Designing Trickle Irrigation Systems in Sloping Fields without Pressure-Compensating Emitters: Application of the IRRILAB Software

Abstract

When designing trickle irrigation systems in sloped fields, the use of pressure-compensating (PC) emitters is generally preferred to ensure the emitter distribution uniformity regardless of the land topography and the variable operating pressures. However, the cost of PC emitters is generally higher than non-pressure-compensating (NPC) ones; moreover, the compensating membrane installed inside the emitters can lose elasticity due to the exposition to solar radiation, water quality, and chemical applications. Recently, the irrigation laboratory (IRRILAB) version 1.0 software application was developed to design microirrigation systems for rectangular and planar sectors when using NPC emitters under any field slope and by neglecting the local losses due to the emitter connections. The objective of this work is to demonstrate that even in sloped fields and neglecting the local losses, it is possible to use NPC emitters by maintaining acceptable values of field distribution uniformity. In addition, the influence of local losses caused by the emitters installed in the laterals is also investigated to assess their role in the examined applications. The IRRILAB software was initially used to design a microirrigation sector, to suggest the optimal operating pressure, and to simulate the operating pressure heads and flow rates. The latter values were compared with the corresponding values measured in the field. The software was additionally assessed based on a second experimental campaign, after limiting the length of the laterals to account for local losses. For both experimental campaigns, the values of the commonly used uniformity coefficients were deemed acceptable according to the American Society of Agricultural Engineering (ASAE). However, the introduction of minor losses in the hydraulic design showed an improvement in terms of the emitters’ flow rate distribution in the whole sector and uniformity coefficients.