AC Pipe

Asbestos-cement pipe was commonly used for buried pipelines. It combines strength with light weight and is immune to rust and corrosion.



A fitting that makes it possible to join different kinds of pipes together in the same run.


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.


Advance Time

Time required for a given stream of irrigation water to move from the upper end of a field to the lower end.


Aeration Capacity

Volume fraction of air filled pores in a soil at field capacity.


Air Gap

Physical separation of the supply pipe by at least two pipe diameters (never less than one inch) vertically above the overflow rim of the receiving vessel. In this case line pressure is lost. Therefore, a booster pump is usually needed downstream, unless the flow of the water by gravity is sufficient for the water use. With an air gap there is no direct connection between the supply main and the equipment. An air gap may be used to protect against a contaminant or a pollutant, and will protect against both back-siphonage and backpressure. An air gap is the only acceptable means of protecting against lethal hazards.


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.


Allowable Depletion

That part of soil moisture stored in the plant root zone managed for use by plants, usually expressed as equivalent depth of water in acre inches per acre, or inches.


Allowable Stress Factor

Coefficient used to modify reference evapotranspiration to reflect the water use of a particular plant or group of plants particularly with reference to the water stress.


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.



An aquifer is an underground layer of water-bearing permeable rock or unconsolidated materials (gravel, sand, silt, or clay) from which groundwater can be usefully extracted using a water well.



Portion of a full circle (360° covered by a part circle sprinkler).



Surface included within a set of lines. In irrigation, usually used to describe a surface of land or cross section of pipe.


Automatic Drain Valve

Spring loaded valve that automatically opens and drains the line when the pressure drops to near zero.


Available Soil Moisture

Difference at any given time between the actual soil moisture content in the root zone soil and the wilting point.


Available Water

Portion of water in a soil that can be readily absorbed by plant roots. It is the amount of water released between in situ field capacity and the permanent wilting point.



Any unwanted flow of used or non-potable water or substance from any domestic, industrial or institutional piping system into the pure, potable water distribution system. The direction of flow under these conditions is in the reverse direction from that intended by the system and normally assumed by the owner of the system.


Backflow Prevention Device

[BPD] Safety device which prevents the flow of water from the water distribution system back to the water source.


Back Pressure

Increase of pressure in the downstream piping system above the supply pressure at the point of consideration which would cause, or tend to cause, a reversal of the normal direction of flow.


Back Siphonage

Reversal of flow (backflow) due to a reduction in system pressure which causes a negative or sub-atmospheric pressure to exist at a site in the water system.


Basic Intake Rate (Of Soil)

Rate that (irrigation) water enters the soil at the surface.


Basin Irrigation

Irrigation by flooding areas of level land surrounded by dikes. Used interchangeably with level border irrigation, but usually refers to smaller areas.


Best Efficiency Point

Highest efficiency on a pump characteristic curve.


Blaney-Criddle Method

Air temperature based method to estimate crop evapotranspiration.


Bog Coefficient

Inverse of scheduling coefficient but using the wettest 1% window instead of the driest. Gives no indication of the location of dry areas.


Border Dike

Earth ridge or small levee built to guide or hold irrigation or recharge water in a field.


Border Ditch

Small excavation used as a border of an irrigated strip or plot with water being spread from one or both sides.


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.


Brake Horsepower

Power required to drive a pump.



Water emission device that tends to bubble water directly to the ground or that throw water a short distance, on the order of one foot, (300 mm) before water contacts the ground surface.


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.



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.


Capillary Radius

Aditional wetted radius in soil profile beyond surface wetted radius for point source emitters.


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.


Carryover Soil Moisture

Moisture stored in the soil within the root zone during the winter, at times when the crop is dormant, or before the crop is planted. This moisture is available to help meet water needs of the next crop to be grown.


Catch Can Grid

Containers spaced at regular intervals for collecting water for use in a water audit (sprinkler profile test).


Cation Exchange Capacity

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.



Process where pressure in the suction line falls below the vapor pressure of the liquid, vapor is formed and moves with the liquid flow. These vapor bubbles or "cavities" collapse when they reach regions of higher pressure on their way through pumps.


Center Pivot Irrigation

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.


Centrifugal Pump

Pump consisting of rotating vanes (impeller) enclosed in a housing and used to impart energy to a fluid through centrifugal force.


Check, Check Structure

Structure to control water depth in a canal, ditch or irrigated field.


Check Basin Irrigation

Irrigation by flooding areas of level land surrounded by dikes. Used interchangeably with level border irrigation, but usually refers to smaller areas.


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 Valve

Valve used in a pipeline which allows flow in only one direction.



