A path-based structural decomposition analysis of Beijing’s water footprint evolution

The Water Footprint (WF) is a popular and useful indicator for evaluating regional water use situations. The Structural Decomposition Analysis (SDA) method is able to break down the changes in water usage according to its determinants. There is a lack of the framework for comprehensively understanding a regional water situation for long period of time. The challenge lies in the facts of the incomplete WF evaluations and the static and non-uniqueness issues of SDA. In this paper, a path-based SDA (PB-SDA) model is proposed to address the SDA issues, which is further utilized to decompose the changes of the WF in Beijing. By employing an input–output-based WF analysis method, the sectoral WFs of Beijing are computed using the 1987–2007 data, in which the exported Virtual Water (VW) is evaluated in particular. Results show that during 1987–1997, Beijing’s exported VW decreased significantly due to the export restructuring, which helped to reduce local water pressure. The internal WF continuously decreased during 1987–2007, and the external WF increased during 1997–2007, both of which indicated that Beijing had become increasingly dependent on external water. The decomposition results indicate that the technological effect is the dominant contributor with 48 % of the total contribution contributing to the WF decrease. The structural effect, which is related to the final demand restructuring, contributed 6 % of the contribution to the WF decreases during 1997–2007, as well as to the increases of WF during 1987–1997. The other components that contributed to the WF increases were the consumption level (35 %) and population (10 %) effects, caused by the increasing living standards and an expanding population during this period. This work also shows that the PB-SDA model has an advanced dynamic property, as well as the uniqueness and rationality of decomposition results. The methodology serves as a decision-making support, and it is universally adaptable in other regions. The findings in our study case are able to provide better understanding about the water situation, as well as the references to better manage water resources in other regions.