Most cities import energy and water from their hinterlands. Both the nexus in a city and that between the city and its hinterlands should be considered for comprehensive management of water and energy. To examine the water-energy nexus associated with the city embedded in the hinterland, a city-hinterland water-energy mixed-unit input-output methodology is proposed to model the effects of growth under different water and energy production and consumption scenarios based on the growth of the demands for water and energy resources from the city. This study presents a demonstration of the water-energy mixed-unit input-output approach by analyzing Hong Kong and its associated hinterland in mainland China. A Sankey diagram and several indicators have been presented to illustrate the water-energy nexus in 2015, as well as the nexus for future city growth and the nexus incorporating the water and energy infrastructures planned in Hong Kong. Several indicators in the results compare the interaction between water and energy systems and the dependence on hinterland for different scenarios in Hong Kong. The modeling outcomes show that the current water infrastructures might be able to meet the demand for water treatment in 2050. The indicators obtained from this study suggest that all types of water for energy and energy for water will increase by 7.8-9%.