Application of chemicals (including fertilizers) to crops through an irrigation system by mixing them with the irrigation water.


Circuit Breaker

Also called breaker. - a device for interrupting an electric circuit to prevent excessive current, as that caused by a short circuit, from damaging the apparatus in the circuit or from causing a fire.


Circular Mil

Unit of measure used to report the cross sectional area of a wire conductor


Coefficient Of Runoff

Runoff coefficient used in the rational method of predicting a design peak runoff rate. It helps to characterize runoff rate from a watershed area.



Attraction of water molecules to each other. Attraction of like substances to one another. In soils, it is the process that forms a film of water around soil solids.


Compensating Emitter

Emitter designed to discharge water at a near constant rate over a wide range of lateral line pressures.


Compression Fitting

A brass or plastic fitting used to join pipe by tightening two nuts that force a ring like ferrule into the fitting to assure a tight seal.


Consumptive Use

Total amount of water taken up by vegetation for transpiration or building of plant tissue, plus the unavoidable evaporation of soil moisture, snow, and intercepted precipitation associated with vegetal growth.


Continuous-Flow Irrigation

System of irrigation water delivery where each irrigator receives the allotted quantity of water continuously.


Continuous Flushing Emitter

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.


Control Structure

Water regulating structure, usually for open channel flow conditions.



An electric timing device that operates each (irrigation) zone for a predetermined time and frequency.


Conveyance Efficiency

Ratio of the water delivered, to the total water diverted or pumped into an open channel or pipeline at the upstream end.


Conveyance Loss

Loss of water from a channel or pipe during transport, including losses due to seepage, leakage, evaporation, and transpiration by plants growing in or near the channel.


Corporation Stop (Valve)

Quarter turn valve similar to a ball valve with two exceptions. Internally there is a circular disk rather than a ball, and there is no attached handle. A corporation stop is located at the tap-in; it is usually made of brass and is installed using a special tool that doesn't require shutting off the water supply.


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.


Coupler Or Coupling

Device, either self-sealed or mechanically sealed, that connects the ends of two lengths of pipe or pipe to a hose.


Crop Coefficient

Coefficient used to modify reference evapotranspiration to reflect the water use of a particular plant or group of plants particularly with reference to the plant species.


Crop Evapotranspiration

Amount of water used by the crop in transpiration and building of plant tissue, and that evaporated from adjacent soil or intercepted by plant foliage. It is sometimes referred to as consumptive use. Crop evapotranspiration is the quantitative amount of ET within the cropped area of a field, and which is associated with growing of a crop.Same as plant water requirement.


Cross Connection

Any actual or potential connection or structural arrangement between a public or private potable water system and any other source or system through which it is possible to introduce into any part of the potable system any used water, industrial fluids, gas, or substance other than the intended potable water with which the potable system is supplied. By-pass arrangements, jumper connections, removable sections, swivel or change-over arrangements or other "temporary" arrangements through which backflow could occur are considered to be cross-connections. See also Backflow.


Crop Water Stress Index

Index of moisture in a plant compared to a fully watered plant, measured and calculated by a CWSI instrument. Relative humidity, solar radiation, ambient air temperature, and plant canopy temperature are measured.


Cumulative Intake

Depth of water absorbed by soil from the time of initial water application to the specified elapsed time.


Curb Stop Valve

The curb stop valve is located at the property line; it controls the flow of water to the residence. The curb stop is similar to the corporation stop but it is used to shut off the water for repairs, nonpayment of water bills, or flooded basements. Since the corporation stop is usually inaccessible, the curb stop is used as the isolation valve. The curb stop is in an access box, and a long-handled wrench or "key" is used to reach the valve.


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.


Cycle Time

Length of water application periods, typically used with surge irrigation.


Deep Percolation

Movement of water downward through the soil profile below the root zone that cannot be used by plants.


Deficit Irrigation

Irrigation water management alternative where the soil in the plant root zone is not refilled to field capacity in all or part of the field.


Deep Percolation Percentage

Ratio of the average depth of irrigation water infiltrated and drained out of the root zone to the average depth of irrigation water applied.


Degree Of Hazard

The type of backflow preventer used to prevent backflow from occurring at the point of a cross-connection depends on the type of substance which may flow into the potable water supply. A pollutant is considered to be any substance which would affect the color or odor of the water, but would not pose a health hazard. This is also considered a non-health hazard. A substance is considered a health hazard if it causes illness or death if ingested. This health hazard is called a contaminant.


Delivery Box (Irrigation)

Structure diverting water from a canal to a farm unit often including measuring devices. Also called delivery site, delivery facility, and turnout.


