OPTIMUM DESIGN AND OPERATION OF MULTIPLE SUBUNIT DRIP IRRIGATION SYSTEMS

A nonlinear model for the optimum design and operation of drip irrigat ion systems on flat terrain is presented in this paper. The analysis i s based on dividing a field into subunits and evaluating various shift patterns and the corresponding pipe and pump sizes in order to identi fy a minimum cost solution. The decision variables are the lengths of two given pipe sizes for the laterals, the diameters of all other pipe s, the size of pump, the area and dimensions of subunits, as well as t he shift patterns and the irrigation time for each shift and set of su bunits irrigated simultaneously. The optimization procedure involves a complete enumeration approach, which minimizes the sum of the capital cost of the system and the present value of operating costs. The mode l is applied to a case study of a level rectangular field supplied fro m a ground-water source at its center. The results obtained indicate t hat one shift operation is the most cost-effective provided the emitte r flow rate is above a defined minimum level.