The handbook of Technical irrigaTion informaTion - Hunter Industries

Handbook of Technical Irrigation InformationVariables and UnitsSYMBOL DEFINITION ENGLISH UNITS SI UNITSa Cross-sectional area of pipe flow inches² mm²A r Area of land feet² acres m², haA e Area of land feet² m²AW Available soil water iches centimetersBP Barometric pressure feet metersC Hazen-Willimas friction coefficient none noneC u Christiansen’s coefficient of uniformity percent percentd Inside diameter of a pipe inches millimetersd v Difference between an observed value and the mean value inches³ mLD t Diameter of throw of sprinkler feet metersDU Distribution uniformity percent percentE Elevation of a point feet metersEA Application Efficiency percent percentET c Crop Evapotranspiration inches per day millimeters per dayET o Reference Evapotranspiration inches per day millimeters per dayH Energy head, usually sum of elevation and pressure feet metersI Electrical current amps AID Inside diameter of pipe inches meters/metersh f Energy loss due to friction feet/feet meters/metersK c Crop Coefficient percent percentkPa Kilopascals PSI barsk s Constant used to compute sprinkler spacing none noneL Spacing between lateral lines feet metersMAD Management allowed depletion none noneMC Maximum coverage for single row sprinklers feet metersn Number of observations in a uniformity test none noneNPSHA Net positive suction head available feet metersNPSHR Net positive suction head required feet metersOD Outside diameter of pipe inches millimetersP Pressure of water pounds per inch² (PSI) kPa, barsPal Allowable loss in pressure pounds per inch² (PSI) kPa, barsPav Average pressure in a zone pounds per inch² (PSI) kPa, barsPET Potential evapotranspiration inches per day millimeters per dayPSIPounds per square inchPR Precipitation rate inches per hour millimeters per hourPL Pressure losses due to friction feet metersPo Sprinkler operating pressure PSI kPa, barsPv Pressure Variation percent percentP s Static Pressure PSI kPa, barsQ Flow of water in a pipe or from a sprinkler gallons per minute liters per secondq e Flow of water gallons per minute 1/minute, m³/hrR Electrical resistance ohmsRt Radius of throw of sprinkler feet metersRAW Readily available water inches millimetersS Sprinkler spacing feet metersSC Scheduling coefficient ratio ratioSD Scalloped distance feet meterst Time of application or other timed events h hTDH Total dynamic head feet metersv Average velocity of water in a pipe feet per second (fps) meters per secondV o Electrical voltage volts VVP Vapor pressure of water feet metersXMean of all values in Cu eq.X LQMean of the lower one-fourth of the application values, Du eq.z Change in elevation between two points feet meters28