Compatibility Assessment of Drip Irrigation Laterals

Abstract

Emitters inserted in drip irrigation laterals cause local head loss, generally estimated as a product of a coefficient and the velocity head. This local head loss coefficient and the emitter discharge curve hydraulic parameters may exhibit considerable variability attributable to the manufacturing process. This paper provides a framework for assessing whether the variability in the hydraulic parameters could lead to significant differences in the performance of rolls of drip irrigation laterals from the same manufacturing batch. A system approach with inlet pressure as input, pressure distribution along the drip lateral and inlet discharge as outputs (or responses), and a drip lateral hydraulic model as the transfer function is explored. Within a Bayesian statistical framework of parameter uncertainty based on the Metropolis algorithm, the hydraulic parameters of pressure-compensating drip lateral rolls from the same manufacturing batch were inferred (calibrated). Overlapping of the space (region) of the hydraulic parameters of different drip laterals give an indication of compatibility (similarity) of the drip laterals. Results indicated that half of the drip lateral rolls tested were strongly compatible, a third were weakly compatible, and the remainder were not compatible with any other. This finding has significant ramifications in the design of drip irrigation lateral networks. Therefore, it is essential to closely examine the hydraulic properties of drip laterals for the design of drip irrigation networks to avoid poor performance of the system.