The A-Z Netafim Glossary is edited by Netafim University in order to provide you with a common language and smoother communication as well as a training tool to better understand drip irrigation. The Glossary was compiled by Netafim experts based on their experience as well as on many official sources.

a b c d e f g h i j k l m n o p q r s t u v w x y z


advance ratio (AR)
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 good distribution uniformity.

advance time (minutes, sec)
Time required for a given surface irrigation stream to move from one point in the field to another.alkaline (alkali) With relevance to agriculture, soil or water that contains substances that raise the pH value above 7.0 (neutral).

allowable depletion (in., mm)
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. see coefficient

alternative agriculture
A systematic approach to farming intended to reduce agricultural pollution, enhance sustainability, and improve efficiency and profitability. see bio-organic agriculture or sustainable agriculture

application efficiency
application efficiency: see efficiency

application rate
application rate: see precipitation rate

area (in.2, ft2, acres, ha)
In irrigation, usually used to describe a surface of land or cross section of pipe. Area units in common use:
Acre = 4,046.8564 m2 or 0.40468564 hectares.
Hectare (ha) = 10,000 m2 or 2.4710538 acres.
Dunam = 1,000 m2 or 0.1 hectare or 0.24710538 acres.

atmospheric pressure
Absolute pressure measured at any location. Standard atmospheric pressure at sea level is defined as 1 bar (1000 millibar), 14.7 psi or 34.0 ft of water.

available soil moisture
Available soil moisture is the difference in water content of the soil between field capacity and permanent wilting point. This is the soil water that is available for plants to use. By definition, it should be expressed as a percentage, or as a depth in millimeters per meter of soil, because the amount of water available to plants depends on this value and the root depths. same as water holding capacity

available water holding capacity
preferred term is available water

available water storage capacity
preferred term is available water available water



back flow
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.back flush The processes of flowing pressurized water backwards through a filter to remove trapped debris and restore the filtration system for ongoing use.

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
basic intake rate: see intake rate

best management practice
best management practice: see irrigation best management practice

bio-organic agriculture
Bio-Organic Agriculture is a holistic production management system, which promotes and enhances agro-ecosystem health, including biodiversity, biological cycles and soil biological activity. see alternatice agriculture or sustainable agriculture

Blaney-Criddle Method
Air temperature based method to estimate crop evapotranspiration.

branch line
Polyethylene tubing that attaches to the mainline to bring water to a plant or to an area of a zone. see sub main

A bud is a developing part of a plant that will grow into a flower, a new leaf or a stem.



capillary action
The movement of water in the interstices of a porous medium due to capillary forces. Same as capillary flow and capillary migration.

capillary flow
capillary flow: see capillary action

capillary migration
capillary migration: see capillary action

capillary radius
Additional 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.

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.

Application of chemicals (including fertilizers) to crops through an irrigation system by mixing them with the irrigation water. see: Nurigation™ or Fertigation

Full or partial blocking of drip emitters by silt or other suspended solid matter. As a result of clogging the discharge rate of the emitter is reduced or completely zero.

coefficient of retardation
Values describing the hydraulic frictional characteristics of a pipe material.

Various forms of “k” are used to describe constants, coefficients and factors.

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

compensating dripper
compensating dripper: see dripper

Compost is the aerobically decomposed remnants of organic matter. It is used in agriculture, horticulture and landscaping as a soil conditioner and fertilizer. It is also useful for erosion control, land and stream reclamation, wetland construction, and as landfill cover.

continuous flushing dripper
continuous flushing dripper: see dripper

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

An automatic timing device that sends an electric signal for automatic valves to open or close according to a set irrigation schedule.

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.

crop coefficient
crop coefficient: see coefficient

crop evapotranspiration
crop evapotranspiration: see evapotranspiration

crop rooting depth
crop rooting depth: see root zone

crop water requirements
The total water needed for evapotranspiration, from planting to harvest for a given crop in a specific climate regime, when adequate soil water is maintained by rainfall and/ or irrigation so that it does not limit plant growth and crop yield.

