|
Glossary
Dean E. Eisenhauer, Derrel L. Martin, Derek M. Heeren, Glenn J. Hoffman
Pages 339-347 (doi: 10.13031/ISM.2021.g) in Irrigation Systems Management. ,
Abstract. See https://www.asabe.org/ISM for a PDF file of this entire textbook at no cost.
Excerpted with permission from ASABE Standards. ASAE S526.4 SEP2015(R2019). Soil and water terminology. American Society of Agricultural and Biological Engineers: St. Joseph, Mich. https://elibrary.asabe.org/toc.asp.
- sprinkler irrigation systems:
- center pivot: An automated irrigation system consisting of a sprinkler line rotating about a pivot point and supported by a number of self-propelled towers. The water is supplied at the pivot point and flows outward through the line supplying the individual outlets.
- lateral move: An automated irrigation machine consisting of a sprinkler line supported by a number of self-propelled towers. The entire unit moves in a generally straight path and irrigates a basically rectangular area. Sometimes called a “linear move.”
- permanent: Underground piping with risers and sprinklers.
- portable (hand move): Sprinkler system which is moved by uncoupling and picking up the pipes manually, requiring no special tools.
- side-roll sprinkler: The supply pipe is usually mounted on wheels with the pipe as the axle and where the system is moved across the field by rotating the pipeline by engine power.
- solid set: System which covers the complete field with pipes and sprinklers in such a manner that all the field can be irrigated without moving any of the system.
- towed sprinkler: System where lateral lines are mounted on wheels, sleds, or skids, and are pulled or towed in a direction approximately parallel to the lateral.
allowable depletion: That part of soil water stored in the plant root zone managed for use by plants, usually expressed as equivalent depth of water in mm (acre-inches per acre, or inches).
application efficiency (Ea): The ratio of the average depth of irrigation water infiltrated and stored in the root zone to the average depth of irrigation water applied, expressed as a percentage. Also referred to as AE.
application efficiency of low quarter: The ratio of the average depth of irrigation water infiltrated and stored in the root zone as determined from the lowest 25% of the area, to the average depth of irrigation water applied, expressed as a percent.
application rate: Rate that water is applied to a given area. Usually expressed in units of depth per time.
aquifer: A geologic formation that holds and yields useable amounts of water. Aquifers can be classified as confined or unconfined.
available water capacity, AWC: The portion of soil water that can be readily absorbed by plant roots of most crops, expressed in mm water per mm soil (inches per inch, inches per foot, or total inches) for a specific soil depth. It is the amount of water stored in the soil between field capacity (FC) and permanent wilting point (WP). It is typically adjusted for salinity (electrical conductivity) and rock fragment content. Also called available water holding capacity (AWHC), or available soil water.
backflow prevention device: Safety device which prevents the flow of water from the water distribution system back to the water source.
backpressure: 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.
backsiphonage: Reversal of flow (backflow) due to a reduction in system pressure which causes a negative or subatmospheric pressure to exist at a site in the water system.
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 downfield slope are referred to as level border systems. Border systems constructed on terraced lands are commonly referred to as benched borders.
centrifugal pump: Pump consisting of rotating vanes (impeller) enclosed in a housing and used to impart energy to a fluid through centrifugal force.
Christiansen’s uniformity coefficient: A 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.
consumptive use: The total amount of water taken up by vegetation for transpiration or building of plant tissue, plus the evaporation of soil moisture, snow, and intercepted precipitation associated with vegetal growth.
conveyance efficiency (Ec): The ratio of the water delivered to the total water supplied to an open channel or pipeline at the upstream end, expressed as a percentage.
crop coefficient (Kc): The ratio of the actual crop evapotranspiration to reference evapotranspiration.
cumulative intake: The depth of water infiltrated into the soil from the time of initial water application to the specified elapsed time.
deep percolation: Water that moves downward through the soil profile below the root zone and cannot be used by plants.
discharge: Volume flux or flow rate of water, measured in units of volume per unit time. Discharge can be used to describe water flow in pipes, streams or groundwater.
