Ecological network analysis of an urban water metabolic system based on input-output model: A case study of Guangdong, China.

When considering a region as a superorganism, there are various processes of metabolism that reflect the growth and maintenances of the system, as well as the interactions with the surroundings. Ecological Network Analysis combined with the input-output model is utilized to analyze the water consumption structure and the interaction control relationships among different sectors within the urban ecosystem. The integrated approach is applied to the case study of Guangdong Province, China. The Water Ecological Network model is developed by the monetary I-O table of Guangdong province in 2012. The network control analysis is employed to describe the pathway of indirect water. In addition, the competitive and mutual relationship among different sectors is concluded by the approach of network utility analysis. This study also newly compares "virtual water (which is the indirect water) imports of per unit Gross Domestic Product (GDP)" and "water consumption of per unit GDP" to reveal which of them contributes more to the urban metabolism. The results indicate that the top three controllers are machinery, equipment and other services, followed closely by food and tobacco processing. The model results also show that the negative effects among different sectors accounting for the majority in all relationships, which indicates that the system under investigation is not in a mutualism state. This is due to that the competition of water uses between the economic sectors weaken the virtual water circulation within the system. The results are valuable to provide scientific suggestions for improving water use efficiency and make reasonable virtual water policy.