Where is the future for a growing metropolis in North China under water resource constraints?

Rapid progress of economic development and urbanisation has created a water demand crisis in the Beijing–Tianjin metropolis in North China. This study evaluates the metropolis’s carrying capacity under water resource constraints by examining the discrepancies between the actual water requirements, water usage and the locally available water resources; the water footprint (WF) approach is used to assess associated changes in these variables. A structural decomposition analysis is applied to decompose the driving factors of the increasing water requirements in the Beijing–Tianjin metropolis. The results indicate that the increasing actual water requirements are far greater than the increase in the locally available water resources and water usage, especially in Beijing. The discrepancy between the actual water requirements, locally available water resources and water usage sharply increased from 2002 to 2007, which introduced a serious water crisis and more significant constraints on the water resources. The carrying capacity was based on freshwater transfer, groundwater extraction and VW trade. Four separate factors are considered to contribute to the effects of actual water requirement changes from 2002 to 2007: technological improvements, economic system efficiency, scale effect and consumption structure changes. Significant water saving efforts via technological improvement have been made in the Beijing–Tianjin metropolis in the past. However, these improvements could not cover the increasing actual water requirements driven by economic and population growth. To address the two challenges (i.e. regional development and the water shortage) and to enhance the carrying capacity in terms of sustainability in the future, the Beijing–Tianjin metropolis should adopt a more active role in controlling the growth of population and increasing the WF. Although increased water resources and interregional virtual water trades with other regions have greatly contributed to alleviating the water crisis in recent years in the Beijing–Tianjin metropolis, the water saving potential may be realised through the readjustment of industrial structure, consumption structure, urban spatial structure and economic instruments in the future.