HR: 16:45h
AN: GC34A-04    [Abstracts]
TI: Global Water Resources Under Future Changes: Toward an Improved Estimation
AU: * Islam, M
EM: s_islam@iis.u-tokyo.ac.jp
AF: Oki & Kanae Laboratory, IIS, The University of Tokyo, 4-6-1 Komaba, Meguru-Ku, Tokyo, 153-0041 Japan
AU: Agata, Y
AF: Oki & Kanae Laboratory, IIS, The University of Tokyo, 4-6-1 Komaba, Meguru-Ku, Tokyo, 153-0041 Japan
AU: Hanasaki, N
AF: Oki & Kanae Laboratory, IIS, The University of Tokyo, 4-6-1 Komaba, Meguru-Ku, Tokyo, 153-0041 Japan
AU: Kanae, S
AF: Oki & Kanae Laboratory, IIS, The University of Tokyo, 4-6-1 Komaba, Meguru-Ku, Tokyo, 153-0041 Japan
AU: Oki, T
AF: Oki & Kanae Laboratory, IIS, The University of Tokyo, 4-6-1 Komaba, Meguru-Ku, Tokyo, 153-0041 Japan
AB: Global water resources availability in the 21st century is going to be an important concern. Despite its international recognition, however, until now there are very limited global estimates of water resources, which considered the geographical linkage between water supply and demand, defined by runoff and its passage through river network. The available studies are again insufficient due to reasons like different approaches in defining water scarcity, simply based on annual average figures without considering the inter-annual or seasonal variability, absence of the inclusion of virtual water trading, etc. In this study, global water resources under future climate change associated with several socio-economic factors were estimated varying over both temporal and spatial scale. Global runoff data was derived from several land surface models under the GSWP2 (Global Soil Wetness Project) project, which was further processed through TRIP (Total Runoff Integrated Pathways) river routing model to produce a 0.5x0.5 degree grid based figure. Water abstraction was estimated for the same spatial resolution for three sectors as domestic, industrial and agriculture. GCM outputs from CCSR and MRI were collected to predict the runoff changes. Socio-economic factors like population and GDP growth, affected mostly the demand part. Instead of simply looking at annual figures, monthly figures for both supply and demand was considered. For an average year, such a seasonal variability can affect the crop yield significantly. In other case, inter-annual variability of runoff can cause for an absolute drought condition. To account for vulnerabilities of a region to future changes, both inter-annual and seasonal effects were thus considered. At present, the study assumed the future agricultural water uses to be unchanged under climatic changes. In this connection, EPIC model is underway to use for estimating future agricultural water demand under climatic changes on a monthly basis. From the estimation of present stress level (withdrawal to resource ratio), the months between January to May was found to have the highest number of population above water stress level, while the months between June to August having lower population in stress. The regions suffering from high seasonal variability are those of Asian monsoon zone, south-central Africa and central-east part of South America. Inter-annual variability, on the other hand, is dominant mostly along the Middle-east or Sahara regions and the western part of South America and Latin America. Virtual water trading among countries was estimated on per capita basis. It shows that many Middle east countries are able to compensate their water stress significantly through virtual water trading. The overall effect of climate change on lowering of river runoff mostly affected Europe, southern part of China and Latin America. India or Central Africa have better runoff availability under changing climate, but still subject to a higher water stress because of socio-economic factors like high population growth and expected increase in rate of water uses. Decrease in population as well as saturation level of maximum water uses along most European countries, on the contrary, relaxed the pressure of lowering river runoff, causing no significant change in future stress.
DE: 1600 GLOBAL CHANGE (New category)
DE: 1630 Impact phenomena
DE: 1884 Water supply
SC: Global Climate Change [GC]
MN: 2005 Joint Assembly