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Hydrology and Earth System Sciences An interactive open-access journal of the European Geosciences Union
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Volume 12, issue 4 | Copyright
Hydrol. Earth Syst. Sci., 12, 1027-1037, 2008
https://doi.org/10.5194/hess-12-1027-2008
© Author(s) 2008. This work is distributed under
the Creative Commons Attribution 3.0 License.

  29 Jul 2008

29 Jul 2008

An integrated model for the assessment of global water resources – Part 2: Applications and assessments

N. Hanasaki1, S. Kanae2, T. Oki2, K. Masuda3, K. Motoya4, N. Shirakawa5, Y. Shen6, and K. Tanaka7 N. Hanasaki et al.
  • 1National Institute for Environmental Studies, Japan
  • 2Institute of Industrial Science, University of Tokyo, Japan
  • 3Frontier Research Center for Global Change, Japan
  • 4Faculty of Education and Human Studies, Akita University, Japan
  • 5Graduate School of Systems and Information Engineering, University of Tsukuba, Japan
  • 6Center for Agricultural Resources Research, The Chinese Academy of Sciences, China
  • 7Disaster Prevention Research Institute, Kyoto University, Japan

Abstract. To assess global water resources from the perspective of subannual variation in water availability and water use, an integrated water resources model was developed. In a companion report, we presented the global meteorological forcing input used to drive the model and six modules, namely, the land surface hydrology module, the river routing module, the crop growth module, the reservoir operation module, the environmental flow requirement module, and the anthropogenic withdrawal module. Here, we present the results of the model application and global water resources assessments. First, the timing and volume of simulated agriculture water use were examined because agricultural use composes approximately 85% of total consumptive water withdrawal in the world. The estimated crop calendar showed good agreement with earlier reports for wheat, maize, and rice in major countries of production. In major countries, the error in the planting date was ±1 mo, but there were some exceptional cases. The estimated irrigation water withdrawal also showed fair agreement with country statistics, but tended to be underestimated in countries in the Asian monsoon region. The results indicate the validity of the model and the input meteorological forcing because site-specific parameter tuning was not used in the series of simulations. Finally, global water resources were assessed on a subannual basis using a newly devised index. This index located water-stressed regions that were undetected in earlier studies. These regions, which are indicated by a gap in the subannual distribution of water availability and water use, include the Sahel, the Asian monsoon region, and southern Africa. The simulation results show that the reservoir operations of major reservoirs (>1 km3) and the allocation of environmental flow requirements can alter the population under high water stress by approximately −11% to +5% globally. The integrated model is applicable to assessments of various global environmental projections such as climate change.

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