Ecology, Environment and Conservation Paper

OPTIMAL DESIGN OF IRRIGATION NETWORKS USING MIXED INTEGER LINEAR PROGRAMMING

B. Shahi Nejad, H.M.V. Samani, H. Mosavi Jahromi and M. Shafaei Bajestan

Abstract

The problem of selecting the best arrangement for the pipe diameters and the optimal pumping head so as the minimal total cost to be produced, has received considerable attention many years ago by the engineers who study hydraulic works. In this study, a mixed integer linear programming (MILP) model is presented for optimization of pressurized branched irrigation networks. The objective function of the MILP consists of the equivalent annual fixed cost of pipe network of the irrigation system and its annual operating energy cost.The hydraulic constraints in the optimization problem consist of the energy conservation, nodal pressure head and pipe flow velocity constraints. The input data are the system layout, frictional head loss, costs of pipes in all the commercially available sizes, cost of pressure generating facilities such as pumps and the hydraulic upper and lower bounds constraints. The output data are: optimum diameters of the pipes, operating pressure heads, and equivalent total annual cost of the pipeline in the network. Performance of the developed mix integer linear programming model is assessed with different design problems of pressurized irrigation system already solved by other researchers. Solutions generated by the proposed model in comparison with the analytical methods, linear programming and other numerical solutions show a good performance.The proposed model has also been used for design of main and submain pipes in a real case study. Detailed analysis of the results is reported and compared with those generated based on trial-and-error method. The proposed method results in a reduction of 12.5% in costs.