Water Use Model for Quantifying Environmental and Economic Sustainability Indicators

A systems approach is used to model the urban water cycle. A model for analyzing the flows of water, energy, and chemicals and associated greenhouse gas emissions through the urban water infrastructure system is developed. A model is constructed to represent the City of Toronto urban water system from 2001 up to the year 2010. Scenarios are developed to assess the system-wide impacts of water distribution pipe renewal, sewer relining, demand management strategies, and energy recovery from anaerobically digested wastewater biosolids. Initiatives targeted at the early stages of the urban water cycle have greater positive downstream impacts on selected environmental indicators. Specifically, strategies aimed at reducing water demand produce more significant system-wide benefits. Demand management strategies aimed at reducing demand by 15% result in savings on the order of 12–18% for all environmental indicators. Demand management is also one of the most cost effective options.