The design of a lateral line for drip irrigation requires accurate evaluation of head losses in not only the pipe but in the emitters as well. A procedure was developed to determine localized head losses within the emitters by the formulation of a mathematical model that accounts for the obstruction caused by the insertion point. These localized losses can be significant when compared with the total head losses within the system due to the large number of emitters typically installed along the lateral line. An experiment was carried out by altering flow characteristics to create Reynolds numbers (R) from 7,480 to 32,597 to provide turbulent flow and a maximum velocity of 2.0 m s-1. The geometry of the emitter was determined by an optical projector and sensor. An equation was formulated to facilitate the localized head loss calculation using the geometric characteristics of the emitter (emitter length, obstruction ratio, and contraction coefficient). The mathematical model was tested using laboratory measurements on four emitters. The local head loss was accurately estimated for the Uniram (difference of +13.6%) and Drip Net (difference of +7.7%) emitters, while appreciable deviations were found for the Twin Plus (-21.8%) and Tiran (+50%) emitters. The head loss estimated by the model was sensitive to the variations in the obstruction area of the emitter. However, the variations in the local head loss did not result in significant variations in the maximum length of the lateral lines. In general, for all the analyzed emitters, a 50% increase in the local head loss for the emitters resulted in less than an 8% reduction in the maximum lateral length.

Document Type


Publication Date


Notes/Citation Information

Published in Transactions of the ASABE, v. 52, issue 3, p. 729-738.

© 2009 American Society of Agricultural and Biological Engineers

The copyright holder has granted the permission for posting the article here.

Digital Object Identifier (DOI)


Funding Information

These authors are grateful to the following Brazilian Institutions for their financial support: Federal Department of Science and Technology (MCT), National Scientific and Technological Development Council (CNPq), São Paulo State Scientific Foundation (FAPESP), and National Institute of Science and Technology in Irrigation Engineering (INCTEI).