Increasing convergence rate in two-objective optimization of water distribution network with engineering judgment

Background: Water distribution networks (WDNs) are facilities that require massive investment and their optimization is very important. This study aimed to optimization and development of models for promoting WDNs with using engineering judgment. In this method, instead of controlling all system states, it is possible to search the optimal set of options based on engineering judgment and hydraulic and physical status of the system. Thus, the time to solve the optimization problem is greatly reduced, which is very important in widespread networks with many components. The case study was a WDN in western Tehran. Methods: To reduce the calculation size and increase the convergence rate using engineering judgment, the parts of the network where there was no possibility of parallel piping was ignored. For other parts with a low pressure problem, parallel piping was defined. A FMGA and WaterGEMS hydraulic software were used to optimize the WDN. Cost minimization and pressure benefit maximization were the objective functions and the diameters of the pipes were considered to be the decision variables. Results: The results of optimization the network showed that, the cost decreased 89.84% and the pressure in all nodes, except one node, reached within the standard range (26-60 mH20). It included 2387 m of pipe with diameters of 100, 150, 200, 250, 350, 400 and 500 mm. Conclusion: The results of optimization and modification of the network using engineering judgment confirm that the cost decreased significantly and the pressure level in all the nodes increased to above the allowable minimum pressure.