Regional analyses of water use in Japanese paddy rice cultivation using modified water footprint indexes

Water use in paddy rice cultivation was evaluated from the perspective of the environmental impact of water resource consumption for seven regions in Japan. Water resources can be appropriately discussed on a flow basis, and the impact of water consumption depends on the available water flow, which varies largely by time and location, in addition to the amount of water consumption itself. In this study, differential and integral water footprints were used as the indexes for the analyses. These indexes were previously developed and can help draw conclusions regarding the continuous impact of consumption on the water resources on a flow basis, taking into account the regional and temporal conditions of water supply. The results showed that the impact of water consumption was higher in regions with less amount of river flow. In particular, a large variation of impact, with temporally high values, was observed in such regions. These results suggest the necessity of water management on the basis of not only total or average water flow, but also temporal variation.