Abstract:
Clogging and emission non-uniformity have been the major obstacles in the development of drip
irrigation. To obtain best emission uniformity (EU) the pressure regulators and pressure
compensating emitters are in use since long back. As pressure compensating emitters tend to be more
complex, we suggest the possibility of utilizing varying length small bore polyethylene tubes (2-4
mm) along the laterals to provide simpler passages. The lengths of these small bore microtubes are
varied according to the varying heads along a lateral that required to be compensated to deliver equal
discharges. As such, the computed set of varying length microtubes that are emitting equal flows at
the end-lateral can be replicated (i.e., by taking the same set of lengths) to subsequent laterals of the
manifold to function them as larger emitters to have similar characteristic head-discharge
relationship. As because the same set of microtube lengths are replicated to other laterals at upstream
increasing heads, the variation of flows through those laterals are restricted by limiting their number
to have EU ≥ 90 percent threshold. For case studies with EU ≥ 90 percent threshold on flat-ground
for a given set of microtube (2-4 mm) and lateral (10-14 mm) diameters, the exponents in the headdischarge
relationship varied narrowly: 0.60-0.69 for larger discharges and 0.78-0.84 for smaller
discharges. Variation of the corresponding microtube lengths can be around 0-85% longer than the
given minimum length ( min =1.25 m). When the required discharges and diameters of microtube,
lateral and manifold and some other ground conditions are given, the length of the microtubes, the
heads, emission uniformity and the best subunit dimensions can be obtained using the algorithm
developed.