Delivery Loss

Loss of water from a channel or pipe during transport, including losses due to seepage, leakage, evaporation, and transpiration by plants growing in or near the channel.Preferred term is conveyance loss.


Demand Irrigation

Procedure where each irrigator may request irrigation water in the amount needed and at the time desired.


Diameter Of Throw

Average diameter of the area wetted by an irrigation sprinkler operating in still air.


Distribution Uniformity

Measure of the uniformity of irrigation water over an area.


Disturbed Soils

Soils with soil profiles that have been altered because of earth-moving activities


Diversion Box

Structure built into a canal or ditch for dividing the water into predetermined portions and diverting it to other canals or ditches.


Diversion Dam

Barrier built in a stream for the purpose of diverting part or all of the water from the stream into a canal.


Double Check Valve Assembly

Two internally loaded, independently operating check valves together with tightly closing resilient seated shut-off valves upstream and downstream of the check valves. Additionally, there are resilient seated test cocks for testing of the assembly. The DC may be used to protect against a pollutant only. However, this assembly is suitable for protection against either backsiphonage or backpressure.


Drip Irrigation

Also known as microirrigation or trickle irrigation is an irrigation method which minimizes the use of water and fertilizer by allowing water to drip slowly to the roots of plants, either onto the soil surface or directly onto the root zone, through a network of valves, pipes, tubing, and emitters.



Period of dryness especially when prolonged that causes extensive damage to crops or prevents their successful growth.


Dry Weight (Of Soil Sample)

Oven dry weight of a soil sample.


Dynamic Head

Specific energy in a flow system.


Dynamic Pressure

Measure of water pressure with the water in motion (also known as working pressure).


Effluent Irrigation

Land application of treated wastewater for irrigation and beneficial use of nutrients.


Electrical Resistance Block

Block made up of various materials containing electrical contact wires that is placed in the soil at selected depths to measure soil moisture content (tension). Electrical resistance, as affected by moisture in the block is read with a meter.


Emission Point

Location where water is discharged from an emitter.


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.



Small micro-irrigation dispensing device designed to dissipate pressure and discharge a small uniform flow or trickle of water at a constant discharge, which does not vary significantly because of minor differences in pressure head. Also called a "dripper" or "trickler".



Physical process by which a liquid is transformed to the gaseous state, which in irrigation generally is restricted to the change of water from liquid to vapor. Occurs from plant leaf surface, ground surface, water surface and sprinkler spray.



Combination of water transpired from vegetation and evaporated from the soil and plant surfaces.



Application of nutrients through an irrigation system.


Field Capacity

Moisture remaining in a soil following wetting and natural drainage until free drainage has practically ceased.


Final Infiltration Rate

Rate that (irrigation) water enters the soil at the surface.



Acronym for female iron pipe thread.



Any connector (except a valve) that lets you join pipes of similar or dissimilar size or material in straight runs or at an angle.


Flood Irrigation

Method of irrigation where water is applied to the soil surface without flow controls, such as furrows, borders or corrugations.


Flow Rate

Rate of flow or volume per unit period of time.


Foot Valve

Check valve used on the bottom of the suction pipe to retain the water in the pump when it is not in operation.


Free Drainage

Movement of water by gravitational forces through and below the plant root zone. This water is unavailable for plant use except while passing through the soil.


Frequency Distribution

Measurement and presentation of various fractions of total water applied for selected depth ranges referenced to average depth applied.


Frost Protection

Applying irrigation water to affect air temperature, humidity, and dew point to protect plant tissue from freezing. The primary source of heat (called heat of fusion) occurs when water turns to ice, thus protecting sensitive plant tissue.


Frost Heave

The upthrust of soil caused when moist soil freezes. Supply lines that do not extend below the frost line are subject to frost heave.


Frost Line

The maximum depth frost normally penetrates the soil during the winter. This depth varies from area to area depending on location and climate.


Friction Loss

Amount of pressure lost as water flows through an irrigation system (due to friction against the pipe walls).Also, referred to as pressure loss.


Full Irrigation

Management of water applications to fully replace water used by plants over an entire field.



Small channel for conveying irrigation water down slope across the field. Sometimes referred to as a rill or corrugation.


Furrow Irrigation

Method of surface irrigation where the water is supplied to small ditches or furrows for guiding across the field.


Furrow Stream

Stream flow in a furrow, corrugation or rill.



A safety device, located in an electrical box that shuts off power when a circuit overloads.


Gate, Slide Gate

Device used to control the flow of water to, from, or in a pipeline or open channel.


