Determining hydraulic characteristics in laterals and drip irrigation systems

Evaluation methods for functioning drip irrigation units are proposed to determine the hydraulic characteristics of emitters and pipelines. The aim of the study was to characterize the discharge curve of the emitters, their coefficient of variation, and the head losses in laterals and submains. In the laboratory, four laterals were tested under a wider range of pressure heads than the typical values of field installations. In additional, a field irrigation unit was evaluated. The discharge curve and coefficient of variation were determined in the unit with an accuracy similar to that obtained from laboratory experiments. For self-compensating emitters, a constant flow rate above the lower limit of the compensating range and an orifice-type discharge curve below that limit are proposed. For non-compensating emitters, an orifice-type discharge curve, with exponent x = 0.5, except for specific cases, is proposed. The manufacturing coefficient of variation was independent of pressure and relatively low for all the analysed emitters. Regarding the parameters of the local head losses, the equivalent length le presented values more independent of the flow than coefficient K. For the characterisation of laterals with self-compensating emitters, it is recommended to measure with the downstream end open to reduce the uncertainty in the experiments. The results show that the unit can be operated so that the average discharged flow and the uniformity can be matched just controlling the pressure head at upstream end point of the unit.