Metabolism-based Modelling for Sustainability Assessment of Urban Water System: A Case Study of Reggio Emilia, Italy

Water resources in urban areas have been managed for a long time following the engineering approach, that increases consumption of resources (water, energy, chemicals, etc.) when a larger amount thereof is required by the users. In this approach, little attention has been paid to the pressure exerted in the long term on the environment and on the effective availability of such resources. Recently, the sustainability paradigm is gaining credibility also because of the additional “water stress” deriving from global warming. TRUST (TRansitions to the Urban Water Services of Tomorrow) is an EU integrated research project aimed to massively use the sustainability paradigm for the planning and management of urban water cycle services (UWCS). To manage sustainability in urban areas, TRUST extends the original definition of the Triple Bottom Line (WCED, 1987) upon including two additional domains, needed to take into account the assets and the governance characterizing the UWCS. In the TRUST perspective, the main goal to be achieved at the strategic horizon is being more sustainable than now. Therefore, all efforts (structural and non-structural) have to be aimed to this purpose. To support water companies to this objective, TRUST is developing methodologies and tools able to provide sustainability performances estimates and to support the selection, among a given panel, of the most suitable interventions (i.e. infrastructures, procedures and best practices) to be undertaken. The holistic approach followed in TRUST can be summarized as: a) assessment of the current sustainability level; b) setting of the sustainability target at the strategic horizon; c) definition of a set of suitable interventions to match the targets in agreement with stakeholders expectations; d) use of the available tools (e.g. metabolism model, risk manager, decision support, etc.) to find the best combination of interventions (roadmap); e) implementation of the roadmap; f) evaluation of sustainability results at intermediate time horizons; g) fine-tuning the interventions to be done; h) adjusting of the sustainability targets and i) selection of additional interventions if needed. TRUST tools are based the innovative use of the “metabolism model” and are assembled in a novel DSS, which allows the selection of the eligible interventions from the panel of the available technologies and procedures tested by the water companies in field applications during the project. All the developed tools originate from the real needs of the water company involved in TRUST, organized in City Clusters sharing similar pressures and climatic conditions. The effectiveness of the interventions is measured by the enhancements of the whole system in terms of sustainability. Furthermore, the quantitative analysis is complemented by a risk manager, aimed to provide a clear picture of the risk of not being sustainable (not matching the sustainability target) due to unmanaged or underestimated effects of the pressures acting on the system or to the ineffectiveness of the implemented barriers. A successful application of the TRUST methodology requires a close collaboration between water companies, regulators, and stakeholders. The stakeholder’s participation is essential to define the vision of the future system and to set the sustainability targets. For its demonstration task, TRUST includes a complete simulation of the roadmap planning and of its implementation in real systems. Participating water companies are organized in clusters, each one characterized by a particular set of problems related to UWCS. In the following, we illustrate the roadmaps developed by cities involved in the water scarcity cluster