Greening the global water system

• Published in: Journal of hydrology (Amsterdam) Vol. 384; no. 3; pp. 177 - 186
• Main Authors: Hoff, H., Falkenmark, M., Gerten, D., Gordon, L., Karlberg, L., Rockström, J.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 30.04.2010; [Amsterdam; New York]: Elsevier
• Subjects: Africa; agricultural management models; agricultural water management; Assessments; blue water use; crop production; Crop water productivity; Crops; dryland farming; Economics; environmental models; food production; Foods; global hydrologic models; Global model intercomparison; green water use; Green/blue water; hydrologic models; Hydrology; irrigated farming; Irrigated/rainfed agriculture; Irrigation; irrigation water; NATURAL SCIENCES; NATURVETENSKAP; Productivity; simulation models; Vegetation; Virtual water; virtual water trade; water management; water policy; water resources; water use; Sub-Saharan Africa; Africa; Global model intercomparison; Green/blue water; Virtual water; Crop water productivity; Africa; Irrigated/rainfed agriculture
• ISSN: 0022-1694; 1879-2707; 1879-2707
• DOI: 10.1016/j.jhydrol.2009.06.026

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.