Design of drip irrigation system using microtubes for full emission uniformity

Clogging and emission non-uniformity have been the major obstacles in the development of drip irrigation. To obtain best emission uniformity, pressure regulators and pressure- compensating emitters have been in use for a long time. However, pressure-compensating emitters tend to be more complex and costly than non-compensating emitters. Microtubes as small-bore polyethylene tubes can be pierced along laterals to provide simpler passages and thus less susceptibility to clogging. This paper suggests the possibility of utilizing microtubes with varying lengths to deliver equal discharges throughout a network by adjusting its pressure heads. A model based on a stepwise technique is developed considering the head losses and flow regime changes through the system. The model was run for 12 possible scenarios, under two terrains of 0 and +0.25% slopes (upward), with three (2, 3 and 4 mm) and two (12 and 16 mm) microtube and lateral diameters, respectively. Mathematical relationships and design tables and graphs are developed to design a drip network manually. To simplify the design, the concept of non-dimensional length ratios is introduced to compute the variation of microtube length difference ratios along the laterals. The microtube length difference ratios follow the same trend for all the microtube and lateral sizes chosen; hence manual computation of variable microtube lengths could be carried out by using this new methodology.