Abstract:
In this study, a non linear model for the optimal design of drip irrigation system is developed for both flat and uniform slope fields. The objective function is to minimize the cost which is the sum of capital and, operating cost and, the design variables are diameter of main, submain, manifold and lateral lines, size and number of emitters, dimension of subunit. irrigation interval, application time, and number of shifts per day. To solve the model a computer code in C++ was written. The program was designed as a two stage optimization processes. In the first stage, identification of all the possible combinations of emitter discharge and number of emitters per tree based on the irrigation, requirement and available time for irrigation per day was found out. In the second stage, for each possible combination the field was divided into subunits, then subunit pipe (manifold and lateral in this case) diameters as a function of emission uniformity (EU) and, main and submain diameters based on cost were decided to determine subunit dimension with minimum cost. Further, to test the capability, of the model two sets of published data, the first with flat topography and the second with uniform slope topography were used. The model identified 11 and 3 combinations of emitter discharge and number of emitters per tree for the first and second cases respectively. Optimum costs which are equal to $216937 with subunit dimension of 200mx75m (4 1ph emitter discharge and 2 numbers of emitters per tree) and $31413 with subunit dimension of 75mx 150m (2 ]ph and I emitter per tree) were found out for the first and second data sets respectively.
