Robust bi-objective macroscopic municipal water supply network redesign and rehabilitation

Water companies traditionally deal with the problem of rehabilitation and redesign of municipal water supply system due to the either of aging the existed water supply network and housing development. However, such problems are hemmed in by uncertainty due to their long planning horizons and the fact that the exact prediction of future is impossible. Uncertain data and parameters which are likely to undermine the effectiveness of our decisions in this area, are exacerbated if they are be correlated. Unfortunately, correlated uncertain parameters are the things typically such problems are entangled with. Thus, along with considering all of decision objectives, it is incumbent upon water supply system redesign and rehabilitation decision model to develop methods able to appropriately confront with the correlated uncertainty. This paper introduces a bi-objective robust optimization model capable of handling correlated uncertain parameters in municipal water supply system redesign and rehabilitation problem. This robust optimization framework is able to adjust the level of conservatism, a factor which contributes to the reliability of the system. The proposed mathematical framework is applied for a water supply system inspired from Tehran potable water supply system and then various levels of conservatism and reliability are compared. Numerical results show neglecting uncertainty can lead to significant increase in the total cost and amount of unsatisfied demand.