Increasing population pressure, natural climate variability and susceptibility to projected climate change impacts are placing ever-increasing strain on existing water infrastructure in Australia. This water infrastructure has generally focused on meeting urban water demand via a range of ‘low-energy’ approaches predominantly based on the capture and storage of surface runoff; however, this approach is proving to be no longer sufficient to satisfy the increasing urban water demand.

Water service providers have been seeking to minimise supply risk through systems approaches such as demand management but more importantly through the implementation of a diverse range of energy-intensive climate-independent solutions. To date, water service providers have investigated numerous options and implemented a range of alternative water sources such as desalination, groundwater extraction, pipeline distributions and recycling schemes. These water sources, however, rely on technologies that are significantly more advanced and/or have much higher operational energy costs, and to date, many attempts to address emerging water supply problems in Australia have come at an increased economic and environmental cost.

Detailed assessments and understanding of the ‘water–energy nexus’—the interactive relationship between water and energy—are crucial precursors to enable the water sector to reduce its operational energy costs and facilitate the design of water and energy systems capable of realising any synergistic benefits. Under the current paradigm, in which energy supply and pricing issues are becoming increasingly important in the public sphere, having an improved understanding of this linkage will allow water service providers to be more aware of the energy impacts of key water infrastructure and be more responsive to future changes in the cost of their energy supplies.

This discussion paper looks at options for securing Australia’s urban water supply through addressing the water–energy nexus and current energy requirements and associated operational energy costs for a number of important water and wastewater treatment technologies. Additionally, a review of various water supply options currently implemented by water service providers is presented from an energy perspective. Finally, system management approaches as well as other alternative low- energy water supply or savings options are discussed.

This paper was motivated by the Australian Federal Government climate change adaptation initiatives. The authors are members of the Australian Climate Change Adaptation Research Network for Settlements and Infrastructure (ACCARNSI), one of eight networks within the National Climate Change Adaptation Research Facility (NCCARF).