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Irrigation Glossary <br />Page 2 of 7 <br />%,unveyance crnciency <br />The ratio of the water that is delivered to a field to the total water diverted or pumped into <br />the conveyance system at the upstream end. [%, decimal] <br />Corrugation Irrigation <br />Surface irrigation method where small channels or corrugations are used to guide water <br />across a field. No attempt is made to confine the water entirely to the corrugations. <br />Crop Coefficient <br />A number that is multiplied by the potential evapotranspiration to obtain the actual crop or <br />plant evapotranspiration. They are crop dependant numbers and change over time with the <br />crop's growth stage. [unitless] <br />Deep Percolation <br />Movement of water downward through the soil profile below the root zone. This water is lost <br />to the plants and eventually ends up in the groundwater. These water losses can be <br />significant and are often out-of-site and therefore out-of-mind. [in, mm] <br />Deficit Irrigation <br />Not completely refilling the soil profile to field capacity. Not giving the plants all of the water <br />that they can use. This may be deliberate, or inadvertent. <br />Distribution Uniformity <br />Test for determining the evenness or uniformity of irrigation water over an area. Numerical <br />indices of uniformity include DU (distribution uniformity of the low quarter) and CU <br />(Christiansen coefficient of uniformity). [unitless] <br />Drip Irrigation <br />Also known as trickle or micro-irrigation. Water is applied at very low flow rates (drip) <br />through emitters directly to the soil. Emitter flow rates are generally less than 3 gallons per <br />hour. <br />Effective Precipitation <br />Portion of the total precipitation that is stored in the soil profile for later use by the plants. [in, <br />mm] <br />Efficiency <br />See application efficiency, irrigation efficiency, conveyance efficiency, pumping plant <br />efficiency, motor efficiency, pump efficiency, or water use efficiency. [%. decimal] <br />t Emitter <br />Also known as a dripper. Used in drip irrigation to control the flow of water into the soil. <br />Evaporation <br />toss of water as vapor from the soil surface or wet leaves. Differs from transpiration in that <br />the water does not pass through the plant leaves. [in, mm] <br />Evapotranspiration (ET) <br />Combined water lost from both transpiration from plant leaves and evaporation from soil and <br />wet leaves. Also known as crop water use, or consumptive use. The crop ET (ETc) can be <br />estimated by calculating the reference ET for a particular reference crop (ETo for clipped <br />grass, and ETr for alfalfa) from weather data and multiplying this by a crop coefficient. [in, <br />mm] <br />Fertigation <br />Application of fertilizers through the irrigation system. A form of chemigation. <br />I xrttp.//in igati on. wsu. edu/glossary. php i nnoo8 <br />81