Design of paired laterals on uniformly sloping fields

Abstract

Knowledge of the maximum length for paired drip laterals facilitates the economic optimization of micro-irrigation systems. The methodologies proposed to date have been based on complicated mathematical procedures that make certain restrictive assumptions, such as fixed pressure head variation, and disregard emitter flow variation; this has limited their application. The methodology presented in this study, which assumes the basic equations for the analysis of a drip lateral based on the energy gradient line, allows evaluating the maximum length of paired drip laterals with non-pressure compensating emitters, when diameter and slope are known and pipe is laid on a uniformly sloping field. The results show that the maximum length of a paired drip lateral with given diameter is almost constant for any slope, although there is a maximum slope above which the lateral pipe diameter needs to be reduced. The maximum slope can be obtained when the ratio between the difference in elevation and the head loss due to friction of the downhill lateral exceeds one. A method is also proposed to determine the lateral pipe diameter for a fixed length.