Gated Pipe

Portable pipe with small gates installed along one side for distributing irrigation water to corrugations or furrows.


Gear Drive Sprinkler

Sprinkler containing gears as part of its rotational drive mechanism.


Gravitational Water

Soil water that moves into, through, or out of the soil under the influence of gravity.


Gross Irrigation

Total irrigation requirement including net crop requirement plus any losses incurred in distributing and applying and in operating the system.


Ground Water

Water occurring in the zone of saturation in an aquifer or soil.


Growing Season

Period, often the frost-free period, during which the climate is such that crops can be produced.


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.


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.


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 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.


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 - 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.


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.



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


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.



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.


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.



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.


Impact Drive

Sprinkler which rotates using a weighted or spring-loaded arm which is propelled by the water stream and hits the sprinkler body, causing movement.


Impact Power

Rate at which drops deliver kinetic energy to the soil.


Impact Rate

Impact power per unit area.



Process of water movement through the soil surface into the soil matrix.


Infiltration Rate

Volume of water infiltrating through a horizontal unit area of soil surface at any instant.



Device used to measure the infiltration rate / intake rate of water into soil.


Inrush Current

Current necessary to initially open the solenoid valve.


Intake Family

Grouping of intake characteristics into families based on field infiltrometer tests on many soils.


Intake, Initial

Depth (rate) of water absorbed by a soil during the period of rapid or comparatively rapid intake following initial application.



Part of precipitation or sprinkler irrigation system applied water caught on the vegetation and prevented from reaching the soil surface.


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.


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.


Iron Pipe Size

One of several systems which specify pipe dimensions.


Irrecoverable Water Loss

Water loss that becomes unavailable for reuse through evaporation, phreatophytic transpiration, or ground-water recharge that is not economically recoverable.



Intentional application of water to the soil, usually for the purpose of crop production (reclaiming soils, temperature modification, improving crop quality).


Irrigation Design

Plan of an irrigation system with pipe sizing, head layout and valve location.


Irrigation District

Cooperative, self-governing, semipublic organization set up as a subdivision of a state or local government to provide irrigation water.


Irrigation Frequency

Measure of the number of irrigations per unit time.


Irrigation Interval

Time between irrigation events. Usually considered the maximum allowable time between irrigations during the peak ET period.


Irrigation Period

Time that it takes to apply one irrigation to a given design area during the peak consumptive-use period of the crop being irrigated.


Irrigation Sagacity

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.


Irrigation Schedule

Procedure of establishing and implementing the time and amount of irrigation water to apply.


Irrigation Set

Area irrigated at one time within a field.


Irrigation Slope

Elevation difference along the direction of irrigation. Sometimes called irrigation grade.


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. 


Jockey Pump

Usually a small pump used to provide pressure and flow in a multi-pump system


Junction Box

Is a container for electrical junctions, usually intended to conceal them from sight and to some extent to eliminate tampering.


Lag Time (Flood Irrigation)

Period between the time that the irrigation stream is turned off at the upper end of an irrigated area and the time that water disappears from the surface at the point or points of application.



Secondary or side channel, ditch or conduit. Also call "branch drain" or "spur".


Lath Box

Wooden box that is placed in a ditch bank to transfer water from an irrigation ditch to the field to be irrigated (preferred term is spile).



Removal of soluble material from soil or other permeable material by the passage of water through it.



Linear dimension used to describe the quantity / amount / distance of pipe, conductor or similar material in various equations.


Length Of Run

Distance water must flow in furrows or borders over the surface of a field from the head to the end of the field.


Limited Irrigation

Management of irrigation applications to apply less than enough water to satisfy the soil water deficiency in the entire root zone. Sometimes called " deficit" or "stress irrigation".


Looped Circuit

Piping system, usually a main line, that closes back on itself in a loop, thus providing water to any location from two routes.


Low Head Drainage

Condition in which water drains partially or completely out of the lateral line through the sprinkler head after each irrigation cycle is completed.


Main (Mainline)

Water delivery pipelines that supply water from the control station to the manifolds.


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.


Master Valve

Valve used to protect the landscape from flooding in case of a ruptured main or malfunctioning downstream valve. The master valve is installed on the mainline after the backflow preventer (in some systems).


Matric Potential

Dynamic soil property and will be near zero for a saturated soil. Matric potential results from capillary and adsorption forces. This potential was formerly called capillary potential or capillary water.


Maximum Allowable Deficiency

Term used to estimate the amount of water that can be used without adversely affecting the plant and is defined as the ratio of readily available water to available water.


Maximum Application Rate

Maximum discharge at which sprinklers can apply water without causing significant translocation.


