Energy use for water provision in cities

Abstract

Energy demand for urban water supply is emerging as a significant issue. This work undertakes a multi-city time-series analysis of the direct energy use for urban water supply. It quantifies the energy use and intensity for water supply in 30 cities (total population of over 170 million) and illustrates their performance with a new time-based water-energy profiling approach. Per capita energy use for water provision ranged from 10 kWh/p/a (Melbourne in 2015) to 372 kWh/p/a (San Diego in 2015). Raw water pumping and product water distribution dominate the energy use of most of these systems. For 17 cities with available time-series data (between 2000 and 2015), a general trend in reduction of per capita energy use for water provision is observed (11%–45% reduction). The reduction is likely to be a result of improved water efficiency in most of the cities. Potential influencing factors including climate, topography, operational efficiency and water use patterns are explored to understand why energy use for water provision differs across the cities, and in some cities changes substantially over time. The key insights from this multi-city analysis are that i) some cities may be considered as benchmarks for insight into management of energy use for water provision by better utilising local topography, capitalising on climate events, improving energy efficiency of supply systems, managing non-revenue water and improving residential water efficiency; ii) energy associated with non-revenue water is found to be very substantial in multiple cities studied and represents a significant energy saving potential (i.e. a population-weighted average of 16 kWh/p/a, 25% of the average energy use for water provision); and iii) three Australian cities which encountered a decade-long drought demonstrated the beneficial role of demand-side measures in reducing the negative energy consequences of system augmentations with seawater desalination and inter-basin water transfers.