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.

crop water use
crop water use: same as plant water requirement and evapotranspiration.

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



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

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.

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. see regulated deficit irrigation

delivery loss
delivery loss: preferred term is conveyance loss

density factor
density factor: see coefficient

density of water
Mass of water per unit volume.

depth of irrigation
Depth of soil affected by an irrigation event.

The volume of water that passes a given point within a given period of time. It is an all-inclusive outflow term, describing a variety of flows. Such as from a pipe to an emitter.

distribution uniformity
Measure of the uniformity of irrigation water over an area.

drip irrigation
An acknowledged irrigation method which minimizes the use of water and fertilizer allowing water to drip slowly and precisely to the roots of plants, either onto the soil surface or sub surface – directly onto the root zone. Drip irrigation is a low-pressure method of irrigation through a network of valves, pipes, tubing and emitters allowing less water loss due to evaporation. Also known as trickle irrigation or microirrigation

drip lateral/ line
The water delivery pipeline or polyethylene pipe that supplies water to the emitters from the main lines or sub-mains.

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 known as emitter or trickler.
click here to download file

dry weight
Oven dry weight of a soil sample.

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



effective precipitation
Portion of total precipitation which becomes available for plant growth.

effective rainfall
Portion of total rainfall which becomes available for plant growth.

application efficiency (Ea, AE) Ratio of the average depth of the irrigation water stored in the root zone to the average depth of irrigation water applied.

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

electrical conductivity
Electrical conductivity is the property of a material to conduct electricity. The ease with which electrical conductivity passes through water is proportional to the salt concentration in the water. Therefore, the higher the EC, the greater the salt concentration is. It is an indirect measure of soil salinity. The electrical conductivity is commonly expressed as deciSiemens per meter (dS/m) and milliSiemens per centimeter (mS/cm). see soil electrical conductivity

emission point
Location where water is discharged from a dripper.

emission uniformity
Index of the uniformity of dripper discharge rates throughout a micro-irrigation system. Takes account of both variations in drippers and variations in the pressure under which the drippers operate. emitter: see dripper

emitter: see dripper

Water movement from a wet soil or plant surface which does not pass through the plant.see transpiration
click here to download file

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



Application of plant nutrients through an irrigation system. also known as Nurigation™

Any of a large number of natural or synthetic materials, including manure and nitrogen, phosphorus, and potassium compounds, spread on or worked into soil to increase its fertility.

field capacity
The maximum amount of water that a soil can hold indefinitely against gravity. Put another way it is the amount of water left in the soil after all the free water has had a chance to drain out through the force of gravity.

A component used to remove particles from the water that might otherwise plug up your emitters. The size of the filter screen is expressed as mesh, with larger numbers denoting smaller openings in the screen. In drip irrigation, the range of size is from 80 to 200 mesh according to the water quality and type of dripper.

final infiltration
final infiltration rate: see intake rate

flood irrigation
The application of irrigation water in which the entire soil surface is covered by ponded water. see surface irrigation

flow rate
Rate of flow or volume per unit period of time.

flushing dripper
Dripper designed to have flushing flow of water to clear the discharge opening every time the system is turned on.

flushing velocity
For proper flushing to occur, the discharge velocity must be high enough to both dislodge and transport particulate matter from the pipelines. In general, flushing velocity should be as high as possible, but never less than 1fps. Higher flushing velocities will aid particle removal and shorten the flushing time needed.

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

friction factor, Christiansen
Friction factor or coefficient used in the Christiansen Procedure to determine pressure loss in a multiple outlet piping system. see lateral friction factor

friction loss
As water moves through tubing, pressure is lost due to friction in the line. A drop in pressure lowers the output of some (non-pressure compensating) emitters or sprayers at the end of the line. Friction loss can increase if the tubing goes up hill or decrease if it goes down hill. To decrease friction, a larger size of tubing can be used.

friction loss
As water moves through an irrigation system, pressure is lost because of turbulence created by the moving water. This turbulence can be created in pipes, valves or fittings. These losses are referred to as friction losses.

