Evaluation of external virtual water export and dependency through crop trade: an Asian case study

Abstract

The aim of this study was to evaluate virtual water export through five crops (barley, rice, maize, soybeans, and wheat) in terms of the external virtual water rate, within and outside of Asia from 2000 to 2012, and in comparison with that within and outside the European Union (EU). The external virtual water rate indicates the proportion of virtual water export outside of a boundary. Approximately 46.9% of the green water exports and 40.9% of the blue water exports were discharged from Asia to non-Asian countries. For example, Thailand, which is the main exporter in Asia, exported 55.5% of the total virtual water exported to non-Asian countries, and Kazakhstan exported 63.8% of the total virtual water exported to European countries. In comparison, the external virtual water rate for the EU was 30.2% (green water) and 25.2% (blue water). The virtual water trade is also important to the main importers in Asia. We evaluated the virtual water dependency on exporters in East Asia of Japan, Korea, and Taiwan. These three countries have a high dependency on virtual water imported from only a few exporters; thus, they should extend their virtual water trade boundary to include additional exporters. These results provide information necessary for the development of an integrated water strategy in Asia, and could convince the main Asian importers of the risks of serious dependency on foreign water resources.