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

Adhesion Physical attraction of unlike substances to one another.  In soils, it is the process that holds water molecules tightly to soil solids at the soil-water interfaces.

Adjusted sodium adsorption ratio Index of permeability problems, based upon water quality.

Adsorption Concentration of a substance at the surface of another, more noticeable with substances of large surface area, such as clay particles.

Advance ratio Ratio of the time for the water to reach the end of the field to the total set time for an irrigation set on a furrow irrigation system.  The ratio should be less than 0.5 to have a good distribution uniformity.

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

Aggregate Groups of individual soil particles, held together naturally and consisting of particles of sand, silt and clay separated from each other by pores, cracks or planes of weakness.  The term, soil structure, refers to this arrangement of the soil in natural aggregates. Various types of soil structure are recognized (Massive, platy, prismatic, blocky, granular).

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.

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.

Backflow 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 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.

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.

Bubbler 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.

Cablegation Method of surface irrigation that uses gated pipe to both transmit and distribute water to furrows or border strips.  A plug, moving at a controlled rate through the pipe, causes irrigation to progress along the field and causes flow rates from any one gate to decrease continuously from some maximum rate to zero.

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.

Cavitation 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.

Certified Agricultural Irrigation Specialist (CAIS) The Certified Agricultural Irrigation Specialist is involved in the management and operation of on-farm irrigation systems. These systems include surface irrigation methods, as well as pressurized systems like micro-irrigation and sprinklers. Prior to certification examination, specialists are required to take an Irrigation Association approved preparatory course.

Certified Golf Irrigation Auditor (CGIA) The Certified Golf Irrigation Auditor is involved in the analysis of turf irrigation water use tailored to the unique conditions found on golf courses. Golf Auditors collect site data, make maintenance recommendations and perform water audits on golf courses. Through their analytical work at the site, these irrigation professionals develop base schedules for greens/tees, fairways and roughs. Prior to certification examination, auditors are required to take an Irrigation Association approved preparatory course.

Certified Irrigation Contractor (CIC) The Certified Irrigation Contractor is an irrigation professional whose principle business is the execution of contracts and subcontracts to install, repair and maintain irrigation systems.  The CIC must conduct business in such a manner that projects meet the specifications and requirements of the contract.

Certified Irrigation Designer (CID) The IA Certified Irrigation Designer engages in the preparation of professional irrigation designs.  They evaluate site conditions and determine net irrigation requirements based on the needs of the project.  The designer is then responsible for the selection of the most effective irrigation equipment and design methods.  The objective of a CID is to establish specifications and design drawings for the construction of an irrigation project.

Certified Landscape Irrigation Auditor (CLIA) The Certified Landscape Irrigation Auditor is involved in the analysis of landscape irrigation water use.  Auditors collect site data, make maintenance recommendations and perform water audits.  Through their analytical work at the site, these irrigation professionals develop monthly irrigation base schedules.  Prior to certification examination, auditors are required to take an Irrigation Association approved preparatory course.

Certified Landscape Irrigation Manager (CLIM) The Certified Landscape Manager is an irrigation professional familiar with all areas of turf irrigation design and construction management. CLIMs must be certified as CICs, CID (all Landscape/Turf specialty areas), and either as a CLIA or CGIA. Certified Landscape Irrigation Managers have extensive experience in design, construction, construction management and auditing of turf irrigation systems.