distribution uniformity of low quarter: The ratio of the average of the lowest one-fourth of measurements of irrigation water infiltrated to the average depth of irrigation water infiltrated, expressed as a percent.
doctrine of appropriation: Water law developed in the arid Western states, where water supplies are limited and often inadequate (also known as the Appropriation Doctrine). This doctrine is essentially a rule of capture (first in time of use is first in right), where application of the water to a beneficial use is the basis and measure of the right.
drawdown: Lowering of the water surface, water table, or piezometric surface resulting from the withdrawal of water from a well or drain or principal spillway; also the elevation of the static water level in a well minus the elevation of the pumping water level (at the well) at a given discharge rate.
drip irrigation: A method of microirrigation wherein water is applied to the soil surface as drops or small streams through emitters. Discharge rates are generally less than 8 L/h (2 gal/h) for single-outlet emitters and 12 L/h (3 gal/h) per meter for line-source emitters.
effective precipitation: That portion of total precipitation which becomes available for plant growth.
electrical conductivity (EC): A measure of the ability of the water to transfer an electrical charge. Used as an indicator for the estimation of salt concentration, measured in dS/m (mmhos/cm), at 25 °C (77 °F).
emission uniformity: An index of the uniformity of emitter discharge rates throughout a microirrigation system. Takes account of both variations in emitters and variations in the pressure under which they operate.
emitter: A small microirrigation 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.”
evapotranspiration: The combination of water transpired from vegetation and evaporated from the soil, water and plant surfaces.
exchangeable sodium percentage (ESP): The fraction of the cation exchange capacity of a soil occupied by sodium ions determined as: exchangeable sodium (meq/100 gram soil) divided by CEC (meq/100 gram soil) times 100. It is unreliable in soil containing soluble sodium silicate minerals or large amounts of sodium chloride.
field capacity: Amount of water remaining in a soil when the downward water flow due to gravity becomes negligible. An estimate of field capacity ranges between soil water contents at matric potentials of –10 to –33 kPA (–0.1 to –0.33 bar).
flow meter: An instrument used to measure the volume and/or rate of flow of water in a conduit or channel.
flume: A specially calibrated structure for measuring open channel flows.
friction head: Energy required to overcome friction caused by fluid movement relative to the boundaries of a conduit or containing medium.
furrow irrigation: Method of surface irrigation where the water is supplied to small ditches or furrows for guiding across the field.
gross irrigation: Total water applied to a given area that may or may not equal total irrigation water requirement.
groundwater: Water occurring in the zone of saturation in an aquifer or soil.
head: The energy in the liquid system expressed as the equivalent height of a water column above a given datum.
hydraulic conductivity: The ability of a porous medium to transmit a specific fluid under a unit hydraulic gradient; a function of both the characteristics of the medium and the properties of the fluid being transmitted. Usually a laboratory measurement corrected to a standard temperature and expressed in units of length/time. Although the term hydraulic conductivity is sometimes used interchangeably with the term permeability, the user should be aware of differences.
infiltration: The downward entry of water through the soil surface into the soil.
intake family: A grouping of intake characteristics into families based on field infiltrometer tests on many soils, developed by the SCS (now the Natural Resources Conservation Service). Used to analyze and design border and furrow irrigation systems.
interlock injection device: Safety equipment used to ensure that a chemical injection pump will stop if the irrigation pumping plant stops to prevent the entire chemical mixture from emptying from the supply tank into the irrigation pipeline. An injection device may include check valves to prevent water from flowing back through the injection pump and overflowing.
irrigation efficiency: The ratio of the average depth of irrigation water that is beneficially used to the average depth of irrigation water applied, expressed as a percent. Beneficial uses include satisfying the soil water deficit and any leaching requirement to remove salts from the root zone.
lateral: Secondary or side channel, ditch, or conduit. Also called “branch drain” or “spur.” Also, water delivery pipeline that supplies irrigation water from the main line to sprinklers or emitters.
leaching: Removal of soluble material from soil or other permeable material by the passage of water through it.
manifold: Pipeline that supplies water to the laterals.
manufacturer’s coefficient of variation: A measure of the variability of discharge of a random sample of a given make, model, and size of microirrigation 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.
net irrigation: The actual amount of applied irrigation water stored in the soil for plant use or moved through the soil for leaching salts. Also includes water applied for crop quality and temperature modification; i.e., frost control, cooling plant foliage and fruit. Application losses, such as evaporation, runoff and deep percolation are not included. Generally measured in mm (inches) of water depth applied.
opportunity time: The time that water inundates the soil surface with opportunity to infiltrate.