Median Drop Size

Diameter where half the sprinkler's water volume falls in drops smaller, and half falls in drops larger than the median size.
Drop size where 50%of the water volume occurs in drops greater than this size.


Micro Irrigation

Also known as drip irrigation or trickle irrigation is an irrigation method which minimizes the use of water and fertilizer by allowing water to drip slowly to the roots of plants, either onto the soil surface or directly onto the root zone, through a network of valves, pipes, tubing, and emitters.


Mist Irrigation

Method of micro-irrigation in which water is applied in very small droplets.


Mixed Flow Pump

Centrifugal pump in which the pressure is developed partly by centrifugal force and partly by the lifting action of the impellers on the water.


Moisture Deficit, Soil Moisture Depletion

Difference between actual soil moisture and soil moisture held in the soil at field capacity.


Moisture Meter

Device that monitors or measures soil water content or tension.


Moisture Sensor

Device that monitors or measures soil water content of tension.


Multistage Pump

Pump having more than one impeller mounted on a single shaft.


Net Irrigation

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.


Net Positive Suction Head

Head that causes liquid to flow through the suction piping and enter the eye of the pump impeller.



A 12-inch or shorter pipe that has threads on both ends used to join fittings. A close nipple has threads that run from both ends to the center.


Nominal Size

Named size which is usually not the actual dimensions of the product. i.e. a half inch schedule 40 pipe is not 1/2 inch ID or OD.


Nonbeneficial Use

Water utilized in plant growth which can not be attributed as beneficial.


Nonconsumptive Use

Water that leaves the selected region and not considered consumptive. Examples are runoff, deep percolation, and canal spills.
Nonpoint source pollution Pollution originating from diffuse areas (land surface or atmosphere) having no well-defined source.


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.



Final orifice through which water passes from the sprinkler or emitter to the atmosphere.


Operating Pressure

Pressure at which a system of sprinklers operates, usually measured at the base or nozzle of a sprinkler.


Opportunity Time

Time that water inundates the soil surface with opportunity to infiltrate.


Orchard Valve

Outlet valve installed inside a short vertical pipe (riser) with an adjustable cover or lid for flow control. Similar to an alfalfa valve, but with lower flow capacity. Typically used in basin irrigation.


Osmotic Potential

Potential attributable to the presence of solutes in the soil- in other words, to the soil solution.


Oven Dry

Refers to soil samples that have been dried in an oven at 105°C for 24 hours.



An area, which is watered by two or more sprinklers.


Percentage Fines

Percentage of water volume falling in fine (< 1 mm in diameter drops) mist. Term also used relative to soil particle size.



Beneficial deep percolation-leaching. {in.} is a beneficial use when it leaches salts from the root zone to a level required for acceptable crop production.


Percolation Rate

Rate at which water moves through porous media, such as soil.


Performance Curve

Graph showing the capability of a product with varying inputs. (i.e. the dynamic head of a pump as it varies with discharge.


Permanent Irrigation

Irrigation having underground piping with risers and sprinklers. Preferred term is stationary sprinklers.


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.



Qualitatively, the ease with which gases, liquids, or plant roots penetrate or pass through a layer of soil.


Pipe Dope

Common name for commercial products used to apply to pipe fittings to assist in the appropriate fit of the threaded joints.


Pipe Joint Compond

A material applied to steel pipe threads to ensure a watertight or airtight seal. Also called pipe dope.


Pipe Thread Tape

A synthetic pipe thread wrapping that seals a joint.


Pitot Tube

Small "L" shaped tube which can be attached to a pressure gage or other measuring device to measure the velocity head of water discharging from a nozzle or flowing in a pipe.



Flexible (usually black) plastic material used to make irrigation pipe and other items.



Semi-rigid plastic material used to make irrigation pipe and other items.


Pop-Up Spray Head

A sprinkler head that is generally set flush with the soil. These heads contain a stem that rises when the water is turned on.



Volume of pores in a soil sample relative to the total volume of the sample.


Positive Displacement Pump

Pump that moves a fixed quantity of fluid with each stroke or rotation, such as a piston or gear pump.


Potable Water

Domestic or drinking water. It can be used as a source of irrigation water, but once water enters an irrigation system (and passes through the backflow device) it is no longer considered potable.



The force exerted over a surface divided by its area (Webster) In irrigation, pressure usually describes the amount of energy available to move water through a pipe, sprinkler or emitter.


Pressure Due To Surge

Water pressure caused due to changes in water velocity in a pipe system. Also referred to as surge pressure.


