Modelling metabolism based performance of an urban water system using WaterMet2

• WaterMet2 presented as a simulation model for urban water system (UWS).
• The model quantifies metabolism and sustainability based performance of the UWS.
• The model quantifies complex water-energy and associated environmental impacts.
• The model can be used for evaluating intervention strategies in UWS planning.
• The model is demonstrated for strategic planning of a real world case study.

This paper presents a new quantitative model called ‘WaterMet2’ for the metabolism based assessment of the integrated urban water system (UWS) performance. WaterMet2 quantifies a number of UWS flows/fluxes (e.g. water and energy) which can be used to derive sustainability-based performance metrics. The generic WaterMet2 model overcomes the drawbacks of the existing UWS models and strives to bridge the gaps related to the nexus of water, energy and other environmental impacts in an integrated UWS. The main features of WaterMet2 are: (1) conceptual simulation model of UWS comprised of water supply, stormwater and wastewater subsystems with possible centralised and decentralised water reuse; (2) UWS represented by an arbitrary number of key UWS components for each type in four spatial scales (System, Subcatchment, Local and Indoor areas) in a distributed modelling type approach; (3) quantifying the metabolism-based performance of UWS including the caused and avoided environmental impact categories (GHG emissions, acidification and eutrophication potentials) and resource recovery in UWS. WaterMet2 is tested, validated and demonstrated by evaluating the long-term performance of the UWS of a northern European city for three states including business as usual and two intervention strategies: addition of new water resources and large scale localised water recycling. The results obtained demonstrate the effectiveness of WaterMet2 in evaluating the sustainability related UWS performance, the suitability of using WaterMet2 at the strategic level UWS planning and the importance of using an integrated assessment approach covering the full urban water cycle.