Hoff,H., Falkenmark,M., Gerten,D., Cordon,L., Karlberg,L. and Rockstrom(後のoの頭に¨),J.(2010): Greening the global water system. Journal of Hydrology, 384, 177-186.

『世界の水システムをグリーン化する』


Summary
 Recent developments of global models and data sets enable a new, spatially explicit and process-based assessment of green and blue water in food production and trade. An initial intercomparison of a range of different (hydrological, vegetation, crop, water resources and economic) models, confirms that green water use in global crop production is about 4-5 times greater than consumptive blue water use. Hence, the full green-to blue spectrum of agricultural water management options needs to be used when tackling the increasing water gap in food production. The different models calculate considerable potentials for complementing the conventional approach of adding irrigation, with measures to increase water productivity, such as rainwater harvesting, supplementary irrigation, vapour shift and soil and nutrient management. Several models highlight Africa, in particular sub-Saharan Africa, as a key region for improving water productivity in agriculture, by implementing these measures.
 Virtual water trade, mostly based on green water, helps to close the water gap in a number of countries. It is likely to become even more important in the future, when inequities in water availability are projected to grow, due to climate, population and other drivers of change.
 Further model developments and a rigorous green-blue water model intercomparison are proposed, to improve simulations at global and regional scale and to enable tradeoff analyses for the different adaptation options.

Keywords: Green/blue water; Virtual water; Crop water productivity; Irrigated/rainfed agriculture; Africa; Global model intercomparison』

Introduction
Box 1
The models
Main findings
 Dominance of green water in food production
 Overexploitation of water resources
 Current and future water productivity/virtual water content
 Adaptation options to increasing water scarcity and for food security
  Intensification on existing agricultural land
   Irrigation
   Rainwater harvesting, storage and supplementary irrigation
   Improved soil and water management
   Investment in agricultural water management
  Area expansion onto non-agricultural land
  Virtual water trade
 Green and blue water use and potential in Africa
Discussion
Conclusions
References


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