The changing nature of the water–energy nexus in urban water supply systems: A critical review of changes and responses

This paper provides a review of the changing nature of the water–energy nexus in urban water supply systems (UWSSs) due to the primary long-term drivers of climate change, population growth and technological development from the ‘energy for water’ perspective. We identify both the physical changes in UWSSs, as well as the changes in the attributes of the system, both of which contribute to the changing nature of the water–energy nexus. We provide an overview of responses to this change in the water–energy nexus through the lens of four application areas, namely long-term planning, system design, system operation and system rehabilitation, based on the review of 52 papers. Ten responses in three categories are found to be commonly considered in each of the four application areas. The three categories are energy or greenhouse gas reduction, integrated modelling and planning, and improving social benefits. The main drivers of these responses may vary with the application area. Based on the review outcomes, we outline the gaps in the responses in relation to the changing nature of the water–energy nexus in UWSSs, providing directions for future research on improving UWSS efficiency considering the long-term drivers.