Pressure Gauge

A device that can be attached to your home's water system to measure the psi (pounds per square inch) of static water pressure.


Pressure Loss

Amount of pressure lost as water flows through a system.


Pressure Rating

Estimated maximum internal pressure that can be continuously exerted in a pipe or container with a high degree of certainty that it will not fail.


Pressure Regulator

Device which maintains constant downstream operating pressure (immediately downstream of the device) which is lower than the upstream pressure.


Pressure Tank

Enclosed container attached to a water system usually containing an air pocket so that it behaves as a temporary water supply.


Pressure Vacuum Breaker

Backflow device configured with a spring loaded float and an independent spring loaded check valve.Check valve which is designed to close with the aid of a spring when flow stops. It also has an air inlet valve which is designed to open when the internal pressure is one psi above atmospheric pressure so that no non-potable liquid may be siphoned back into the potable water system. Being spring loaded it does not rely upon gravity as does the atmospheric vacuum breaker. This assembly includes resilient seated shut-off valves and test cocks. The PVB must be installed at least twelve (12) inches above all downstream piping and outlets. The PVB may be used to protect against a pollutant or contaminant, however, it may only be used to protect against backsiphonage. It is not acceptable protection against backpressure.


Propeller Pump

Pump which develops most of its head by the lifting action of vanes on the water.


Pump Column

Pipe through which water from well pumps (vertical turbine impellers) is conveyed to the ground surface (pump discharge head).


Pump Efficiency

Ratio of the water power produced by the pump, to the power delivered to the pump by the power unit.


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.



Polyvinylchloride (PVC) pipe is the most common accepted type of plastic drain pipe. PVC is sometimes also used for supply pipes in irrigation installations.


Quick Coupling Valve

Permanently installed valve which allows direct access to the irrigation mainline. A quick coupling key is used to open the valve.


Radial Flow Pump

Centrifugal pump that uses diffuser vanes to transform the velocity head into pressure head.Commonly called a "turbine pump."


Radius Of Throw

Distance from the sprinkler head to the furthest point of water application and is used only for heads with circular wetting patterns.


Rain Gauge

Device such as a graduated tube used to measure the amount of rainfall.


Rain Sensor

Device to measure rainfall.


Rain Shut-Off Device

Device which prevents voltage from the controller from activating the valves when a preset amount of rain falls.


Rainfall Intensity

Rate of rainfall for the design storm frequency and for the time of concentration of the drainage area. (Used in rational method to compute runoff.)


Rational Equation

Equation used to predict the runoff from a watershed.
Readily Available Water - Portion of available water that is more readily available for plant usage. It varies with plant type.


Reclaimed Water

Water that has been collected after an original use for reuse.


Rectangular Spacing

Sprinklers are spaced in a rectangular pattern.


Reduced Pressure Assembly

Consists of two internally loaded independently operating check valves and a mechanically independent, hydraulically dependent relief valve located between the check valves. This relief valve is designed to maintain a zone of reduced pressure between the two check valves at all times. The RP also contains tightly closing, resilient seated shut-off valves upstream and downstream of the check valves along with resilient seated test cocks. This assembly is used for the protection of the potable water supply from either pollutants or contaminants and may be used to protect against either backsiphonage or backpressure.


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.



Electrical or electronic device which uses a signal current to actuate a separate electrical circuit.



Operation when the pop-up riser of a sprinkler such as a spray head or rotor returns to the case in the ground. Also called pop-down.



Hindrance to current flow in a given circuit.


Reynolds Number

Dimensionless number used to characterize flow of water.



Area of flowing streams that lies between the normal water line and some defined high water line.



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.


Root Zone

Area of the soil from which the crop roots extract water and nutrients.


Rotational Speed

Number of revolutions made per unit time (usually minutes) by a shaft or other object.


Rotor Sprinkler

Sprinkler that rotates, but may more specifically refer to a gear driven sprinkler


Row Spacing

Distance between adjacent rows of sprinklers.



Portion of precipitation, snow melt or irrigation, that flows over the soil, eventually making its way to surface water supplies.


Runoff Rate

Water which is not absorbed by the soil and drains to another location. Runoff occurs when water is applied in excessive amounts or too quickly.


Run Time

Length of time to operate an irrigation system or an individual zone.


Run Time Multiplier

Multiplier used to compensate for the lack of perfect uniformity in a sprinkler system.


Sail Index

Cross-sectional area per unit volume of water of the drop comprising the sprinkler spray.



Refers to the amount of salts dissolved in soil water.



Method of specifying the dimensions and thus the allowable operating pressure of pipe. For a specific schedule rating, the wall thickness remains relatively constant for different pipe diameters, resulting in lower allowable operating pressures for larger diameter pipe.



