Design of drip irrigation system using microtubes

To obtain the best emission uniformity in drip irrigation the pressure regulators and pressure compensating emitters are in use since long back. In contrast, clogging has been the major obstacle, particularly in areas with brackish water where problems of precipitation of calciumcarbonate, organic materials and suspended sands are severe. Microtubes as small bore polyethylene tubes of approximately 2.0-4.0 mm internal diameters can be used to deliver equal discharges, by varying its length to adjust varying heads along a given lateral. These microtubes can be simpler than inside passages of those traditional drippers and thus will be less susceptible to clogging. The computed set of varying length microtubes that are emitting equal flows at the end-lateral can be copied to subsequent laterals of the manifold to work them as larger emitters with a characteristic pressure-discharge relationship. As such the variation of flow through these laterals is restricted by limiting their number to have emission uniformity EU >= 90%. For case studies on flat-ground for a given set of lateral diameters (10-16 mm), the exponents in the pressure-discharge relationship varied narrowly: 0.60-0.69 for larger discharges and 0.78-0.84 for smaller discharges. Similarly on sloping terrain at S = 0.25% and 0.5%, the exponents varied relatively widely: 0.62-0.92 and 0.84-0.95 for larger and smaller discharges, and 0.65-0.97 and 0.85-0.99 for larger and smaller discharges, respectively. It can be reasoned that these laterals function as long path emitters. Variation of the corresponding microtube lengths can be around 0-85%, 0-460% and 0-810% longer than the given minimum length (l(min) = 1.25 m), respectively. When the required discharges and diameters of microtube, lateral and manifold and other ground conditions are given, the length of the microtubes, the pressure heads, emission uniformity and the best subunit dimensions can be obtained using the algorithm developed in this research.