Key issues and challenges for &#160;managing water distribution networks under uncertainty&#160;
Authors: Cunha Maria C. 
Published: March 2024

Water distribution networks (WDNs) are essential systems that supply water for the most basic normal activities of our society. Their design is a complex problem because WDNs must function properly, permanently responding to consumer needs and taking into account many different technical and social issues.In recent decades, they have been extensively studied considering only a single demand setting. Therefore, the pipe sizes obtained using this approach are unreliable to address a wide spectrum of situations that WDNs face during their service life. Water demand is one of the most important sources of uncertainty for the design of WDNs.In fact, water demand is affected by different types of uncertainty (Walker et al., 2003). It can be the result of users' behavioural variability on a daily and seasonal scale (which can be classified as 'statistical uncertainty&#8217;) and can also be related to "social variability" due to the unpredictable nature of social, economic, and cultural dynamics (a more challenging level of uncertainty, 'scenario uncertainty').&#160; 'Statistical uncertainty&#8217; can be addressed by extracting information from available data and making assumptions about the statistical parameters of water demand distribution (Magini et al., 2019). 'Scenario uncertainty&#8217; may be handled through various approaches for creating plausible future demand changes i.e., likely assumptions about the future hypotheses on demand change that can concern the number of users, socio-economic situation, changes in technology, tariffs, cultural dynamics and users' behaviour (Cunha. 2023).Robust optimization models may embrace scenarios with different levels of demand uncertainty. It is essential to generate demand scenarios to develop robust WDNs, in multi-objective environments, including issues such as their reliability and the level of service they provide (Cunha et al., 2023). Thorough comparisons of the robustness of WDNs sized either using deterministic approaches or considering different levels of uncertainty are vital to understand the benefits of these last ones.This presentation will provide an overview of the key issues and challenges in defining robust WDNs to cope with multiple states of the world.&#160;REFERENCESCunha, M. C. (2023). Water and Environmental Systems Management Under Uncertainty: From Scenario Construction to Robust Solutions and Adaptation. Water Resources Management, 1&#8211;15Cunha, M. C., Magini, R., &amp; Marques, J. (2023).&#160; Multi-objective optimization models for the design of water distribution networks by exploring scenario-based approaches. Water Resources Research, 59, e2023WR034867. https://doi. org/10.1029/2023WR034867Magini, R., Boniforti, M. A., &amp; Guercio, R. (2019). Generating scenarios of cross-correlated demands for modelling water distribution networks. Water (Switzerland), 11(3), 493.Walker, W. E., Harremo&#235;s, P., Rotmans, J., van der Sluijs, J. P., van Asselt, M. B. A., Janssen, P., &amp; Krayer von Krauss, M. P. (2003). Defining Uncertainty: A Conceptual Basis for Uncertainty Management in Model-Based Decision Support. Integrated Assessment, 4(1), 5&#8211;17.Acknowledgments: The author thanks the Portuguese public agency &#8220;Funda&#231;&#227;o para a Ci&#234;ncia e a Tecnologia&#8221; (FCT) the support of national funds under the project UIDB/ 00285/2020.&#160;