To improve the actual urban water system in la Vall de Boí in order to achieve a more sustainable model. By analysing a selected material and energy flows as well as a selected environmental impacts associated with the metabolism of the urban water system, a study of the current sustainability level will be done with a MFA-LCA approach. Then, certain interventions based on sustainable development will be studied and compared with specific KPIs for each intervention and in relation with the current situation.

The upcoming sustainability challenges in the urban water systems are driving management and planning focus towards sustainability in a more holistic and integrated view. In this work, the Dynamic Metabolism Model (DMM), based on the LCA and MFA approach, has been used to analyse the inputs and outputs from the urban water system (UWS) metabolism to give sustainability assessment. It constitutes the first step to achieve a full internalisation of costs of the UWS. This model has been carried out in a real case study in the Vall de Boí, Pyrenees, Spain. The present analysis, as well as future interventions and scenarios, are developed after consulting stakeholders involved. The impact assessment has shown that the greatest impact is the in-house and the WWTPs energy demand, so the interventions have been designed to overcome them reducing them, designing green infrastructure and using ICTs to improve the efficiency of the current assets. In this work, an integral solution has been also designed modelling water policies to understand their impacts on the UWS thanks to specific calculated KPIs. The DMM has been demonstrated as a powerful tool to comprehensively understand the impacts of specific interventions strategies that can usefully help stakeholders into the decision-making process. The results of the improvement assessment showed a reduction up to 24% of the GWP and AP impacts, and up to 49% of the EP impacts. The results also show that a sustainable urban water planning and policy, decoupled from the economic dimension can be achieved while demonstrating that can represent an opportunity to reduce costs and generate business too.