ANALYSIS AND DESIGN OF TRICKLE-IRRIGATION LATERALS

The problem of a lateral pipe with equally spaced emitters and uniform slope is investigated. Individual emitters are considered in discharge and pressure estimations along the lateral. The friction head loss between successive emitters is estimated by the Darcy-Weisbach formula, taking into account the variation of the Reynolds number, the different zones on Moody diagram, and the friction coefficient formula corresponding to each zone. In addition, the change of the velocity head is accounted for at different emitters. As the net pressure head at each emitter is evaluated, the corresponding emitter discharge is estimated accordingly. A computer program is presented for analyzing and designing trickle-irrigation laterals. The results of two numerical examples solved using the presented technique are in close agreement with those of other rational analysis. Laminar flow prevails in a considerable length at the downstream end of the lateral, whereas an upstream length may be subject to fully turbulent flow. The estimation of the lower-quarter distribution uniformity shows that considering individual emitters rather than longitudinal slot is of practical importance. Design criteria for trickle-irrigation laterals are provided.