Dual-Diameter Drip Laterals Laid on Flat Fields: Modelling and Measurements

Recently, under the assumption of constant emitter flow rate, simplified procedures to design microirrigation units without using pressure compensating emitters (PC) have been suggested, and a software named IRRILAB, allowing for saving energy and not considering local losses due to the emitters insertions, was developed. The principle of IRRILAB software in saving energy is based on the rationale that the entire admitted range of pressure head variation, established by a design unit pressure head tolerance, must be used during the irrigation system operation. Moreover, it was demonstrated that if the lateral pressure head tolerance is sufficiently tight, the constant emitter flow rate assumption provides negligible errors in the pressure head distribution (PHD), compared to the numerical solution derived by the exact stepwise approach. By using the same IRRILAB approach, for laterals laid on flat fields, this paper extends the simplified solutions to dual-diameter laterals, also considering local losses that for a high number of the emitters might not be negligible. Simple relationships for the pressure head tolerances of the dual-diameter laterals and the characteristics of the emitters are presented, the latter helping to select the commercial non-pressure compensating emitters (NPC). The procedure was positively tested through numerical and experimental tests.