Energy Metrics for Water Distribution System Assessment: Case Study of the Toronto Network

Abstract

Descriptive energy metrics, calculated for each component, represent how the hydraulic state of a network evolves and how energy flows vary temporally and spatially. More specifically, these metrics describe how the energy supplied is partitioned between the energy that is dissipated, lost, and delivered throughout the system. The metrics are meant to support planning, from local (e.g., pump or pipe renewal) to system-wide (e.g., leakage or pressure management) decisions. Whereas aggregate results are indicators of system capacity, efficiency, greenhouse gas emissions, and costs, the comparison of component metrics allows for the identification of specific pipes, tanks, or pumps for which changes would be most beneficial. Furthermore, analysis of the temporal variation of energy flows facilitates the assessment of operation under multiple scenarios. The metrics are applied to a case study of the Toronto water distribution system and show, based on two scenarios provided by Toronto Water, that on average, less than 27% of the energy supplied is actually delivered to users. This system inefficiency has important economic and environmental repercussions. Nevertheless, changes to operations, such as improved pump maintenance or scheduling, have significant potential to lower costs and exploit lower greenhouse gas emission factors.