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

furrow irrigation
A partial surface-flooding method of irrigation, normally used with clean-tilled crops in which water is applied in furrows or rows of sufficient capacity to contain the design irrigation stream.see surface irrigation



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.

gravity irrigation
An irrigation method in which water is not pumped, but flows in ditches or pipes and is distributed by gravity. also known as gravitational irrigation see surface irrigation

gray water
Domestic wastewater other than those containing human excreta such as sink drainage, washing machine discharge, or bath water.

growing season (days)
Period, often the frost-free period, during which the climate is such that crops can be produced.



head (H) (ft, m) atmospheric pressure (head) (Ha) Value of atmospheric pressure at a specific location and condition.
click here to download file

hectare (ha): see area

high density polyethylene
One of several forms of polyethylene used to make pipe and other irrigation components.

hydraulic conductivity
Soil-water characteristic describing the ability of water to flow through a particular soil.

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

hygroscopic water
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.



Abbreviation for inside diameter, usually of a pipe.

Process of water movement through the soil surface into the soil matrix. see intake rate

infiltration rate
Preferred term is intake rate.

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

Devices to put (inject) fertilizer (as well as pesticides if so desired) into the water of a system.

in-line emitter
Drip emitters that are connected to each other by segments of polyethylene to form the required drip line. Usually available in various combinations of operating pressure, discharge rate and diameter.

in-line valve
Valve placed into the system to allow one part of the system to be turned off. Valuable for flexibility.

Tubing with the drippers (emitters) built into the tubing at set spacings.

intake rate
Rate at which water percolates into the soil after infiltration has decreased to a low and nearly constant value.

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

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

integral emitter
Drip emitters welded to the inner tube as part of the tubing flow path. Usually available in pre-set emitter spacing (depending on the crop), wall thickness, operating pressure and discharge rate.

Lateral movement of water in the upper layer of soil.

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

irrigable area
Area capable of being irrigated, principally based on availability of water, suitable soils, and topography of land.

Became from two Latin words ‘in’ and ‘rigare’ which means ‘to water’. In other terms irrigation is the artificial watering of the land for the purpose of growing crops.

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.

irrigation best management practice
The voluntary irrigation practice that is both economical and practical and is designed to reduce water consumption and protect water quality while maintaining a healthy, functional landscape.

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

irrigation efficiency
irrigation efficiency: see efficiency

irrigation frequency
Measure of the number of irrigations per unit time.

irrigation interval
Average time interval between the commencement of successive irrigations for a given field or area.

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 schedule
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.

irrigation schedule
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.

irrigation scheduling
irrigation scheduling: see schedule or scheduling

irrigation set
Area irrigated at one time within a field.

irrigation set time
irrigation set time: see set time

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

irrigation system
Set of components which includes (may include) the water source, water distribution network, control components and possibly other general irrigation equipment.

irrigation water requirement
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. same as gross irrigation requirement



Water delivery pipeline that supplies irrigation water from the main line to sprinklers or emitters.

lateral friction factor
lateral friction factor: see friction factor

lateral movement
lateral movement: see interflow

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.

Acronym for Low Energy Precision Application.

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”.

line source
Continuous source of water emitted along a line.

line source dripper
Water is discharged from closely spaced perforations or a porous wall along the tubing.

line source emitter
line source emitter: see emitter

long-path dripper
Dripper which employs a long capillary sized tube or channel to dissipate pressure.

long-path emitter
long-path emitter: see emitter

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 Energy Precision Application
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.



main/ mainline
Pipe which supplies water from the point of connection to the control valves.

Pipeline that supplies water to the laterals.

