Reliability surrogate measures for water distribution system design: Comparative analysis

Because of the large computational burden associated with the direct assessment of reliability, the indirect indices of reliability have recently received more attention in the framework of water distribution system design. Two new energy-related indices for reliability evaluation (i.e., available power index and pipe hydraulic resilience index) are developed in this paper. The performance of these new indices is evaluated and compared with that of four existing indices (three other energy-related indices—i.e., resilience index, network resilience index, and modified resilience index—and the entropy-based method, i.e., diameter-sensitive flow entropy) according to the following two-step methodology. In the first step, the application of the multiobjective optimization makes it possible to determine optimal network configurations that trade-off the installation cost (to be minimized) against the generic indirect reliability index (to be maximized). In the second step, the performance of the optimal solutions in terms of explicit reliability assessment is examined under conditions in which the original network is perturbed by applying demand variations and random pipe failures to account for future operating uncertainties. The Hanoi and the Fossolo benchmark networks are used as case studies. The results obtained show that energy-based indices yield an overall superior estimate of reliability in comparison with the diameter-sensitive flow entropy. Furthermore, the new indices show some advantages in the evaluations performed under demand and pipe failure uncertainties.