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Water and energy are important factors that must be addressed to achieve sustainable urban development, and are inextricably linked. With the development of urbanization and the utilization of unconventional water sources, the energy consumption of urban water systems may dramatically increase, and the urban greenhouse gas emission may also increase.

Through the case analysis of Qingdao City, we find that:

1. The shortfall between Qingdao’s water demand and water resources will continue to grow along with socio-economic development, and the biggest contributor to this will be the growth in urban domestic water use;
    
2. Qingdao must exploit unconventional water resources (including reclaimed water, and seawater desalination) if it is to solve its water demand problem. Choice of water source allocation will have a direct impact on the energy consumption and carbon emissions of the urban water system. To meet drinking water quality standards, of the water sources available for Qingdao, the energy consumption is between 0.426 and 4 kWh per cubic meter. In order of increasing energy, the water sources are: local surface water < water diversion (Yellow River) < groundwater < NEWater < water diversion (Yangtze River) < desalination of brackish water < seawater desalination. As the most energy-intensive, seawater desalination has an energy consumption per unit of water supply which is 10 times larger than that of local surface water.
    
3. Qingdao’s urban water system faces an inevitable rise in energy intensity and carbon emissions. It must incorporate carbon accounting and energy management into its water supply planning to help it reduce the urban water system’s carbon footprint allowing it to pursue low-carbon sustainable development.
    
4. Qingdao does not only need to consider factors such as cost and continuity of supply when deciding on a water source allocation mix, it also needs to thoroughly consider the type of water source, energy consumption per unit of water supply, carbon emissions, and environmental risks etc.
    
5. Qingdao should reform its water tariff and continue prioritizing water saving measures.