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.

micro sprinkler
A spinner type watering device that is available in a variety of styles and configurations and like drip emitters, operate at low-pressure.

microclimate factor
Factor or coefficient used to adjust reference evapotranspiration to reflect the microclimate of an area.

microirrigation: see drip irrigation

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

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

moisture sensor
Device that monitors or measures soil water content of tension.

multi-outlet dripper
Device which supplies water to two or more points through small diameter auxiliary tubing.



net irrigation
irrigation: see irrigation water requirement

non-pressure compensating dripper
Dripper designed with a fixed orifice or other components and contains no pressure compensating features.

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

number of outlets
Term used to describe the number of outlets in a lateral.

Application of plant nutrients through an irrigation system. A term that is co-registered as a trade mark by Netafim Ltd. and Haifa Chemicals Ltd. also known as fertigation



online emitter
An individual drip emitter which is connected through the walls of the polyethylene pipe to form the drip line.

organic agriculture
A holistic production management system that promotes and enhances agro-ecosystem health, including bio-diversity, biological cycles and soil biological activity. It emphasizes the use of management practices in preference to the use of off-farm inputs, taking into account that regional conditions require locally adapted systems. This is accomplished by using, wherever possible, agronomic, biological, and mechanical methods, as opposed to using synthetic materials, to fulfill any specific function within the system.



peak use rate
Maximum rate at which a crop uses water.

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 requirement. 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.

Chemical agent used to control specific organisms. Includes insecticides, herbicides, and fungicides.

Piston flow
Purely advective flow without dispersion or diffusion of the dissolved components. see plug flow

plant available water
Available water located in the root zone. same as root zone available water

plant water requirement (PWR)
see crop evapotranspiration

plug flow
plug flow: see piston flow

Flexible plastic material used to make irrigation pipe and other items.

Rate at which water, if available, would be removed from soil and plant surfaces.

potential evapotranspiration
potential evapotranspiration: see evapotranspiration

precipitation rate
Rate (in./h, mm/h) at which a sprinkler system applies water to a given area.

pressure compensating
Usually applied to drippers. Engineered to deliver a uniform flow rate even if the incoming pressure varies. Describes an emitter or sprayer that delivers a consistent amount of water over a specified range of pressures. This is useful in situations where the tubing runs are long or the terrain the tubing runs over is hilly. As a general rule, pressure compensating emitter tubing operates in the range of 10 to 50 PSI.

pressure compensating dripper
Dripper designed to discharge water at a near constant rate over a wide range of lateral line pressures.

pressure regulator
Lowers water pressure to a pre-set level that is appropriate for a drip system. Must be physically higher than any emitter placed downstream.

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-compensated emitters
Drip emitters that have a special mechanism that can maintain a uniform discharge rate in spite of great variations of water pressure.

program: see scheduling program

Acronym for pounds per square inch. see pressure



regulated deficit irrigation
RDI strategies allow a certain degree of water stress in periods when the crop is less sensitive to water deficit such as periods of lower temperatures and minimum plant growth. By applying these irrigation strategies, maximum yield can still be reached, while the amount of water applied is reduced. see deficit irrigation

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.

root depth
Depth from which roots extract water. The effective rooting depth is generally the depth from which the crop is currently capable of extracting soil water. However, it may also be expressed as the depth from which the crop can extract water when mature or the depth from which a future crop can extract soil water. Maximum effective root depth depends on the rooting capability of the plant, soil profile characteristics, and moisture levels in the soil profile

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

root zone available water
see plant available water

root zone depth
root zone depth: see root zone and root depth

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



saline soil
Soil that has sufficient soluble salts to interfere with crop growth.

saturation of soil
Condition where all soil pores/ voids are filled with 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. schedule, irrigation. see irrigation schedule

scheduling program
Set of specifications identifying times to turn on and off water to various zones of an irrigation system.

Determining timing of irrigations during the growing season and quantity of water to be applied based upon measurements or estimates of soil moisture or crop water used by a plant. Disease potential must be considered.

