The drip irrigation system cost can be reduced effectively by using optimal design methods and decreasing the system pressure. In this paper, a two-stage optimum drip irrigation lateral design model is developed based on a new uniformity formula that includes hydraulic variation, emitter manufacture’s variation, and field roughness variation. The non-linear objective function minimizes the capital cost and the present values of the lateral operating cost. In the first stage, the pipe diameter and the emitter average pressure are taken as decision variables for the specified uniformity and lateral length. In the second stage, a commercially available pipe size that is very close to the diameter obtained in the first stage is selected. It has an allowable pressure that is a little more than or equal to 1.5 times of the maximum lateral pressure obtained in the first stage. The emitter average pressure is calculated for a known diameter. The model is applied to a case study in which the result indicates that a lateral with a larger diameter and the lower emitter average pressure can be economically justifiable. A drip irrigation system with a lower pressure should be developed on the basis of this study.
Keywords: emitter average pressure head, low pressure irrigation, trickle irrigation