Penman-Monteith Method: A method used to estimate reference crop evapotranspiration (ETo) using current climatic data including air temperature, relative humidity, wind speed, and solar radiation. Also referred to as the FAO Penman-Monteith Method.
permanent wilting point: Soil water content below which plants cannot readily obtain water and permanently wilt. Sometimes called “permanent wilting percentage” or WP. Often estimated as the water content corresponding to a matric potential of –1.5 MPa (–15 bar).
pump efficiency: Ratio of the water power produced by the pump, to the power delivered to the pump by the power unit.
reasonable-use rule: A concept of water law in which a landowner is given the right to the reasonable use of water for domestic or similar needs.
reference evapotranspiration: The evapotranspiration from a dense, well-watered hypothetical crop with specified height, albedo, and surface resistance. The ASCE Standardized Reference Evapotranspiration Equation recognizes two reference surfaces: short crop reference ET (ETo), which represents a clipped, cool-season grass (this is equivalent to FAO 56 reference ET), and a tall crop reference (ETr), which represents alfalfa. Reference ET is a measure of the atmospheric demand for water and is used in conjunction with a crop coefficient to estimate crop ET.
return flow: That portion of the water diverted from a stream which finds its way back to the stream channel, either as surface or subsurface flow.
riparian doctrine: This doctrine is in effect in most eastern States, some mid-western and southern States, and the State of California (which also uses the appropriation doctrine). In almost all jurisdictions, the doctrine has been modified to fit local conditions. It applies to all bodies of water including streams, lakes, ponds, and marshes, and grants to all riparian owners the right to make reasonable use of the water so long as the water use does not interfere with the reasonable use of water by other riparian users.
saline soil: Nonsodic soil containing soluble salts in such quantities that they interfere with the growth of most crops. The electrical conductivity of the saturation extract is greater than 4 dS/m (0.01 mho/in.), and the exchangeable-sodium-percentage is less than 15.
saturation: To fill all (100%) voids between soil particles with water.
sodic soil: A nonsaline soil containing sufficient exchangeable sodium to adversely affect crop production and soil structure. The exchangeable sodium- percentage is greater than 15 and the electrical conductivity of the saturation extract is less than 4 dS/m (0.01 mho/in.).
soil-water deficit: Amount of water required to raise the soil-water content of the crop root zone to field capacity. It is measured in mm (inches) of water. Also called soil-water depletion.
soil-water tension: A measure of the tenacity with which water is retained in the soil. It is the force per unit area that must be exerted to remove water from the soil and is usually measured in bars, or atmospheres. It is a measure of the effort required by plant roots to extract water from the soil.
solar radiation (Rs): Radiation from the sun that passes through the atmosphere and reaches the combined crop and soil surface. The energy is generally in a waveband width of 0.1 to 5 microns. Net Rs is incoming minus reflected radiation from a surface.
specific capacity: Well discharge divided by the water level drawdown after a specified pumping duration.
sprinkler head: A device for distributing water under pressure.
subsurface drip irrigation: Application of water below the soil surface through emitters, with discharge rates generally in the same range as drip irrigation. This method of water application is different from and not to be confused with subirrigation where the root zone is irrigated by water table control.
water table: The upper surface of a saturated zone below the soil surface where the water is at atmospheric pressure.
weir: Any of a group of flow measuring devices for open-channel flow. Weirs can be either sharp-crested or broad-crested. Flow opening may be rectangular, triangular, trapezoidal (Cipolletti) or specially shaped, e.g., to make the discharge linear with flow depth (sutro weir).
well casing: Pipe installed within a borehole to prevent collapse of sidewall material, to receive and protect pump and pump column, and to allow water flow from the aquifer to pump intake.
well screen: That part of the well casing which has openings through which water enters.