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

Unconsolidated minerals and material on the immediate surface of the earth that serves as a natural medium for the growth of plants.

soil electrical conductivity
The electrical conductivity (EC) of a saturated soil paste extract (ECe) is the standard soil salinity measurement used to assess plant salt tolerance. see electrical conductivity

soil fertility
Fertility of soil is its characteristics that supports abundant plant life. Fertile soil has the following properties: It is rich in nutrients necessary for basic plant nutrition, including nitrogen, phosphorus and potassium. It contains sufficient minerals (trace elements) for plant nutrition, including boron, chlorine, cobalt, copper, iron, manganese, magnesium, molybdenum, sulfur, and zinc. It contains soil organic matter that improves soil structure and soil moisture retention. Soil pH is in the range 6.0 to 6.8. Good soil structure, creating well drained soil. A range of microorganisms that support plant growth. It often contains large amounts of topsoil.

soil moisture (water) depletion
Difference between field capacity and the actual soil moisture in the root zone soil at any given time. It is the amount of water required to bring the soil in the root zone to field capacity.

soil reservoir capacity (SRC)
soil reservoir capacity(in., mm): preferred term plant available water

The space between two drippers or emitters. It depends on the type of crop and the emitter flow rates.

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.

static pressure
Water pressure when the water is at rest.

sub main
The pipeline that supplies water from the main to the laterals in an irrigation system. see branch line

Application of irrigation water below the ground surface by raising the water table to within or near the root zone.

subsurface drip irrigation
Application of water below the soil surface through drippers, with discharge rates generally in the same range as drip irrigation. The method of water application is different and is not to be confused with sub-irrigation where the root zone is irrigated by water table control.

surface irrigation
Irrigation by means of flood, furrow, or gravity. see flood irrigation, furrow irrigation, or gravity irrigation

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

sustainable agriculture
Sustainable agriculture should involve successful management of resources for agriculture to satisfy changing human needs while maintaining or enhancing quality of the environment and conserving natural resources. see alternative agriculture or bio-organic agriculture

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.



Relative proportions of the various soil separate in a soil as described by the classes of soil texture.

total water holding capacity (TWHC)
total water holding capacity (TWHC) (in., mm): preferred term is plant available water

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. see evapotranspiration

trickle irrigation
trickle irrigation: see drip irrigation

trickler: see dripper

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.



uniformity coefficient
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.

uniformity coefficient irrigation
Characteristic of the aerial distribution of water in a field as the result of irrigation.

usable precipitation
usable precipitation: see effective precipitation

uses, consumptive
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.



A device that controls flow with a system.

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



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

water application efficiency
water application efficiency: see efficiency

water holding capacity
soil moisture content in the root zone between soil moisture at field capacity and soil moisture at wilting point. also known as available soil moisture

water meter
Device used to measure to flow of water.

water pressure
water pressure: see pressure

water requirement
water requirement: see irrigation water requirement

water source
The water source is where the water comes from. This can be a municipal system, a well, a pond, an irrigation ditch, a barrel or wherever the water comes from. Usually city and well water are easy to filter for drip irrigation systems. Pond, ditch and some well water have special filtering needs. The quality of the water source will dictate the type of filter necessary for your system. Sand, silt, minerals, organic matter and rust bacteria are specific concerns.

water storage efficiency
water storage efficiency: see efficiency

water storage efficiency
Ratio of the amount of water stored in the root zone during irrigation to the amount of water needed to fill the root zone to field capacity.

water window
Time of day available for irrigation to occur.

wetted area
Surface area wetted at completion of irrigation.

wilting point (WP)
wilting point (WP): see permanent wilting point

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

working pressure
Pressure of the irrigation system during operating.



yield monitoring
Regular intervals where a harvested weight can be obtained along with a GPS reading.



Section of an irrigation system served by a single control valve. Zones are comprised of similar sprinkler types and plant material types with similar water requirements and types.