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.


Scheduling Coefficient

A number that relates to the uniformity of coverage and how to operate the system to adequately irrigate the entire turf area. It indicates the amount of extra watering time needed to adequately irrigate the driest areas..


Service Line

Section of piping connecting larger municipal supply line with water meter.


Service Panel

An electrical box that contains either fuses or circuit breakers. Power from the utility enters the service panel, where it's divided up into branch circuits. Also referred to as a panel box or a main panel.


Set Time

Amount of time required to apply a specific amount of water during one irrigation to a given area, typically refilling the plant root zone to field capacity minus expected rainfall.


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.


Single Leg Profile

Precipitation rate profile of an individual sprinkler head operating at a known, constant pressure.



Closed conduit used to convey water across localized minor elevation raises in grade. It generally has end sections below the middle section. A vacuum pump is commonly used to remove air and keep the siphon primed. The upstream end must be under the water surface. Both ends must be under water, or the lower end must be closed to prime the siphon.


Siphon Tube

Relative short, light-weight, curved tube used to convey water over ditch banks to irrigate furrows or borders.



Mineral portion of soil have particle sizes ranging from 0.05 to 0.002 mm in diameter.


Slide Gate

Head control valve, which slides on rails, used to control drainage or irrigation water.
Slip Joint Or Slip - ConfigurationConnection without threads (of PVC pipe or fittings) which is solvent welded.


Soil Profile

A vertical cross section through a soil which shows any layers or horizons of which the soil is composed.


Soil Reservoir Capacity

Preferred term Plant Available Water.


Soil Water (Moisture)

 All water stored in the soil.


Soil Water Characteristic Curve

Soil-specific relationship between the soil-water matric potential and soil-water content.


Soil Water Content

Amount of water in a given volume (or weight) of soil.



Electromagnet which is connected to a controller and facilitates the opening and closing of automatic control valves (or valve-in-head sprinklers).


Solid Set Irrigation System

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.


Species Factor

Factor or coefficient used to adjust reference evapotranspiration to reflect plant 


Specific Gravity

Ratio of a substance's density (or specific weight) to that of some standard substance such as water. For liquids, the standard is water at sea level and 60°F (SP. GR. = 1).



Conduit, made of lath, pipe or hose, placed through ditch banks to transfer water from an irrigation ditch to a field.


Spray Irrigation

Application of water by a small spray or mist to the soil surface, where travel through the air becomes instrumental in the distribution of water.


Sprinkler Distribution Pattern

Water depth-distance relationship measured from a single sprinkler head.


Sprinkler Irrigation

Method of irrigation in which the water is sprayed, or sprinkled, through the air to the ground surface.


Static Head

Energy associated with a static liquid system composed of elevation and pressure components.



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).


Stationary Sray Head

Because these heads do not move, rotate or pop-up they are the most maintenance free type of spray head.


Stress Irrigation

Management of irrigation water to apply less than enough water to satisfy the soil water deficiency in the entire root zone. Preferred term is Limited Irrigation Or Deficit Irrigation.



Applying irrigation water below the ground surface either by raising the water table or by using a buried perforated or porous pipe system that discharges water directly into the plant root zone. ...


Submersible Pump

Pump where the motor and pump are submersed below the water surface.


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.


Suction (Static) Lift

Vertical distance between the elevation of the surface of the water source and the center of the pump impeller.


Surface Irrigation

Type of irrigation where water is distributed to the plant material by a ground surface distribution network possibly including rows or dikes.


Surge Irrigation

Surface irrigation technique wherein flow is applied to furrows (or less commonly, borders) intermittently during a single irrigation set.


Surge Pressure

 Water pressure caused by changes in water velocity in a pipe system.



A technique used to produce watertight joints between copper pipe fittings. A pipe and fittings are cleaned, coated with flux


Swing Check (Valve)

 Valve used in a pipeline which allows flow in only one direction.


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

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.


Tail Water

 Surface runoff resulting from crop irrigation. Irrigation practices such as flood irrigation and sprinkler irrigation can result in applied water in excess of the infiltration rate of the soil. Sloped fields can allow for the excess water to run off the field, and discharge to a drainage channel or natural water body. Tailwater can carry pollutants such as silt, nutrients (from fertilizers), and pesticides.


Thrust Block

Normally, concrete poured in place at changes in direction of water flow in piping 
systems to prevent movement of the pipe.



The state of aggregation of a soil especially in relation to its suitability for crop growth.



Term used to describe the duration of an operation, e.g. an irrigation event.


