Variation of design parameters in micro-irrigation laterals

Abstract

Micro-irrigation laterals deliver irrigation water to the plant root zones through emitters in a micro-irrigation (drip, trickle) system. Adequate analysis of micro-irrigation laterals is very important for the design and evaluation of micro-irrigation systems. Design of a lateral pipe includes the determination of the pipe length or the inside diameter, the required operating inlet pressure head and total friction head losses along the lateral assuming that the total flow rate at the inlet, characteristic of the emitter, and the acceptable level of uniformity are known previously. In this study, the forward-step method (FSM) that takes into account to the velocity head change and variation of the Reynolds number, which affects the selection of the proper friction coefficient formula to be applied along the different reaches of the lateral pipes was presented, and then, a computer program in Visual Basic 6.0 language named LATCAD was provided for analyzing and designing of micro-irrigation laterals. This method has the highest accuracy because only the basic equations of the hydraulics of steady pipe flow were used. In this study, variation of the operating inlet pressure head, total friction head losses and uniformity coefficients depend on the pipe lengths ranging between 25 and 250 m and the internal diameters ranging between 10 and 21 mm in zero slope condition were evaluated graphically in dimensionless form for practical purposes. These presented figures could also be used as the design charts. The results of computer program based on the forward-step method are in close agreement to those obtained by other researchers.