination, auditors are required to take an Irrigation Association approved preparatory course.
Certified Landscape Irrigation Manager (CLIM): The Certified Landscape Manager is an irrigation professional familiar with all areas of turf irrigation design and construction management. CLIMs must be certified as CICs, CIDs (all specialty areas), and CLIAs. Certified Landscape Irrigation Managers have extensive experience in design, construction, construction management and auditing of turf irrigation systems.
chemigation: Application of chemicals (including fertilizers) to crops through an irrigation system by mixing them with the irrigation water.
class (pipe): Term generally used to describe the pressure rating of SDR-PR (standard dimension ratio-pressure rated) PVC pipe, e.g., class 200 pipe has a pressure rating of 200 psi. Term used to identify the physical characteristics of thermoplastic pipe.
dielectric union: Pipe connection (union) having an insulator between the two sides of the union for the purpose of reducing corrosion caused by galvanic action.
emission uniformity: Index of the uniformity of emitter discharge rates throughout a micro-irrigation system. Takes account of both variations in emitters and variations in the pressure under which the emitters operate.
emitter (continuous flushing): Micro irrigation system emitter designed to continuously permit passage of large solid particles while operating at a trickle or drip flow, thus reducing filtration requirements.
evapotranspiration: Combination of water transpired from vegetation and evaporated from the soil and plant surfaces.
evaporation pan: Standard U.S. Weather Bureau Class-A pan (48-inch diameter by 10-inch deep) used to estimate the reference crop evapotranspiration rate.
friable: The ease with which the soil aggregates may be crumbled (in the hand).
friction factor, Christiansen: Coefficient used in the Christiansen Procedure to determine pressure loss in a multiple outlet piping system.
furrow dike: Small earth dike formed in a furrow to prevent water translocation. Typically used with LEPA and LPIC systems. Also used in non-irrigated fields to capture and infiltrate precipitation. Sometimes called reservoir tillage.
high density polyethylene: One of several forms of polyethylene used to make pipe and other irrigation components.
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.
basin irrigation: Irrigation by flooding areas of level land surrounded by dikes. Used interchangeably with level border irrigation, but usually refers to smaller areas.
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.
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.
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.
check basin irrigation: Water is applied rapidly to relatively level plots surrounded by levees. The basin is a small check.
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.
leaching requirement: Quantity of irrigation water required for transporting salts through the soil profile to maintain a favorable salt balance in the root zone for plant development.
Low Energy Precision Application [LEPA]: A water, soil, and plant management regime where precision down-in-crop applications of water are made on the soil surface at the point of use. Application devices are located in the crop canopy on drop tubes mounted on low pressure center pivot and linear move sprinkler irrigation systems.
Low Pressure In Canopy [LPIC]: Low-pressure in-canopy system that may or may not include a complete water, soil and plant management regime as required in LEPA. Application devices are located in the crop canopy with drop tubes mounted on low-pressure center pivot and linear move sprinkler irrigation systems.
manufacturer's coefficient of variation: Measure of the variability of discharge of a random sample of a given make, model, and size of micro-irrigation emitter, as produced by the manufacturer and before any field operation or aging has taken place; equal to the ratio of the standard deviation of the discharge of the emitters to the mean discharge of the emitters.
matric potential: Dynamic soil property, and will be near zero for a saturated soil. Matric potential results from capillary and adsorption forces. Formerly called capillary potential or capillary water.
median drop size:
net positive suction head: Head that causes liquid to flow through the suction piping and enter the eye of the pump impeller.
non-saline sodic soil: Soil containing soluble salts that provide an electrical conductivity of saturation extract (ECe) less than 4.0 mmhos/cm and an exchangeable sodium percentage (ESP) greater than 15. Commonly called black alkali or slick spots.
(permanent) wilting point: Moisture content, on a dry weight basis, at which plants can no longer obtain sufficient moisture from the soil to satisfy water requirements. Plants will not fully recover when water is added to the crop root zone once permanent wilting point has been experienced. Classically, 15 atmospheres (15 bars), soil moisture tension is used to estimate PWP.
profile (sprinkler): Chart showing the application rates vs. distance of throw for a sprinkler head.
pump start circuit: Feature on automatic controllers which supplies 24 VAC, which can be used to activate a pump through an external pump start relay.
pump start relay: Low-amperage or electric switch designed for use with pump start circuits.
relative humidity: Ratio of the amount of water vapor present in the atmosphere to the amount required for saturation at the same dry bulb temperature.
riser: Length of pipe which has male nominal pipe threads on each end and is usually affixed to a lateral or sub-main to support a sprinkler or anti-siphon valve.
shutoff head: Pressure head on the outlet side of a pump at which the discharge drops to zero. Maximum pressure a pump will develop at a given speed.
slide gate: Head control valve, which slides on rails, used to control drainage or irrigation water.
slip configuration or slip joint: Connection without threads (of PVC pipe or fittings) which is solvent welded.
sodic soil: Nonsaline soil containing sufficient exchangeable sodium to adversely affect crop production and soil structure.
standard dimension ratio: diameter of a pipe to its wall thickness. Outside diameter is used for OD rated pipe; ID is used for ID rated pipe. Certain dimension ratios have been selected by convention and standards to be used for construction of pipe. These dimension ratios are referred to as standard dimension ratios.
static head: Vertical distance between water source and discharge water levels in a pump installation.
Station: Circuit on a controller which has the ability to be programmed with a run time unique and separate from other circuits and provides power to one or more remote control valves (or valve-in-head sprinklers).
subsurface drip irrigation: Application of water below the soil surface through emitters, with discharge rates generally in the same range as drip irrigation. The method of water application is different from and not to be confused with sub-irrigation where the root zone is irrigated by water table control.
swing joint: Threaded connection of pipe and fittings between the pipe and sprinkler which allows movement to be taken up in the threads rather than as a sheer force on the pipe. Also used to raise or lower sprinklers to a final grade without plumbing changes.
system capacity, gross irrigation: Ability of an irrigation system to deliver the net required rate and volume of water necessary to meet crop water needs plus any losses during the application process. Crop water needs can include soil moisture storage for later plant use, leaching of toxic elements from the soil, air temperature modification, crop quality, and other plant needs.
Tensiometer: Instrument, consisting of a porous cup filled with water and connected to a manometer or vacuum gauge, used for measuring the soil-water matric potential.
thrust block: Normally, concrete poured in place at changes in direction of water flow in piping systems to prevent movement of the pipe.
Turgid: State of a plant cell when the cell wall is rigid due to the hydrostatic pressure of liquid in the cell.
uniformity coefficient (Christiansen's): Measure of the uniformity of irrigation water application. The average depth of irrigation water infiltrated minus the average absolute deviation from this depth, all divided by the average depth infiltrated.
voids ratio: Ratio of the volume of voids (pores) to the volume of soil.
volute: Refers to the flow path of water and its associated pump casing as it leaves the impeller of a pump.
weir: Flow measuring device for open-channel flow. Weirs can be either sharp-crested or broad-crested. Flow opening may be rectangular, triangular, trapezoidal (cipolletti), or specially shaped to make the discharge linear with flow depth (sutro weir). Calibration is based on laboratory ratings.
March 29, 2017, 6:07 am PDT
Website problems, report a bug.
LO financially supports many asssociations through either the payment of dues, conference exhibits and/or discounted advertising
Last Updated 03-20-17