Timer Or Controller

A device that switches on irrigation valves and lets them run for a preset time before switching them off.


Transition Fitting

Any one of several fittings that joins pipes made of dissimilar materials, such as copper and plastic, plastic and cast iron, etc.



Movement of water to areas other than where it was applied.



Liquid movement of water from the soil, into the roots, up the plant stems, and finally out of the plant leaves into the air as vapor.


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. Travelers are also called cable-tow, hard hose and hose drag.


Triangular Spacing

Sprinklers are spaced in a triangular pattern.


Trickle Irrigation

Also known as drip irrigation or microirrigation is an irrigation method which minimizes the use of water and fertilizer by allowing water to drip slowly to the roots of plants, either onto the soil surface or directly onto the root zone, through a network of valves, pipes, tubing, and emitters.


Turbine Pump

Pump having one or more stages, each consisting of an impeller on a vertical shaft, surrounded by stationary and usually symmetrical guide vanes. Combines the energy-imparting characteristics of axial-flow and propeller pumps.


Turbulent Flow

Flow in which the fluid particles move in an irregular random manner, in which the head loss is approximately proportional to the second power of velocity.



State of a plant cell when the cell wall is rigid due to the hydrostatic pressure of liquid in the cell.


Unavailable Soil Water

Portion of water in a soil held so tightly by adhesion and other soil forces 
that it cannot be absorbed by plants rapidly enough to sustain growth.



Pipe fitting used to connect two lengths of pipe to facilitate adding a tee.


Unsaturated Zone

Part of the soil profile in which the voids (pore spaces) are not completely filled with water.



Device to control flow


Vapor Pressure Head

Pressure head at which the liquid (water) will vaporize or boil at a given temperature.



Is the speed at which water moves through the system (pipe).


Vertical Turbine Pump

Pump having one or more stages, each consisting of an impeller on a vertical shaft, surrounded by stationary and usually symmetrical guide vanes. Combines the energy-imparting characteristics of axial-flow and propeller pumps.



Refers to the flow path of water and its associated pump casing as it leaves the impeller of a pump.


Water Allotment

A method to accurately and fairly estimate a total volume of water that should be allocated to a site.


Water Allotment Adjustment Factor

Factor used in the equation to predict Water allotment.


Water Hammer

Shock wave created when the flow of water in a piping system suddenly stops (or changes speed). Usually the result of a fast-closing (or opening) valve.


Water Meter

Device used to measure to flow of water.


Water Rights

State administered legal rights to use water supplies derived from common law, court decisions, or statutory enactments.


Water Table

Upper surface of a saturated zone below the soil surface where the water is at atmospheric pressure.


Water Window

Time of day available for irrigation to occur.



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.


Wet Weight (Of Soil Sample)

Weight of soil sample and included soil moisture.


Wetted Area

Surface area wetted at completion of irrigation.


Wetted Diameter

Average diameter of the area wetted by an irrigation sprinkler operating in still air. Preferred term diameter of throw.


Wetting Agent

Chemical used to reduce the surface tension of a liquid causing it to make better contact with the desired target.


Wiper Seal

A rubber or plastic gasket in pop-up spray heads that keeps dirt and debris out of the mechanism.


Wilting Point

Moisture content of the soil after the plant can no longer extract moisture at a sufficient rate for wilted leaves to recover overnight or when placed in a saturated environment.



Process of removing water from the irrigation system before the onset of freezing temperatures.


Wire Gauge

(One of several) standard units of measure for wire size. The larger the gauge number, the smaller the wire.



Work done by a force on a particle is defined as the product of the magnitud e of the force and the distance through which the particle moves. In hydraulic systems, it can be calculated as the product of the pressure and flow rate.


Working Pressure

Pressure of the irrigation system during operating. Synonymous with dynamic pressure.


Working Storage

Amount of water available in the soil profile for plant use after consideration of MAD.



Refers to landscaping in ways that do not require supplemental irrigation. It is promoted in areas that do not have easily accessible supplies of fresh water. It encourages the use of native or well adapted plants that are suited to the amount of precipitation available in that particular region.



 Torna inizio pagina

Sapevi che:

Il cervello umano è costituito al 75% d'acqua.


Questo sito utilizza cookie propri e di terze parti anche con finalità commerciali. Continuando a navigare o accedendo a un qualunque elemento del sito senza cambiare le impostazioni dei cookie, accetterai l’utilizzo dei cookie.
Le impostazioni dei cookie possono essere modificate in qualsiasi momento utilizzando il link Privacy Policy presente nel sito, dal quale è possibile negare il consenso all'installazione di qualunque cookie.