An analytical method is presented to design multiple outlet pipes under fairly constant outflow using the energy drop ratio approach. Five pressure-head grade-line profiles were evaluated. The maximum length of the irrigation pipe that complies with Christiansen criterion was developed for level, upslope, and downslope pipes, respectively. The main advantage of this approach is that it provides the tools whereby a designer can make the tradeoff between inlet pressure head, emitter flow variation, pipe length, pipe diameter, and slope. For downsloped pipes, analytical criteria are derived to adjust the slope to the pipe diameter (or vice versa) for a given set of input data. Likewise, limits of the slope ensuring the existence of one or two abscissas for the mean pressure head are explicitly defined. Illustrative examples display a fair correlation between results generated by the present method and those provided by the stepwise approach.
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