Research Objectives and Topics

　It is alleged that the 21st century is the "century of water." Wars over water might happen like over oil that occurred in the last century. The rapid increase in population and the coming global climate change could be cause of water scarcity. This project attempts to develop global perspectives of such water resource issues by integrating field observations, predicting natural water cycles and human's water usage in the future, and by establishing guidelines for

sustainability development from the viewpoint of water resource issues.

　The population increase, expected mainly in developing countries, increases water demand, resulting in more intense use of water resources in the world. For Japan or European countries, water resources issues will also be serious; for example, decreased water resources due to global climatic change, inappropriate water management and deteriorated water quality. Therefore, water issues are currently considered to be one of the most critical problems in

the world.

　Although much information about water issues is now available, it seems there is no academic conclusion of the information. And it is also a problem that only a little information is dispatched by Asian countries including Japan;most information is actually dispatched by the U.S. and European countries.

　This project aims at clarifying the true nature of world water issues mentioned above and showing perspectives of the current situation of global water cycles and resources, and making projections of future global water resources and stress". Also it aims "to pursue an integrated approach between social and natural sciences to deal with some specific water issues considered as a part of world water crisis.

Progress of the Project

　Regarding the primary goal, we have succeeded in positing our research as cutting-edge in the world with the finest estimation and projection of global water cycles and resources. As a result, Dr. Taikan Oki, the former leader and a currently core member, was chosen as a lead author of the IPCC AR4 and the Millennium Assessment. Also our paper in Science has promoted effectively the achievement of this project (Oki and Kanae 2006).

　We, hereafter, describe the details. First, regarding the global water circulation, we successfully reproduced the daily fluctuation of land hydrological cycles through the past 100 years for the first time in the world (Hirabayashi et al., 2005). Second, we made a projection of land hydrological cycles for the next 100 years. Third, current and future water demands were estimated. In making projections, we mostly apply the grid scale of 1 degree or 0.5 degree as horizontal resolution at a global scale. Then we calculate the current and future water stress in a global scale through an integration of all the estimations above (Oki and Kanae, 2006).

　As a result, the following three points are shown: (i) over 2 billion people are under physically high water stress; (ii) the number of people under the stress will increase in the future. What is more important, however, is that we can control the rate of increase; and (iii) as long as water stress, the current or the near future in the next several decades is more critical than the distant fixture.

　Conventional water resources assessment did not include the trade in virtual water, i.e. the amount of water that is embedded in food or other products needed for its production. We successfully estimated the amount of virtual water trade of the world for the previous several decades. Here, two main findings are addressed (Oki and Kanae, 2004): (i) the amount of virtual water trade accounts for no less than 10% of the total direct water intake; and (ii) Japan imports the largest amount of the virtual water in the world. The implication of findings is so influential in Japan that it has taken a sort of leading role through several mass media and trade books in the enlightenment about global water problem in its public sphere. Perhaps, the projection of virtual water would be expected. At this moment, however, we skip the projection to avoid an infeasible projection.

　And moreover, we conducted specific case studies on Asia and California. Particularly it should be noted that the latter case provides us a fruitful outcome, which tend to be overlooked in global scale analysis. California is one of the water-deficient areas that we estimate "the hot spot". We paid attention to water management policy in California to look for a countermeasure for global water crisis. Among others, we put focus on a system of water transaction named "water bank" that had been introduced in 1991 to cope with severe drought, with special reference to the legal framework, effectiveness, and problems. As a result, we concluded that "soft-path" solution such as law and institution as well as "hard-path" solution such as dam can be effective tools against water deficit problem.

 Relation with Research Program

　The "Conceptual Framework for Global Environmental Issues" is a relatively new axis which was changed from "Integration" in this institute. Since this project has been attempting to develop a new concept and new information related to global water issues, this change is very relevant for us. Quantification of "virtual water", one of the main outcomes of this project, needs to be investigated more in deep from the viewpoint of its concept. It will be a next subject in near future, and probably will be a good topic among the projects in the program.