This paper presents a simulated annealing multiobjective algorithm developed to include novel features for promoting the convergence toward the best Pareto front that shows diversity and uniformity in the distribution of solutions. The new algorithm, MultiObjective Simulated Annealing with new Generation and Reannealing procedures (MOSA‐GR), is a trajectory‐based algorithm, where, in a first phase, diversified generation strategies are used to define candidate solutions at different stages of the search procedure. In a second phase a reannealing process starting at low temperature is implemented to intensify the search based on the last solutions of the first phase. An extensive comparison with solutions obtained by various multiobjective evolutionary algorithms (MOEAs) described in the literature is provided. Using a limited budget for the number of function evaluations, the results show that MOSA‐GR has a very good performance and gives rise to better fronts, even compared with those obtained by merging the results from different MOEAs implemented in similar conditions.

In the face of a highly uncertain future, there is a need for water utilities to develop structured approaches for the long-term strategic design of water distribution networks (WDNs). A new conceptual framework for developing an integrative approach based on a multicriteria decision analysis (MCDA), embracing an optimization model to size flexible alternatives, is proposed. The flexible solutions are evaluated through MCDA for all the criteria (investment costs, carbon emissions, resilience, and reliability of WDNs) across all the scenarios generated for the sake of robustness and will help to adapt WDNs to changing conditions over a long planning horizon, divided into phases. The alternatives are ranked through two different MCDA methods, Preference Ranking Organization METHod for Enrichment of Evaluations (PROMETHEE) and Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS), so that decision makers will have more comprehensive information for analyzing highly ranked design solutions and after the first phase, solutions for the other phases can be reassessed by the same dynamic adaptive framework.

Copyright © 2015 American Society of Civil EngineersWater supply systems have to satisfy water needs in terms of quantity and quality. The constant changes in urban areas require the regular adaptation of the water supply infrastructure to meet new circumstances. However, decisions to design and operate water networks have to be taken under uncertainty. Flexibility is thus the key to more robust and confident decisions. An approach called real options (ROs) can be used in these situations. This approach makes it possible to use adaptive strategies in the decision process. Some decisions can be delayed pending future conditions. Water distribution systems are very costly and complex infrastructures. Once built, their operating structure cannot be changed significantly. This work presents an innovative ROs approach to define an objective function to cope with some future scenarios in a specific case study. The objective of our proposed model is to find a minimum cost solution for the first period of a planning horizon, while considering various possible future conditions that the network could have to cope with. The results of this work show that building flexibility into the decision strategy makes it possible to take an adaptive approach that can avert future lack of network capacity. In the case study, an adaptive design of the network incurs an extra initial cost, but this cost can easily be lower than the cost of reinforcing the network in a longer planning horizon. The real value of ROs is their ability to adapt systems to different possible future scenarios.Fundo Europeu de Desenvolvimento Regional (FEDER) funds through the Programa Operacional Factores de Competitividade (COMPETE)Fundação para a Ciência e Tecnologia (FC