Resilience and risk management in urban water supply: assessing the potential contribution of alternative systems

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Background The global urban water sector faces colossal challenges in meeting growing demands from depleted resources. While climate change and urbanization gradually exacerbate these challenges, the frequency of disruptive events such as natural and man-made disasters also rises. Investment is urgently required in Canadian cities to upgrade aging water infrastructure, while recent events in Southern Quebec highlighted the vulnerability of inflexible water systems to shocks. Diversifying sources and infrastructure is put forth as a strategy to increase resilience of urban water systems (UWSs), namely through decentralized alternative water systems (AWSs) based on wastewater or rain/stormwater. With a legacy of centralized infrastructure, integration of AWSs results in the co-existence of centralized and decentralized systems. Such hybrid systems create increased interconnections, which are poorly understood: models are needed to examine the impact of AWSs on centralized systems and on UWSs' resilience. Objective and approach This program will generate cutting-edge science and analytical approaches incorporating state-of-the-art quantitative risk assessment methods and modeling in support of improved risk management and resilience in urban water supply under natural and anthropogenic pressures and shocks. Through HQP training (3 PhDs and 4 MScAs), models will be developed to simulate hybrid systems and compare the resilience of the UWS from source to tap under different risk scenarios. The Greater Montreal Area (GMA) is used as a study region harboring several municipalities concerned with water supply resiliency; yet this study explores the theoretical implications of the models and findings at a global scale. Two dimensions of the water supply risk are considered: (i) water quantity, the risk of a water shortage (WS) and (ii) water quality, the public health risk (PH) from exposure to inadequate water quality. Quantitative Microbial Risk Assessment will be used to evaluate the probability of infection derived from reference pathogens/indicators in drinking or alternative water. Monte Carlo simulations will be used to calculate WS and PH risks under different pressure scenarios on centralized vs. hybrid UWSs. Impact This program is unifying in terms of working across disciplines at the city scale through expert collaborations. It provides (i) a much needed hybrid model, critical to understanding the impact of AWSs on water supply resilience under different risk scenarios, (ii) tools and guidance on proactive adaptation, short/medium and long-term shock responses and communication support to decision makers. Models and results are tailored to the needs of the GMA but can be adapted to other cities and contribute to the broader fields of climate and disaster resilience with foreseen applications in other sectors involving critical infrastructure.