Water footprints, or the total consumed water to produce commodities, were estimated for imported food to Japan, using an integrated global water resources model that consists of a physically based hydrological module and a crop growth module. In order to analyze the sustainability of water resources, the model was enhanced to quantify four major sources: precipitation, river, reservoirs, and non-renewable groundwater. The results showed that the water footprint of Japan was 42.7km3/yr. The virtual water, or the required amount of water that is needed to produce the imported food domestically, was estimated 62.7 km3/yr. Therefore, it indicates 20.0 km3/yr of water was saved through international trades. Among the total water footprint, 7.3 km3/yr (17%) was originated irrigation water, and 2.9 km3/yr (6.8%) was non-renewable groundwater.
Virtual water trade, global water resources assessment