Procedures for Determining Maximum Emitter Discharge in Subsurface Drip Irrigation

One problem associated with subsurface drip irrigation (SDI) is the reduction in discharge resulting from soil-water back-pressure at the emitter outlets. An experimental setup was made to measure emitter discharge and pressure at the emitter outlet in different soils. Experiments were carried out with 2-24 L/h noncompensating and compensating emitters, operating at a constant lateral pressure of 10 m. Emitter discharge was reduced to a range of 2-10% for noncompensating models and to less than 1% for compensating models. Soil pressure ranged from 0.15-2.07 m. Laboratory conditions were simulated with HYDRUS-2D/3D. Experimental values of discharge and soil pressure showed good agreement with estimated values. Finally, maximum emitter discharge to limit the decrease of discharge was determined for an operating pressure of 10 m. For a 10% decrease, considering a constant radius of the spherical cavity in the soil, maximum emitter discharge was 2: 35 L/h for loamy soil and 12: 44 L/h for sandy soil for noncompensating emitters, and 10.73 and 54: 51 L/h, respectively for compensating emitters. These values increased when considering a cavity radius variable with emitter discharge. DOI: 10.1061/(ASCE)IR.19434774.0000299. (C) 2011 American Society of Civil Engineers.